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THE ECOLOGICAL CONTEXT OF THE EARLY PLEISTOCENE HOMININ DISPERSAL TO ASIA
by Robin Louise Teague
A.B. in Anthropology, 2001, Harvard University
A dissertation submitted to
The Faculty of The Columbian College of Arts and Sciences
of The George Washington University in partial fulfillment of the requirements for the degree of Doctor of Philosophy
August 31, 2009
Dissertation directed by
Richard Potts Curator of Physical Anthropology,
National Museum of Natural History, Smithsonian Institution
Alison S. Brooks Professor of Anthropology
UMI Number: 3366726
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The Columbian College of Arts and Sciences of The George Washington University
certifies that Robin Louise Teague has passed the Final Examination for the degree of
Doctor of Philosophy as of June 16, 2009. This is the final and approved form of the
dissertation.
THE ECOLOGICAL CONTEXT OF THE EARLY PLEISTOCENE HOMININ DISPERSAL TO ASIA
Robin Louise Teague
Dissertation Research Committee:
Richard Potts, Curator of Physical Anthropology, National Museum of
Natural History, Smithsonian Institution, Dissertation Co-Director
Alison S. Brooks, Professor of Anthropology, Co-Director
Lars Werdelin, Senior Curator, Swedish Museum of Natural History,
Committee Member
iii
Copyright 2009 by Robin Louise Teague All rights reserved
iv
Acknowledgments
I would like to acknowledge a number of people who have helped me and guided
me through the process of writing my dissertation. First, I would like to thank my
committee: Rick Potts, Alison Brooks, Lars Werdelin, Margaret Lewis and Brian
Richmond. My advisor, Rick Potts, led me into a stimulating area of research and
supported me in pursuing a large and ambitious project. He has encouraged me all
through the time I have worked on this dissertation. Alison Brooks has helped me with
enthusiasm, pointing out differing perspectives and opportunities. Lars Werdelin has been
a source of detailed and helpful information and has always been available to answer
questions and provide guidance. I am also grateful to Brian Richmond and Margaret
Lewis for many helpful comments and for making time for my dissertation.
I would also like to thank my family for their love and support during my time in
graduate school and especially during the process of writing. Their encouragement was
essential to my success.
I would like to thank my fellow students at GWU for many years of friendship. I
would like to thank that faculty of the Hominid Paleobiology Doctoral Program and the
Department of Anthropology for their support. At the Smithsonian, I thank Jenny Clark,
Briana Pobiner and Matt Tocheri for their assistance and for making me feel welcome.
For access to mammalian skeletal collection, I thank Linda Gordon. I am also grateful to
the Smithsonian Libraries for letting me check out and renew many books many times.
v
Thanks go also to the many people who facilitated my access to fossils at the
Kenya National Museum and the Institute of Vertebrate Paleontology and
Paleoanthropology in Beijing, as well as many other museums. In particular, Wang Wei
traveled with me, assisting with translation and helping me make the contacts necessary
to study many of the fossil specimens in Chinese museums. I would also like to thank
Gao Xing, Deng Tao, Qiu Zhanxiang, Qi Guoqin, Huang Weiwen, Hou Yamei, Zhu
Rixiang, Deng Chenglong, Li Qing Kui and Wei Guangbao for helping me study fossil
specimens while I was in China.
For financial support, I would like to thank the IGERT program in Hominid
Paleobiology at GWU as well as the Smithsonian National Museum of Natural History
where I had a predoctoral fellowship. My years of study at GWU and at the Smithsonian
Human Origins Program have been extremely rewarding. This dissertation research was
funded by NSF Grant BSC 065092.
vi
Abstract of Dissertation
The Ecological Context of the Early Pleistocene Hominin Dispersal to Asia
The ecological context of the first known dispersal of Homo into East Asia is
investigated here using information from large mammals, and particularly from
carnivores. The aims were to determine whether hominins occurred in similar ecological
contexts compared with sites in East Africa, and whether carnivore guilds in East Asia
and East Africa were similar in composition in terms of ecologically comparable species.
To answer these questions, dental measurements were taken on large mammalian
specimens from East Asian Plio-Pleistocene sites, including hominin and non-hominin
sites, and from specimens found at Olduvai Gorge and Lake Turkana in East Africa.
Dental measurements were taken to estimate body mass and hypsodonty, as well as
ecomorphological characteristics in carnivores. Each large mammal species was
classified as an ecotype, which is a combination of body mass, diet and substrate (i.e.,
terrestrial, arboreal and aquatic) characteristics. The ecotype analysis shows that East
Asian and East African fossil sites were significantly different from each other in
ecological structure, with the Asian sites having a greater concentration of browsers and
mixed feeders, while East African sites had more grazers. The East Asian hominin sites
included varied ecological structures, implying that hominins were not tied to a single
type of environment on their initial dispersal. Carnivore ecomorphological indices related
to body mass and feeding adaptations, such as the amount of the dentition devoted to
slicing, grinding and bone-cracking. Carnivore guilds containing sets of species with
similar feeding adaptations and body mass would have presented similar opportunities for
vii
scavenging and degrees of competition for hominins. The Hyaenidae differed between
Africa and Asia in features related to fourth premolar size. Omnivorous ursids were
present in Asia but not in Africa. In East Asia, there were also decreases in the number of
species of Hyaenidae and Canidae from the Late Pliocene to the early Pleistocene.
Despite this, the remaining Asian hyaenid, Pachycrocuta, would have been a formidable
competitor for scavenging hominins. Overall, hominins occurred in varied ecological
settings, and competed with a carnivore guild that had species with different adaptations
compared with Africa.
viii
Table of Contents
Acknowledgments....iiv
Abstract of Dissertation.vi
Table of Contents... .viiii
List of Figures....ix
List of Tablesxii
Chapter 1: Introduction..1
Chapter 2: Background to ecological similarity analysis.11
Chapter 3: Methods to determine ecological similarity....41
Chapter 4: Results of the ecological structure analysis....94
Chapter 5: Background to carnivore ecomorphology.....129
Chapter 6: Carnivore ecomorphology methods......151
Chapter 7: Carnivore ecomorphology results.....176
Chapter 8: Discussion.....236
Bibliography...270
Appendices.....292
ix
List of Figures
Figure 2.1 Map of East Asian fossils39
Figure 3.1 Modern Eurasian localities used for comparison.....52
Figure 3.2 Modern African localities used for comparison...53
Figure 4.1 Scatterplot of the CA of the modern faunal assemblages and ecotypes..........99
Figure 4.2 NMDS using Euclidean distance of modern divisions..100
Figure 4.3 CA scatterplot of modern faunal sites excluding rainforests....102
Figure 4.4 NMDS of modern sites excluding rainforests...104
Figure 4.5 Scatterplot of a CA of the modern sites and ancient fossil assemblages..109
Figure 4.6 Scatterplot of a CA of the modern and ancient assemblages, axes 2 and
3..110
Figure 4.7 NMDS analysis of ancient and modern sites.....112
Figure 4.8 CA scatterplot of modern and ancient faunal assemblages, excluding modern
rainforests....115
Figure 4.9 CA scatterplot, axes 2 and 3: Modern sites (excluding rainforests) and ancient
faunas......116
Figure 4.10 NMDS plot of Plio-Pleistocene assemblages with modern sites (excluding
rainforests)......120
Figure 4.11 Correspondence analysis scatterplot of Plio-Pleistocene sites125
Figure 7.1 Scatterplot of the CA for Canidae category scores...180
Figure 7.2 Scatterplot of NMDS analysis of Hamming distances for Canidae..181
x
Figure 7.3 PCA Scatterplot of Canidae index values from East Africa and East
Asia.182
Figure 7.4 Loadings for component 1 of the PCA of Canidae fossils........183
Figure 7.5 Loadings for component 2 of the PCA for Canidae fossils.......184
Figure 7.6 CA Scatterplot of Hyaenidae category scores.......189
Figure 7.7 NMDS scatterplot of Hyaenidae Hamming distances......190
Figure 7.8 PCA Scatterplot of Hyaenidae index values.........191
Figure 7.9 Component 1 PCA loadings for Hyaenidae..........192
Figure 7.10 Component 2 PCA loadings for Hyaenidae............193
Figure 7.11 CA Scatterplot of Felidae category scores...........201
Figure 7.12 NMDS scatterplot of Hamming distances for Felidae.....202
Figure 7.13 PCA Scatterplot of Felidae index values.........203
Figure 7.14 PCA loadings for component 1 for Felidae.........204
Figure 7.15 PCA loadings for component 2 for Felidae.............205
Figure 7.16 CA scatterplot of Ursidae category scores..........208
Figure 7.17 NMDS Scatterplot of Hamming distance values for Ursidae.............209
Figure 7.18 PCA Scatterplot of Ursidae index values210
Figure 7.19 Loadings for component 1 of PCA scatterplot for Ursidae.211
Figure 7.20 Loadings for component 2 of PCA scatterplot for Ursidae.212
Figure 7.21 CA Scatterplot of Mustelidae category scores.214
Figure 7.22 NMDS Scatterplot of Hamming distances for Mustelidae......215
Figure 7.23 PCA Scatterplot for index values for Mustelidae............216
Figure 7.24 PCA of Mustelidae loadings for component 1........217
xi
Figure 7.25 PCA of Mustelidae loadings for component 2218
Figure 7.26 CA Scatterplot of category scores for Herpestidae, Prionodontidae and
Viverridae...........221
Figure 7.27 NMDS Scatterplot of Hamming distances for Viverridae, Herpestidae and
Prionodontidae species...........222
Figure 7.28 PCA scatterplot of index values for Viverridae, Herpestidae and
Prionodontidae223
Figure 7.29 Component 1 loadings for PCA of Viverridae, Herpestidae and
Prionodontidae....224
Figure 7.30 Component 2 loadings for PCA of Viverridae, Herpestidae and
Prionodontidae225
Figure 7.31 Scatterplot of CA of carnivores from East Asia and East Africa232
Figure 7.32 Scatterplot of CA of carnivores from East Asia and East Africa, second and
third axes.........233
xii
List of Tables
Table 3.1 Ecotype classifications.....43
Table 3.2 Modern comparative localities.....48
Table 3.3 Plio-Pleistocene East Asian sites and their dates.56
Table 3.4 Plio-Pleistocene African species at the Turkana Basin and Olduvai...56
Table 3.5 Plio-Pleistocene East Asian species.....62
Table 3.6 Modern specimens of Canidae.75
Table 3.7 Modern specimens of Ursidae..76
Table 3.8 Modern samples of Mustelidae, Viverridae, Prionodontidae and Herpestidae
..76
Table 3.9 Ecological characteristics of East Asian fossil site faunas.......78
Table 3.10 Summary of ecological information and ecotype assignment for African fossil
species...83
Table 4.1 The MEDC (mean Euclidean distance to the centroid) for each modern
division..97
Table 4.2 Modern site group centroids excluding rainforests.........101
Table 4.3 Mean and maximum distance to the centroid for modern and ancient
assemblages.108
Table 4.4 Mean and maximum distance to the centroid for modern and ancient sites
excluding rainforests...117
Table 4.5 MANOVA results for the centroids of African and Asian fossil sites from the
ancient and modern CA without rainforests118
xiii
Table 4.6 Mean and maximum distance to the centroid for Plio-Pleistocene sites123
Table 4.7 MANOVA results for the centroids of African and Asian fossil sites.......124
Table 6.1 Modern Felidae samples.153
Table 6.2 Modern Hyaenidae samples........153
Table 6.3 Ecomorphological measurement descriptions........155
Table 6.4 Ecological traits and ecomorphological indices.155
Table 6.5 Index values for fossil carnivore species158
Table 6.6 Index values for fossil carnivore species, continued......162
Table 6.7 Category cut-off values.......167
Table 6.8 Category scores for all carnivores...................................................................171
Table 7.1 P-values for the MANOVA of carnivore family centroids in East Asia and East
Africa..226
Table 7.2 Mean distance to the centroid (MEDC) for carnivore families......227
Table 7.3 MEDC for carnivore guilds at African and Asian sites......227
Table 7.4 MANOVA of carnivore guilds at sites in Africa and Asia.....228
Table A6.1 Canidae specimens measured from East Asia.292
Table A6.2 Felidae specimens measured from East Asia...293
Table A6.3 Hyaenidae specimens measured from East Asia.295
Table A6.4 Ursidae specimens measured from East Asia......299
Table A6.5 Mustelidae specimens measured from East Asia.302
Table A6.6 Viverridae and Prionodontidae specimens measured from East Asia.303
Table A6.7 Canidae specimens measured from East African sites303
Table A6.8 Felidae specimens measured from East African sites..304
xiv
Table A6.9 Hyaenidae specimens measured from East African sites........305
Table A6.10 Mustelidae specimens measured from East African sites.........306
Table A6.11 Herpestidae specimens measured from East African sites........306
Table A6.12 Viverridae specimens measured from East African sites..307
1
Chapter 1: Introduction to the dissertation
Anthropologists have long been interested in the environments that hominins
inhabited and in the way hominins interacted with the other members of the mammalian
community, in particular with the large-bodied members of the order Carnivora
(carnivores). Large carnivore kills might have been scavenged by hominins for meat.
Carnivores interacted with hominins as predators, competitors, suppliers of scavengeable
carcasses, and later as sources of skins and ornamentation. The circumstances
surrounding the earliest currently known dispersal of hominins from Africa around 1.8
Ma are particularly interesting with regard to hominin ecology and interactions with other
mammals because the localities in which the dispersing hominins have been found (the
Caucasus, continental East Asia and Java) are geographically distant from Africa and
have taxonomically different faunas. The East Asian localities are in temperate and
subtropical zones, which would be expected to have a different ecology compared with
tropical and subtropical African sites. However, the comparative ecological contexts of
these locations are not well known.
The ecology of the localities in which dispersing hominins have been found is the
focus of this dissertation. The ecological context of hominin dispersal is addressed by
comparing the ecological properties of mammalian species from initial dispersal sites in
East Asia and contemporaneous sites in East Africa to determine whether hominins
colonized places that were ecologically similar or whether hominins were capable of
adapting to different environmental settings on their initial dispersal. A subset of the
study concerns carnivore feeding adaptations to determine whether the carnivore guilds
were similar in East Asia and East Africa, and if not, in what ways they differed. The
2
implications for resource and niche availability for hominins in new environments are
considered, as is the range of ecological contexts in which hominins were found in East
Asia and East Africa.
Current evidence points to an initial dispersal out of Africa around 1.8 Ma.
However, it is possible that hominins dispersed earlier and that new sites or new dates
will be found that push the date back further. Dmanisi is dated to 1.77-1.75, immediately
following the Olduvai subchron (Gabunia et al. 2000a, Vekua et al. 2002, and Rightmire
et al. 2006). The Yuanmou hominin layer is dated to ~1.7 Ma (Zhu et al. 2008), while the
oldest artifacts known from the Nihewan Basin are dated to ~1.66 Ma (Zhu et al. 2004).
Hominins in Java are dated to 1.8 to 1.6 Ma at Mojokerto (Swisher et al. 1994, 1997,
Larick et al. 2001, Huffman et al. 2006) and to ~1.6 Ma at Sangiran (Swisher et al. 1994,
Antn and Swisher 2004). These hominins were most likely members of the genus
Homo. Archaeological evidence from Africa and Asia indicates that Homo was most
likely an omnivore, obtaining meat from scavenging or predation. Dmanisi, sites within
the Nihewan and Yuanmou all have Oldowan stone tools.
The geographic spread of initial dispersal sites shows that hominins were able to
survive in regions very distant from East Africa, with mammalian faunas consisting of
many different genera and species. Dmanisi and the Nihewan Basin are located relatively
far north, at about 40N latitude, raising the possibility of that hominins had to adapt to
environmental conditions quite different from the tropical and subtropical latitudes
occupied by probable source populations.
3
Ecological Similarity of the Large Mammal Fauna
Environmental similarity has been thought to have facilitated hominin dispersal.
Dennell (2004) argued that a belt of savanna habitats across Asia and Africa provided
both environmental similarity and a wide corridor of ecologically suitable habitats for
hominins, resulting in dispersal into Asia. Dennell (2003, 2004) hypothesized that
hominins were constrained to environments that were sufficiently similar in temperature
and seasonality patterns to Africa, leading hominins to be only found south of 40N in
the early Pleistocene1. At Ubeidiya, the presence of Pelorovis was thought to imply the
extension of savannas, while Kolpochoerus may have indicated the occurrence of gallery
forests (Martnez-Navarro 2004). Dispersing hominins might have been part of a small
group of African taxa that expanded out of Africa at that time, implying that an
ecological opportunity, such as the expansion of suitable habitats, existed for certain
similar species (Turner 1999). Thus, the expansion of African savannas is thought to be a
facilitating factor for the initial hominin dispersal. However, there is evidence that some
of these sites are not similar in their faunal structure to that of African savannas.
Belmaker (2005) found that African savanna mammals were not abundant at Ubeidiya,
and that overall the faunal structure was more similar to that of Mediterranean
environments. Other than hominins, very few African species dispersed at this time into
Europe or Asia (Martnez-Navarro 2004), showing that it was unlikely that hominins
were part of a hypothetical group of African taxa entering East Asia simultaneously. The
hypotheses tested in this dissertation concern the degree to which environmental or
ecological similarity was an important factor in hominins ability to adapt to the new
1 Pleistocene and Pliocene are used to refer to their date range prior to June 29, 2009.
4
places they colonized. Each hypothesis is tested using data from the ecological properties
of large mammals.
1) Did the ecological settings and faunas associated with early Homo in East Asia
differ from those in East Africa at this time, and if so, in what ways?
2) Were there ecological differences between hominin and non-hominin sites in East
Asia?
The community or ecological structure of the mammalian fauna was evaluated
using ecostructure methods. In these methods, each species is classified using a
combination of ecological variables including body size, diet and substrate (i.e.,
terrestrial, arboreal or aquatic). Ecostructure methods have been used, for example, by
Andrews (1979, 1996), Reed (1997, 1998, 2008), Rodrguez 2004, 2006a, b), and
Mendoza (2004, 2005). Methods that classify species by ecological properties are
particularly useful in comparing sites with taxonomically different faunas in order to
determine how the sites were ecologically similar despite the taxonomic differences. This
type of method was used by Rodrguez (2004) to determine whether ecological change
was occurring along with taxonomic change at Atapuerca. Reed (1997, 1998, 2008) used
ecological classifications to reconstruct the paleoenvironments of hominins at
Makapansgat, Hadar and other East and South African sites. Ecostructure methods are
useful for comparison because they show which types of animals are the sources of
ecological similarity or difference between taxonomically different sites. The similarities
or differences between ancient East Asian and East African faunal assemblages are
5
described using the results of correspondence analysis and comparison of the ecotype
numbers and proportions between sites. The species within the ecotypes that contribute to
similarities or differences are then investigated to determine how differences in their
proportions could have impacted hominins.
Ecomorphological Similarity of the Carnivores
During the Plio-Pleistocene, hominins and carnivores had the potential to interact
while competing for carcasses. Archaeological evidence shows that Plio-Pleistocene
hominins and carnivores overlapped in their resource use, and therefore would have been
competitors (de Heinzelin 1999; Semaw et al. 2003; Dominguez-Rodrigo 2005; Semaw
2000; Potts, 1988, 2003; Bunn and Kroll 1986; Blumenschine 1995; Shipman 1986).
Hominins may have interacted with many different carnivore species in different ways.
While certain carnivores, such as saber-toothed felids, may have produced carcasses that
still contained flesh and marrow (Ewer 1954, Blumenschine 1987, Marean 1989, Arribas
and Palmqvist 1999), other carnivores, such as bone-cracking hyaenids, may have
consumed many of the carcasses on the landscape (Blumenschine 1987, Blumenschine et
al. 1994, Turner 1992). Also, carcass theft after a kill may occur depending on the body
size and grouping behaviors of the species involved (Van Valkenburgh 2001).
The prospects for hominins as hunters or scavengers during the Plio-Pleistocene
would have depended in part on the group of carnivore species present and their
ecological traits, such as body size and feeding adaptations. Feeding adaptations include
morphological specialization for behaviors such as flesh-slicing or bone-cracking. Body
6
size is an important determinant of prey size and competitive interactions (Carbone et al.
1999, Van Valkenburgh 2001).
Feeding adaptations and body size are termed ecomorphological traits because
they are based on morphological measurements that relate to the ecological
characteristics of a species. These ecomorphological measurements can be used to
characterize carnivores from different species according to their behaviors. For instance,
ecomorphological characteristics are used to compare bone-cracking adaptations in
hyenas in East Asia and East Africa, regardless of the taxonomic relationship between the
species. This comparison shows differences in adaptations to bone-cracking and in the
probable amounts of competition from carnivores that hominins would have faced in East
Asia and East Africa. Ecomorphological comparisons are used to determine whether
specific carnivores are avatars. Avatars here are species from different regions that have
similar feeding adaptations and body size (Damuth 1985). Measurements of feeding
adaptations classify carnivores into dietary classes such as highly carnivorous,
omnivorous, or bone-crackers. However, avatars that are similar in diet and in body size
may have been different in other aspects of behavior, such as locomotion, that are not
researched here.
The combination of ecological characteristics in the carnivore guild as a whole in
a particular region and time would have shaped potential interactions with hominins that
used meat and marrow and that may have scavenged from other animals. A guild refers to
all species of a particular group that obtain and use resources in a similar manner (Root
1967). Here, the carnivore guild refers to members of the order Carnivora that are over 1
kg in body mass. Lewis (1995, 1997) hypothesized that there were ecological differences
7
in carnivore locomotion and prey capture behavior between East Africa and South Africa
that would have led to differences in hominin scavenging opportunities. Likewise, large
numbers of bone-cracking species may have consumed many carcasses, making it more
difficult for hominins to scavenge (Blumenschine 1987, Blumenschine et al. 1994, Turner
1992). This shows that the adaptations of the guild as a whole - the numbers of species
with bone-cracking or flesh-slicing adaptations, as well as the numbers of omnivorous or
carnivorous taxa that may have been competitors would have been relevant to a
scavenging or hunting hominins ability to obtain meat and bone marrow. Hominin use of
marrow also occurred outside of Africa; percussion marked bones have been found dating
to 1.66 Ma at Majuangou in the Nihewan Basin (Zhu et al. 2004). If, therefore, hominin
behavioral potential was similar, then the composition of the carnivore guild in East Asia
would have affected the possibilities for hominins living there. Carnivore adaptations
were also important for dispersing hominins. Animal products have constant properties,
unlike plant foods. Edible plants may vary in distribution, especially in the temperate
latitudes of East Asia. In order to obtain those animal products, hominins would have had
to interact with the carnivore guild. In this dissertation, similarities and differences in the
carnivore guilds of East Asia and East Africa are determined in part by the presence of
avatars. Guilds containing many similar avatars probably led to similar niches for
carnivorous hominins because of similar relations between species. Specific differences
between guilds could imply new competitors or sources of potentially scavengeable
carcasses.
The structure of the East Asian carnivore guild is also relevant because hominins
were a new immigrant taxon to East Asia and they were likely using resources formerly
8
exploited only by members of the order Carnivora. Hominins would have been entering
the guild of East Asian carnivores as a type of partially carnivorous mammal that was
unknown and unlike the others present.
Research on dispersal and immigration into new communities in general suggests
that communities that are successfully colonized have suffered recent extinctions
(Vermeij 1991) or are less diverse than other communities that are saturated (Brown
1989, Ricklefs and Schluter 1993, Vermeij 1991). Immigrant taxa rarely cause
replacement by competitive exclusion (Vermeij 1991), but may instead cause enrichment
in the recipient community when an immigrant adds to the species diversity (Flynn et al.
1991, Vermeij 1991). Immigrant taxa may use resources in a different way compared
with the incumbent taxa in order to be successfully integrated into the endemic
community.
The circumstances of hominin colonization of East Asia during the early
Pleistocene with regard to the carnivore guild are investigated here. Older carnivore
guilds from Pliocene faunal assemblages from Longdan, Longgupo and the Haiyan
Formation in the Yushe Basin are compared with the Pleistocene guilds from the other
East Asian sites. Comparisons of the carnivore guild prior to and after hominin arrival
could show whether hominins took advantage of unrepresented roles, such as flesh-
slicing, bone-crushing or group hunting, or whether hominins were likely to have
enriched the carnivore guild, using resources in a different way. Character displacement
in anatomical traits minimizes overlap of resource use and competition among carnivore
guild members (Mooney and Cleland 2001). It may occur after the immigration of a new
species into the guild (Ricklefs and Schluter 1993). However, the possibility of character
9
displacement with regard to the East Asian carnivore guild must be evaluated in terms of
both hominin immigration and general environmental change. Environmental changes
may have resulted in changes in patterns of resource consumption (Sher and Hyatt 1999,
Davis et al. 2000, Shea and Chesson 2002) and provided opportunities for invaders
(Lozon and MacIsaac 1997). Environmental changes in both the Asian and African
regions during the Plio-Pleistocene are discussed in chapter two. The questions asked
about carnivores in this dissertation are as follows:
1) Were there carnivore avatars in East Asia and East Africa? Were the carnivore
guilds as a whole similar, with a similar distribution of ecotypes? What were the
differences in the ecological characteristics of the carnivores in these regions?
2) Were there changes in carnivore ecomorphology between the Pliocene and
Pleistocene of East Asia? Were there changes in the structure of the East Asian
carnivore guild? Prior extinctions without replacement by another carnivore
avatar may have indicated unfilled niches, whereas a lack of change in the
distribution of avatars may indicate enrichment or increased ecological diversity
of the East Asian fauna when hominins arrived. Opportunities for hominins in a
guild with unfilled niches would have differed from those in a saturated guild or
one with increasing ecological diversity.
The ecological characteristics of the fossil carnivores from East Africa and East
Asia are evaluated using ecomorphological measurements of the dentition designed to
sort carnivores into feeding categories including flesh-specialists or hypercarnivores,
10
bone-crackers and omnivores. These measurements show quantifiable similarities and
differences between species. For each ecomorphological index, categories are created for
ecologically different subsets of measurements. These analyses show which species are
avatars, and are used to compare the guilds of East Asia and East Africa, as well as the
East Asian guilds through time.
Organization of the Dissertation
This dissertation is organized into two sections, the first concerned with questions
about the overall ecological similarity of the large mammalian community, and the
second with the comparative ecomorphology of the carnivore guild. Background to the
question of overall mammalian ecological similarity, as well as detailed information
about the sites from which the ancient faunal assemblages are drawn is contained in
chapter two. Chapter three describes the methods used to analyze ecological similarity of
ancient East Asian and East African faunas. The results of these analyses are given in
chapter four. Background to the section on carnivore ecomorphology is in chapter five.
Chapter six describes the methods used to analyze comparative carnivore
ecomorphology, and chapter seven describes the results. Discussion of all results and
general conclusions are presented in chapter eight.
11
Chapter 2: Background to Ecological Similarity Analysis
Hominins are an integral part of the mammalian community (Foley 1987).
Mammalian remains found with hominins have been used to interpret hominin habitat
preferences. The mammalian ecological structure (or community structure), which is
defined as the proportions of mammals that have certain classes of adaptations, is
correlated with environmental conditions, including the amount of vegetation,
precipitation and the temperature range. The types of mammals present in a community
may affect the animal resources available for a hominin, through scavenging or hunting.
The mammal community also reflects the vegetative community, which is also a food
source for hominins. These aspects of habitat and mammalian community structure are
particularly interesting when considering the ecological context of hominin dispersal to
East Asia and how those conditions compare with East Africa.
This chapter discusses the use of mammalian adaptations to make environmental
determinations, with reference to ecological structure methods. The modern comparative
environmental divisions used in the analysis are described. Theoretical expectations for a
dispersing mammal, information about mammalian dispersals from Africa during the
early Pleistocene, and environmental conditions conducive to dispersal are discussed.
Finally, information about the Plio-Pleistocene East African and East Asian research
sites, with emphasis on their environmental conditions, is summarized.
12
Mammals as Environmental Indicators
Mammals in hominin sites have been used to determine the type of environment
in which hominins lived. Functional morphology of single species or groups of species
(such as bovids or carnivores) found with hominins has been used to estimate aspects of
habitat such as vegetation cover (Kappelman 1988, 1997; Lewis 1997; Spencer 1997;
Elton 2001, 2002; Vrba 1974, 1975, 1980). Abundance data for mammals that are
correlated to particular habitat types (such as closed or open) reflect environmental shifts
(Bobe and Eck 2001, Bobe et al. 2002, Bobe and Behrensmeyer 2004).
Ecological structure in the mammalian community is commonly defined as the
proportions of adaptations related to diet, body size, locomotion and substrate use
(Andrews 1996, Reed 1998, Rodrguez 2004). Patterns of ecological structure are based
on physical factors such as climate, vegetation and precipitation, and are correlated with
habitat types (Andrews et al. 1979). Communities from locations with similar physical
conditions converge on a similar structure, even if the sets of species from those
communities are taxonomically different. Community structure methods describe faunas
by the ecological rather than taxonomic composition of the fauna. Higher temperatures
and greater amounts of water lead to greater plant productivity, which in turn increases
the number of herbivores (Ritchie and Olff 1999, Janis et al. 2002) and the number of
species relying upon arboreal substrates. African habitats range from rainforests to
deserts, with differing amounts of moisture and different temperature regimes in each.
Africa has a number of different habitats, in which different ecological structures and
proportions of adaptations are found (Reed 1997, 1998, 2008; Andrews et al. 1979,
Andrews 1996). African forests have similar ecological proportions to tropical forests in
13
Australia, Malaya and Panama (Andrews et al. 1979). Some ecological types are
particularly useful for distinguishing habitat types. Andrews (1996) found that temperate
environments tend to have more terrestrial animals compared with tropical ones. Tropical
and non-seasonal habitats, such as evergreen forests, have more frugivorous, arboreal,
and scansorial species than environments that were drier, such as savannas (Andrews
1996). Mendoza et al. (2005) found that grazers and mixed feeders are more common in
bushland and savannas than in forests or arid environments. Mendoza et al. (2005) also
found that highly carnivorous species (including bone-cracking animals) are more
common in open environments. Within Africa, Reed (2008) found that adaptations such
as arboreality, terrestriality, frugivory, grazing and mixed feeding are most useful in
distinguishing habitats, with arboreality and frugivory signaling more vegetation cover,
or the presence of riverine gallery forests, while other adaptations signify more open
landscapes.
Ecological or community structure methods use different modern environments to
model how the ecological structure changes with habitat. Ecological structure methods
are also used to compare among ancient faunas to determine how they differ. Comparison
of ancient and modern faunas described using ecological structure methods may show
whether ancient faunas are analogous to modern ones. This dissertation compares Plio-
Pleistocene fossil faunas located in East Africa and East Asia. The East Asian fossil
localities occur at higher latitudes compared with the East African comparative sites.
While most seasonal shifts in modern African localities concern the amount of
precipitation, higher latitudes also experience temperature shifts (Reed and Rector 2007).
Construction of an ecological structure system to compare localities from distant
14
geographic locations, as well as from tropical and temperate habitats, requires the use of
relatively broad environmental categories (Mendoza et al. 2005). Here, a set of fauna
from modern African and Eurasian localities is classified into environmental categories
using Baileys ecoregions (Bailey 1998), which are described in more detail below.
Biogeography and Ecological Structure:
Though ecological structures are similar in different locations under similar
ecological conditions, historical factors affect the distribution of species and the
proportions of ecological types, producing geographic differences in structure. For
instance, Andrews (1996) found geographic effects in an ecological analysis of modern
tropical evergreen forests, temperate forests, savanna woodlands, steppe, and tundra
habitats. While the tropical forests were separated from the other environments,
geographic substructure was evident in the separation between African and Asian tropical
forests. Likewise, temperate deciduous forests in Eurasia and North America had
different structures, possibly resulting from different environmental conditions
unaccounted for in the study, different histories and different regional species pools.
An ecological structure study of modern localities in Eurasia and North America
looked at the relative roles of convergence in mammalian communities from similar
environments compared with the influence of geographic location (Rodrguez et al.
2006). Both biogeography and environmental variation played a role in the positioning
these faunas in multivariate space (Rodrguez et al. 2006). Arid communities, such as
deserts and steppes, were particularly convergent, perhaps because there are few ways to
structure such a community with the limited available resources (Rodrguez et al. 2006).
15
There were significant differences between New World (Nearctic) and Old World
(Palearctic) faunal communities overall, which relate to differences in the composition of
the species pools in these regions.
Another analysis compared the ecological structure of mammalian communities
grouped by vegetation type in African and Asia to generate a predictive model (Mendoza
et al. 2005). The discriminant function analysis grouped broadly similar vegetational
communities from the two continents together showing that ecological structure can
identify environmental convergence (Mendoza et al. 2005). However, some vegetation
types are only found in Africa or Asia, meaning that some communities could not be
compared (Mendoza et al. 2005). Evergreen forest, bushland and arid communities,
which are found in both Africa and Asia, are similar in structure. Asian deciduous forests,
which also contain grass areas, are similar to African wooded savannas. By grouping the
habitats into relatively broad categories when comparing distant geographic localities, it
is possible to see the general features of ecological structure (Mendoza et al. 2005).
Ancient Communities without Modern Analogs:
Some aspects of past ecosystems (or past ecosystems as a whole) may not have a
modern analog, a phenomenon called historical non-equivalence. When analyzing the
fauna of Makapansgat, Reed (1998) found that proportions of some extant taxonomic and
ecological groups were very different compared with modern sites. Andrews et al. (1979)
also noted some localities seemed to have a distribution of ecological types that is not
represented in current African settings. In other cases, such as an Olduvai fauna from the
middle of Bed I, ecological information from faunas does not match current habits of
16
close relatives, leading to an interpretation of greater structural complexity in that ancient
habitat compared with the modern location (Soligo and Andrews 2004). Andrews (1996)
recommended comparing ecological variables individually to determine the
characteristics of ancient habitats that do not correspond to modern categories.
Environmental Profiles of Modern Comparative Sites:
Baileys ecoregions were used to classify modern localities. This is a hierarchical
system in which the world is divided into domains and those domains are each divided
into divisions. Each division may be either lowland or mountainous. Temperature and
moisture patterns divide the world into tropical humid, humid temperate, polar and dry
domains (Bailey 1998). Within these domains, latitude, precipitation, continental
position, altitude and seasonality produce vegetation patterns that are described in the
divisions. Each division has a typical series of altitudinal vegetational zones that occur
when that division contains areas of mountainous terrain. Descriptions below are based
on characteristics described in Bailey (1998) unless otherwise noted.
Dry Domain:
Temperate Deserts:
Temperate deserts are found in the interior of the Eurasian continent. They
receive very little precipitation and have hot summer temperatures and very cold winter
temperatures. The lack of water and extreme temperature range limits vegetation to
woody shrubs. As altitude increases, the vegetation changes first to semi-desert woodland
and then to meadow.
17
Temperate Steppe:
Temperate steppes typically feature grasslands with scattered scrubland and trees.
Most fauna are grazers. Winters are cold and dry, while summers are hot or warm with
rainfall. If rainfall decreases, temperate steppes may become deserts. The altitudinal
sequence from lower lands to higher ground for temperate steppe is: steppe, coniferous
forest, tundra or in other areas, steppe, mixed forest and meadow.
Tropical-Subtropical Steppe:
Tropical-subtropical steppes are arid and hot. Precipitation occurs irregularly from
year to year. The vegetation consists mainly of grass, but may include shrubs or trees.
This division may also be described as an acacia-grassland savanna. Tropical-subtropical
Steppe Mountains include a gradient that runs from steppe or semi-desert to mixed or
coniferous forest to alpine meadow or steppe.
Tropical-Subtropical Desert:
These deserts are extremely arid with large variations in temperature between day
and night. Very sparse vegetation includes shrubs, cacti and grass. Tropical-subtropical
deserts include the Sahara, the Arabian Peninsula and the Thar. The altitudinal sequence
is from lower to higher altitudes is semi-desert, shrub, open woodland and finally steppe
or meadow.
Humid Temperate Domain:
Prairie:
Although the precipitation in prairies is sufficient to support grassland, it does not
support trees unless the prairie is close to a wetter division. In that case, mosaics of
18
deciduous forest and grassland may occur. Mountains cause the following zones: forest-
steppe, coniferous forest and meadow.
Subtropical:
The subtropical division is characterized by a climate without a dry season.
Streams contain water for most of the year. The average annual rainfall for subtropical
forests of the broadleaf schlerophyllous type is 1283.7mm (Wang 1961). Precipitation is
increased during the summer. The average temperature for Chinese subtropical forests is
15.9C (Wang 1961). Subtropical divisions typically contain forests with evergreens such
as oak, laurel and magnolia. The forest floor is thickly vegetated with bamboo, shrubs
and herbs. At northern borders, subtropical forests may also have deciduous broadleaf
trees. The subtropical mountainous zones range from mixed forests to meadows.
Hot Continental:
Hot continental vegetation includes tall broadleaf deciduous trees, with a seasonal
herb layer on the ground. This is the native division type for areas in northern China and
was originally found between 20 and 50N latitude (Ching 1991). Currently, it is not well
represented in China because of the large human population (Ching 1991). The hot
continental division has hot summers and cool winters, without a dry season. A
mountainous area will have deciduous or mixed forest, coniferous forest and finally
meadows.
Humid Tropical Domain:
Savanna:
Savannas are a very variable type of division, with different subtypes of
vegetation. These vegetation types include scrub woodlands (with a discontinuous
19
canopy layer) and woodland savanna, in which grassland, trees and shrubs are
interspersed. Savannas are found in Africa, as well as in India and Southeast Asia.
However, the human population in the Asian areas is large and has altered the vegetation
and the faunas substantially (Cole 1986). Cole (1986) notes that dry deciduous
woodlands in India and Burma are similar to savanna woodlands in Africa. In Southeast
Asia, deciduous forests are found in areas with 1000-2000 mm of rain and a four to seven
month dry season (Cole 1986). These Southeast Asian savannas include discontinuous
canopied woodlands interspersed with denser areas of deciduous or rainforest (Cole
1986). Blasco (1983) describes this type of vegetation as an open forest with grass
covering the ground. Savannas have wet and dry seasons. Streams dry out in the dry
season or flood surrounding grasslands during rainy seasons. Mountainous savannas
include open woodlands, deciduous forest, coniferous forest and then a steppe or
meadow.
Rainforest:
Rainforests include many species of trees able to thrive in a setting with high
temperatures and abundant rainfall. A subtype of rainforest (tropical deciduous) occurs in
areas that have a dry season. Tropical rainforest has a continuous canopy layer of
broadleaf trees. The fauna is especially rich and includes many arboreal species.
Mountainous rainforests shift from evergreen forest to meadows.
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Dispersal and Biogeography:
Theoretical Expectations for Dispersal:
The dispersal of hominins into East Asia can be considered in light of
biogeographic theoretical expectations. According to Vermeijs (1991) study of historical
biotic exchanges, in which species from one geographic locality colonize another
location, very few species actually disperse when a geographic exchange opportunity
occurs. A new colonizing species may have a competitive advantage over species in the
recipient biota, especially with regard to disease or pathogen resistance (Vermeij 1991).
The study also reveals that biotic exchange often occurs primarily in one direction,
leading to speculation that one ecological community is competitively superior over the
other. A mediating factor in exchange asymmetry is the presence of suitable habitats for
immigrant species (Ricklefs and Schluter 1993). Similarity in physical aspects of the
environment is important to successful colonization (Brown 1989). Environmental and
physical similarity is likely to result in similar food resources and similar types of species
in the communities (Brown 1989). However, many species are able to tolerate a range of
environmental conditions when there are few predator and competitor species (Brown
1989). Prior extinctions may increase a communitys vulnerability to colonization
(Vermeij 1991). Brown (1989) also noted that less diverse communities are more likely
to be colonized. In particular, a deficit of predators could be an important factor.
Conversely, a stable community that has not suffered extinctions could be said to be
saturated (Ricklefs and Schluter 1993, Vermeij 1991) and thus less susceptible to
invasion. If a saturated community were invaded, the process of competitive exclusion
21
would cause extinctions among the incumbent species. However, Vermeij (1991) found
that colonizing species rarely caused extinctions. Instead of replacement, dispersers find a
place within the new community in a process of enrichment (Flynn et al. 1991, Vermeij
1991), perhaps because the disperser is exploiting available resources in a new way
(Ricklefs and Schluter 1993). Brown (1989) also found that dispersing species succeed in
colonization more often when they can occupy new niches compared with the native
species.
Community Structure:
The composition of local communities is determined by climate, habitat and local
landscape (Ricklefs and Schluter 1993), as well as by competitive and predatory
interactions between species (Morin 1999). Local community structure and composition
may also be influenced by the sequence in which organisms colonize the location
(Robinson and Dickinson 1987, Robinson and Edgemon 1988, Drake 1991, Drake et al.
1993, Wilson 1992). Above the local populations are metapopulations, which are local
populations in a region linked by dispersal of species between them (Morin 1999).
Species from the regional metapopulation may replace species that become extinct in the
local populations depending on their dispersal ability and their habitat and landscape
preference (Morin 1999). The regional species pool is an important factor in maintaining
local diversity (Brown and Gibson 1983). Community structure at a local level is greatly
influenced by the composition of the regional species pool (Mooney 1977, Schluter 1986,
Ricklefs 1987, 1989, Lawton 1984, Cornell and Lawton 1992, Ricklefs and Schluter
1993, Brown 1995). The species present at the regional level are determined by
differences in environments as well as different interspecific interactions (Paine 1966,
22
1974, Lubchenco 1978, 1980, Menge 1995). Presence or absence of certain individual
species may also cause differences in regional species pools (Tonn and Magnuson 1984,
Rahel 1984, McPeek 1990, Werner and McPeek 1994). Species in the regional species
pool may be supplied by diversification within clades (Webb et al. 2002), or by dispersal
due to linkages with other regional species sets (Ricklefs and Schluter 1993).
Diversification processes may result from adaptive radiation (Rosenzweig 1978, 1995,
Pimm 1979, Feder et al. 1988, 1990, Schluter and McPhail 1992, Schluter 1993, Rice and
Hostert 1993, Schluter and Nagel 1995, Losos et al. 1998, McPeek and Brown 2000),
sexual selection (Lande 1981, 1982, Lande and Kirkpatrick 1988, West-Eberhard 1983,
Kaneshiro 1983, 1988, 1989, Seger 1985, Kaneshiro and Boake 1987, Turner and
Burrows 1995, Seehausen et al. 1997, Payne and Krakhauer 1997), the evolution of
specific mate recognition systems (Paterson 1978, 1993), or chromosomal
rearrangements (King 1993).
Each species has a fundamental niche of conditions in which it can survive as a
viable population (Hutchinson 1957). One of the aspects of the niche is the species
geographic range. In phylogenetic niche conservatism, the ancestral niche characteristics
of a species are conserved in its descendants, leading to similarities in environmental
tolerance and failure to expand into adjacent but environmentally different territory
(Weins 2004, Peterson et al. 1999, Ricklefs and Latham 1992, Ackerly 2003, Weins and
Donoghue 2004). Niche evolution, either in expansion of environmental tolerance or a
shift to a new environmental specialization, would enable a species to colonize new
habitats (Weins and Donoghue 2004).
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The role of neutral processes in community assembly is debated. In his neutral
theory of biodiversity and biogeography, Hubbell (2001) asserts that ecological
communities of trophically similar sympatric species are structured by chance, historical
factors and random dispersal of individuals. These communities are open to immigration
and are not at equilibrium (Hubbell 2001). This neutral view contrasts with a niche
assembly theory in which members of the community interact strongly with each other,
competition plays a strong role and the composition of the community may be deduced
from functional roles of the species (MacArthur 1970, Diamond 1975). The relative
importance of random or neutral processes compared with interactions between species
and between species and their environments has also been investigated (Kembel and
Hubbell 2006, Kelly et al. 2008, Jabot and Chave 2009).
Dispersal of African Mammals:
Plio-Pleistocene African mammals are found in Asia at the Levantine site of
Ubeidiya, dated to approximately 1.6 and 1.2 Ma (Belmaker 2005). Although the fauna
includes a mix of species from different realms, such as the oriental, most elements were
from the Palearctic (Tchernov 1992b). The sub-Saharan species identified from that
period are Pelorovis oldowayensis, Oryx cf. gazella, Kolpochoerus oldovaiensis, Equus
tabeti, Theropithecus cf. oswaldi, Hippopotamus gorgops, Mellivora sp., Herpestes sp.,
Megantereon sp. and Crocuta sp. (Belmaker 2005). However, many of the lineages with
African affinity were derived from in situ evolution of previously dispersed lineages
(Tchernov 1992a, b). Other genera, such as Crocuta and Megantereon, have been found
in Pliocene Asian sites and may not have been recent immigrants or may not have been
24
African-derived. The earlier Pliocene site of Bethlehem shows many open country
mammals in an environment interpreted as similar to an African savanna (Tchernov
1992a, b, Turner 1999). Martnez-Navarro (2004) suggested that the presence of
Pelorovis at Ubeidiya implied the extension of savannas, while Kolpochoerus indicated
the occurrence of gallery forests. Belmaker (2005), however, found that African-derived
species were not particularly abundant at Ubeidiya and instead reconstructed the site as
similar to Mediterranean environments. Most of the African species found at Ubeidiya
did not disperse further into East Asia. The exceptions are Theropithecus oswaldi, which
is found in Europe and India, and Homo (Martnez-Navarro 2004).
Environment and Dispersal:
Environmental and geographic changes may have presented opportunities for
hominins to expand into Eurasia, by the opening of physical pathways or by the spread or
existence of environments in which hominins were able to survive. Environmental
factors, including seasonal climate, temperature range, and ecological factors, such as
food availability, would have played a role in determining whether hominins were able to
survive in new dispersal sites for the long term.
Dennell (2004) tied hominin dispersal to the presence of grassland habitats.
According to climatic reconstructions, grasslands were present in Asia at 3 Ma (Dowsett
et al. 1999). Based on information that places East Asia in tropical and subtropical
environments and describes Indonesian settings as savanna or open woodland, Dennell
(2004) concluded that hominins would have been able to disperse across Asia because of
the similarity in environments, specifically the presence of savanna-like settings across
25
Asia. Vegetational and faunal contrasts between different latitudes were not as strong
during the late Pliocene and early Pleistocene as they are today, especially since modern
desert barriers were not yet fully formed (Dennell 2004). The appearance of savannas and
woodlands in Asia and Africa may have been tied to potential times of dispersal, which
means that dispersal prior to the early Pleistocene is possible (Dennell and Roebroeks
2005).
East Africa
Evidence of Hominins and Dates:
East African sites have long been a source of hominin fossils, as well as those of
other mammals and have provided information about hominin anatomy, culture and
habitat. Faunas from the well-known sites in Koobi Fora, West Turkana and Olduvai
Gorge are used here to compare to the East Asian Plio-Pleistocene sites. Turkana Basin
faunas were analyzed by stratigraphic members. At Koobi Fora, these members included
the Upper Burgi, KBS, Okote and Chari. The Chari member has a very sparse fauna
(Turner et al. 1999). At West Turkana, the members Lokalalei, Kalachoro, Kaitio, Natoo,
and Nachukui were included. Olduvai Beds I and II were also analyzed. The East
Turkana sites date from 2.68 to 0.74 (1.39 if the Chari is excluded) (Feibel et al. 1989,
Brown et al. 1985). The West Turkana members date from 2.52 to 0.7 Ma (Feibel et al.
1989, Brown et al. 1985). These sites were dated by correlation with tuffs dated by K/Ar
dating. Olduvai Bed I dates to 2.03 Ma to 1.78 and Bed II from 1.78 to 1.33 Ma (Walter
et al. 1991, 1992, Tamrat et al. 1995).
26
Environmental History of the Turkana Basin:
Environmental evidence as a whole shows increasing aridity and variability in
East Africa after 3 Ma (deMenocal 2004). Trauth et al. (2005) found evidence of deep
lakes in the periods of 2.7 to 2.5 Ma, 1.9 to 1.7 Ma and 1.1 to 0.9 Ma in East Africa,
leading them to conclude that those were relatively humid periods within the overall
trend toward aridification. However, those periods were highly variable in climate, with
both arid and humid intervals (Owen et al. 2008). A series of temporary lakes formed in
the Turkana Basin beginning at 2.0 Ma, but lacustrine facies disappeared after 1.7 Ma
(Feibel et al. 1991, Feibel 1997). Also, river channels of the Omo dried up between 1.7
Ma and 1.4 Ma (Brown and Feibel 1991).
Pedogenic carbonates show a transition between woodland to more open savanna
between 3 and 1 Ma at the Turkana Basin and Olduvai Gorge (Cerling 1992, Cerling et
al. 1988). More arid-adapted mammalian taxa appear between 2.5 and 1.8 Ma
(Behrensmeyer et al. 1997). Based on pollen data, Bonnefille (1995) found that the
Lower Burgi had vegetation, first signaling relative cold, and then dry climate. During the
time of the upper Burgi and through the Okote, climate fluctuated between humid and
arid conditions. Pedogenic carbonates sampled at Koobi Fora indicated a trend of change
from closed woodlands to open woodlands or shrublands between 2 and 1.75 Ma (Quinn
et al. 2007). Between 1.75 and 1.5 Ma, different types of low shrubland environments
were found, which Quinn et al. (2007) interpreted as fragmentation of woodland habitats.
After 2.0 Ma, the Turkana Basin experienced a period of faunal turnover and
grassland expansions (Bobe and Behrensmeyer 2004). Many grassland mammal species
have first appearances during the interval of 2.0 to 1.8 Ma, including hypsodont bovids
27
and suids, while the species that went extinct included forest and closed habitat dwellers
(Bobe and Behrensmeyer 2004). Omo mammals associated with forest habitats decreased
in abundance after 3.2 Ma, while secondary grassland taxa became more abundant after
2.5 Ma (Bobe et al. 2002).
Reeds (1997) ecological analysis of the Upper Burgi, KBS and Okote faunas
shows environmental changes. Whereas the Burgi fauna was interpreted as a mixture of
open woodland, edaphic grasslands and riparian woodland, with frugivores/folivores,
fresh grass grazers and terrestrial/arboreal animals, the KBS had fewer arboreal taxa and
a greater proportion of grazers (Reed 1997). The KBS was interpreted as scrub woodland
or arid shrubland with grasslands. The Okote was described as edaphic grasslands, having
many grazers, but also contained arboreal animals from gallery forests (Reed 1997).
Overall, hominins in the Turkana Basin lived in different habitat types while the climate
fluctuated, but tended towards aridification.
Environments in Olduvai Gorge:
A broad and shallow lake was present during the deposition of Bed I (Hay 1976).
Faunal analyses have been used to show what types of environment were present. Butler
and Greenwood (1973) and Gentry and Gentry (1978a,b) found conditions that signaled
increased aridity at the top of Bed I. Analyses based on bovid ecomorphology found that
closed or intermediate habitats prevailed (Kappelman 1984, Plummer and Bishop 1994).
Pedogenic carbonates sampled from an interval of 1.845 to 1.785 Ma showed variation in
climatic conditions and fluctuation between woodlands with open canopies and grass, and
wooded grasslands (Sikes and Ashley 2007). The amount of C4 grassland varied between
40-60% (Sikes and Ashley 2007). Using an ecological structure analysis, Andrews et al.
28
(1979) concluded that Olduvai Bed I had a similar fauna to that of the Serengeti and to
woodland-bushland communities. During the deposition of Bed II, the lake was reduced
in size and the area was aridified (Hay 1976). Based on pedogenic carbonates, Sikes
(1994) found that lower Bed II supported a riparian forest, with grassy woodland further
away. Kappelman (1997) found that bovid ecomorphology supported a range of cover
from open to heavy cover, though there were no forest species. Carnivores and hominins
have been primary accumulators for some of the assemblages in Beds I and II
(Dominguez-Rodrigo et al. 2007a, b, Egeland 2007, Egeland and Dominguez-Rodrigo
2008, Leakey 1971, Potts, 1988, Monahan 1996, Blumenschine and Masao 1991).
East Asia
Environments in East Asia:
Environments in East Asia most likely played an important role in facilitating or
impeding hominin dispersal and in determining whether occupation was long-term or
short-term. Evidence from East Asia, including 18O from deep sea cores and loess
deposition analysis, indicates climate change during the Plio-Pleistocene. The 18O
record from deep sea cores records increases in ice volume after the late Pliocene
(Shackleton et al. 1985; Shackleton et al. 1990, Shackleton et al. 1995). The northern
hemisphere ice sheet increased during the intervals of 3.6 to 2.7 Ma, 2.7 to 2.1 Ma and
1.5 to 0.25 Ma (Tian et al. 2002).
Loess, carried by the winter monsoon from the northwest of China, reflects
aridification of central Asia (Liu 1985). The formation of deserts in north and northwest
China is linked to the uplift of the Tibetan plateau, which blocks moisture from the Indian
29
Ocean (Guo et al. 2002). Loess particles deposited at specific sites are coarser during
glacial intervals due to southward migration of deserts and to increased wind intensity
(Ding et al. 2005). The summer monsoon is responsible for approximately 80% of the
moisture in the loess-desert margin area, with the desert margin moving north as the
summer monsoon strengthens and moves north (Ding et al. 2005). Changes in the sizes of
loess particles indicates that the desert margin moved south at 2.6, 1.2, 0.7 and 0.2 Ma,
corresponding decreased strength of the summer monsoon and ultimately attributable to
glaciation (Ding et al. 2005).
The mineral record provides another proxy suggesting aridification. The mineral
hematite is formed by chemical weathering. The production of hematite is decreased
during glacial periods so that the content of hematite, measured by remnant
magnetization, reflects the degree of chemical weathering and the degree of aridification.
The patterns coincide with the 18O record to suggest aridification and cooling
throughout the Quaternary during both glacial and interglacial periods (Deng et al. 2006).
Despite the overall trends of aridification and cooling, considerable environmental
fluctuation probably occurred at specific sites. The pollen record from a location on the
Chinese Loess Plateau at 357 N and 10712 E shows changes in vegetation,
temperature and the moisture regime in that area (Wu et al. 2007). Between 3 and 2.6 Ma,
arboreal pollen was dominant, in a climate that was mostly warm and humid. This
interval was followed by a drier and cooler period from 2.6 to 1.85 Ma, which featured
arid adapted plants and fewer trees. The location sampled was reconstructed as having
trees on the hills and grass-filled valleys. During the 1.85 to 1.5 Ma interval, Pinus, as
well as firs and spruce trees are dominant, leading to an interpretation of a forest-steppe
30
with a cool and humid climate. In the next time interval (1.5 to 0.95 Ma), Pinus remains
very common, but broadleaved trees and plants thriving in temperate environments are
present, showing a warm-temperate and humid climate. The species of Pinus present is
believed to be one restricted to warm, temperate environments with more than 400 mm of
rain annually. Subsequent samples, from the interval 0.95 to 0.5 Ma, show a decrease in
tree pollen and an increase in herbs and shrubs, suggesting an open steppe with
grasslands.
Other lines of evidence suggest climatic changes in areas east of the loess plateau
in China. Using data from soil, loess, pollen and the biogeographic distribution of apes
and cercopithecids, Jablonski et al. (2000) reconstructed most of southern China as a
tropical environment suitable for pongids and hylobatids during the late Pliocene and
early Pleistocene, while parts of northern China were thought to have had a more
subtropical climate.
East Asian Focus Sites: Environment, Fauna, and Dating
Chronology of East Asian Sites:
The East Asian sites are dated by a combination of paleomagnetic stratigraphy
and biochronological inferences and comparisons with better dated localities. The
Nihewan sensu stricto is a typical fauna. Many other faunas in East Asia, particularly in
North China, have been compared with it in order to assess similarity in terms of how
many species are shared and thus to infer whether the fauna comes from approximately
the same time period as the classic Nihewan fauna. Past studies have also looked at the
proportion of extinct taxa as a means of judging relative age (e.g., Han and Xu 1985).
31
Recent work has produced land mammal ages for China typified by combinations of taxa,
and correlations with European mammalian biozones (Li et al. 1984, Tedford 1995, Tong
et al. 1995, Qiu and Qiu 1995, Deng 2006). Studies in the Yushe Basin (Tedford et al.
1991, Flynn et al. 1991, 1997), at Lantian (Zhang et al. 2002) and Lingtai (Zheng and
Zhang 2001) have served to better integrate mammalian biochronology with the
paleomagnetic timescale.
Nihewan Basin:
The Nihewan Basin has produced some of the earliest evidence of hominin
presence in China. It is also known as a source of mammalian fossils, which with
environmental data, produces important evidence about the ecological context of
hominins in East Asia. The Nihewan Basin sites examined here include the
archaeological sites of Majuangou, Donggutuo and Xiaochangliang, as well as the non-
hominin fauna known as the Nihewan sensu stricto or the Xiashagou fauna. The Nihewan
basin contains fluvial, lacustrine and eolian sediments (Zhu et al. 2003, Deng et al. 2008).
Xiaochangliang:
The Xiaochangliang site, located in the Nihewan Basin at 40.2N, 114.65E,
contains artifacts and a fossil fauna (Figure 2.1). The artifact layer, which includes many
small flakes, is dated by magnetostratigraphic correlation to 1.36 Ma (Zhu et al. 2001,
2003). The fauna reported by Tang et al. (1995) included typical Nihewan taxa and
corresponded to an early Pleistocene age. Most remains are highly fragmented (Peterson
et al. 2003). From a sample of bones, Peterson et al. (2003) found that although 8.1% had
carnivore toothmarks, this percentage was too small for the fauna to have been
accumulated primarily by carnivores. Shen and Chen (1999) also found carnivore,
32
possibly hyena, modifications on the bones. The assemblage was most likely
hydraulically transported (Peterson et al. 2003, Shen and Chen 2003). The assemblage is
associated with a conglomerate.
Donggutuo:
The Donggutuo site is located at 402 N and 114.67 E. It contains lakeshore
sediments. Schick et al. (1991) report cores and flakes. The site was dated to
approximately 1.1 Ma using paleomagnetic stratigraphy (Li and Wang 1982). This was
confirmed by Schick and Dong (1993), Li et al. (2002), Wang et al. (2005) and Zhu et al.
(2003). The fauna is listed in Wei (1985, 1991), and in Deng et al. (2008).
Majuangou:
Majuangou is located at 4013.517 N and 11439.844 E in the Nihewan Basin.
The four artifact layers contain cores and flakes (Zhu et al. 2004). Paleomagnetic
stratigraphy was used to determine the following dates for the artifact layers: 1.32, 1.55,
1.64 and 1.66 Ma (Zhu et al. 2004). Fossil bones show percussion marks, indicative of
processing for marrow (Zhu et al. 2004). Biochronologically, the fauna is typical of the
Plio-Pleistocene and is similar to that of Xiaochangliang (Tang et al. 1995). Sediments
show that the artifact layers were deposited in wetlands or in lake margins. Pollen data
indicates considerable variation in vegetation over time at the time (Zhu and Potts, pers.
comm.)
Xiashagou or Nihewan sensu stricto:
The Nihewan fauna contains many mammal species and has come to be
considered a standard north China fauna for the late Pliocene and early Pleistocene
(Lucas 2001). However, the fauna does not include any hominin specimens. This fauna
33
was documented by Teilhard de Chardin and Piveteau (1930) and further studied by Qiu
(2000). Deng et al. (2008) estimated the age of the Nihewan faunas to be between the
onset of the Olduvai normal and the Brunhes-Matuyama boundary. Biochronological
studies show that the fauna corresponds taxonomically to the Olivola fauna at about 1.8
Ma (Qiu 2000). About 20% of the mammals are from the Tertiary (Lucas 2001). Many of
the species are forest browsers (Lucas 2001).
Gongwangling, Lantian:
Gongwangling is located at 3412 N and 10928 E. A Homo erectus cranium
was found at Gongwangling. The fossil was found in the L15 Loess Layer, which An and
Ho (1989) dated to 1.15 Ma using magnetostratigraphy. Heslop et al. (2000) estimated
the age of the L15 loess at 1.22 to 1.19 Ma. The complete fauna was described by Hu and
Qi (1978). An environmental analysis of Gongwangling based on the fauna concluded
that this site experienced relatively warm and moist conditions (Dong et al. 2000). The
presence of forests was inferred based on a large number of forest-dwelling taxa (Dong et
al. 2000). Gongwangling is located on the northern edge of the Qingling Mountains,
which divide north and south China, and its fauna includes a number of typically
southern Chinese forest mammals (Hu and Qi 1978). These southern taxa may indicate a
warm period in which certain mammals were able to spread further north. Wang et al.
(1997) described the environment as a cold or cool dry winter with a warm, semi-humid
summer based on stable isotope ratios from the last glacial-interglacial cycle.
Yuanmou:
Yuanmou is located in south China at 2540 N and 10154 E. The Yuanmou
incisors and artifacts, found in a layer dated to ~ 1.7 Ma using magnetostratigraphy and
34
the sedimentation rate, are the earliest evidence for hominins in continental East Asia
(Zhu et al. 2008). The incisor morphology has affinities with Homo erectus and Homo
habilis (Zhu et al. 2008). The fauna contains some Pliocene survivor species, while other
species are typical of the early Pleistocene (Qian and Zhou 1991). Pollen showed the
presence of pine and other tree species, as well as herbaceous vegetation, indicating a
cool and temperate environment (Qian and Zhou 1991, Zhu et al. 2008). While many
grazing species are found in the fauna, taxa associated with other habitats, such as
bushland and forests, also occur (Qian and Zhou 1991).
Longgupo or Wushan
Longgupo is a cave site located in South China at 30.4N, 109.1E. It was
formerly thought to be a hominin site (Huang and Fang 1991, Huang et al. 1995) but
those remains are now thought to represent an ape (Wu 2000). Rocks with crude,
sometimes overlapping facets were also found and considered to be stone tools by the
excavation team (Huang and Fang 1991, Huang et al. 1995). The fauna from this site is
used here as a non-hominin comparator site. Huang et al. (1995) estimated that the site
dates to 1.9-1.8 Ma. Biochronological analyses of the fauna based on the co-occurrence
of species showed that the site has to be Late Pliocene to early Pleistocene (Huang et al.
1995). Electron spin resonance was used to assign the ape level to the Olduvai subchron
(Huang et al. 1995). Many species in the ape zone have also been found at
Gigantopithecus Cave (Huang and Fang 1991). However, mammals from north China, as
well as the local area, are also present in the assemblage, indicating a mixture of species.
From the overall inferred habitat preferences of the species, Huang and Fang (1991)
inferred the presence of forests and a relatively moist climate. However, climate
35
fluctuations may have caused grasslands to develop during some phases. Pollen indicates
climate change during the period when the middle hominoid zone was deposited. There
was a transition from a cold and dry period with herbaceous vegetation, to a climate that
was warm and wet, with forests of evergreen trees (Huang and Fang 1991).
Mohui Cave:
Mohui Cave, located at 233454 N and 1070008 E, is part of the Bubing
Basin, adjacent to the Bose Basin, South China. This cave is the uppermost in a sequence
of caves. The caves were formed when groundwater dissolved limestone. As the
groundwater sank to lower levels, new caves were formed, leaving the oldest caves in the
uppermost position. Flowstones from one of the younger caves were dated by U-series
analysis yielding a formation date of 350-200 ka (Wang et al. 2007). Many of the bones
were gnawed by rodents or carnivores (Wang et al. 2007). Some species typical of the
late Pliocene and early Pleistocene, Ailuropoda microta and Hesperotherium, are present
in the assemblage and supported an early age assignment. The fauna is also similar in
taxonomic composition to Longgupo and Gigantopithecus Cave (Wang et al. 2007),
which are also dated to the late Pliocene or early Pleistocene. The ecological assessment
of the fauna was aided by stable isotope analysis of some of the teeth. Results showed a
closed, forest habitat (Wang et al. 2007).
Jianshi or Longgudong:
Jianshi is a multi-layered cave site located at 303914.9 N, 1100429.1E.
Paleomagnetic information was used to date the site. The younger layers were reported to
be from the Olduvai subchron, while older layers (including a potential hominin) were
dated to greater than 2.15 Ma. The potential hominin teeth found during recent
36
excavations included an upper third molar, a lower first molar and an upper third
premolar. Other teeth attributed to hominins have been obtained earlier. Zheng (2004)
concluded after metrical comparison that the specimens are similar to Meganthropus,
Australopithecus or Pithecanthropus (based on specimens now sunk into Homo).
However, the teeth may represent a species of non-hominin hominoid (Schwartz et al.
1995, Ciochon 2009). Most micromammalian genera come from a geographic class
labeled as the middle subtropical forest type (Zheng et al. 2004). Environmental
classifications of large mammals based on extant relatives show that many came from
forested tropical or subtropical environments (Zheng et al. 2004). Pollen records showed
climate differences for different layers, although the site overall is dominated by conifers
from mountainous areas and by broadleaf trees (Zheng et al. 2004).
Linyi:
Linyi is a non-hominin site in Shanxi, located at 3612 N and 11030 E. The
fauna was found in sands that underlie loessic beds in a lacustrine-alluvial deposit (Tang
et al. 1983). Many of the mammalian species found at this site are typical of northern
China, with the same genera or species being found at the Nihewan Basin or at Xihoudu
(Tang et al. 1983). Due to that faunal resemblance and the fact that the fauna contains
archaic and extinct species, it is thought to date to the Middle or Late Villafranchian
period (Tang et al. 1983). Many of the species (such as Equus, Paracamelus, Gazella,
and Coelodonta) are typical of steppe faunas and are thought to have come from a
grassland environment.
37
Longdan:
Longdan is located at 35 N and 103 E. The Longdan fauna is dated to between
2.55 and 2.16 Ma by paleomagnetic stratigraphy (Qiu et al. 2004). Based on evidence
from faunal resemblance, Qiu et al. (2004) concluded that the fauna was similar to that of
the late Pliocene site St. Vallier, France and dated to about 2.2 Ma. It is definitely older
than that of the Nihewan Basin, since Longdan contains some primitive species or
primitive forms of species (Qiu et al. 2004). Specimens from this site were obtained from
private collections, so detailed information about provenance is unavailable. Collection
bias may have resulted in the composition of this assemblage including many species of
carnivores. Qiu et al. (2004) also noted a taphonomic bias against small animals. There is
evidence that Longdan included steppe or open environments, as well as forested areas.
Climate change may have led to changes in the local habitat. Coelodonta nihowanensis
and Hipparion sinense specimens were both relatively hypsodont; six of the other
herbivores were hypsodont, leading Qiu et al. (2004) to infer the presence of steppe or
open habitats. Six herbivore species were thought to have either lived in forested
environments or to have been browsers or frugivores, supporting the inference of the
presence of bushland, shrubland or forest habitats (Qiu et al. 2004).
Haiyan Formation, Yushe Basin:
The Haiyan Formation is located in the Yushe Basin in North China, at 375 N
and 11259 E. The sediments have been dated to the late Pliocene (Flynn at al. 1991).
Based on magnetostratigraphy, the Haiyan Formation corresponds to the lower
Matuyama reverse chron, and was deposited prior to the Olduvai event, with dates
between 2.5 and 1.9 Ma (Flynn et al. 1991). Biochronological correlation also supports
38
this age (Qiu 1990). Micromammal faunas show considerable turnover between the
preceding Mazegou Formation and the Haiyan, which has 11 first appearances (Flynn et
al. 1991). Turnover also occurred at that boundary among the large mammals (Flynn et
al. 1991). Seven large mammal species also made last appearances in the Haiyan
Formation (Flynn et al. 1991). This fauna is unpublished and information about it is
limited.
Figure 2.1 Map of the East Asian fossil localities. The Nihewan includes the sites of
Xiaochangliang, Donggutuo and Majuangou, as well as the Nihewan
39
Map of the East Asian fossil localities. The Nihewan includes the sites of
Xiaochangliang, Donggutuo and Majuangou, as well as the Nihewan sensu stricto
Jianshi
0 700 km
Map of the East Asian fossil localities. The Nihewan includes the sites of
sensu stricto fauna.
40
Summary:
This chapter introduces ecological structure methods, which describe mammalian
communities using proportions of species with adaptations relating to diet, body size and
substrate. Differences in ecological structure correlate to differences in climate and
environment. However, ecological structure is also affected by biogeographic and
historical processes, especially as these processes affect the composition of the regional
species pool, from which species found in specific assemblages are drawn. In order to
show how ecological structure relates to environmental differences, modern sites were
classified into environmental groups based on factors such as latitude, precipitation and
temperature using Baileys ecoregions.
Another focus of this chapter is a review of theories about the dispersal of African
mammals, and Homo in particular, to new regions. Ideas considered include the
simultaneous dispersal of a group of African mammals, including hominins, out of
Africa, and the idea that hominin dispersal was linked to the spread of savanna habitats.
These theories, as well as other habitat information about the Plio-Pleistocene sites will
be considered in light of results presented in the following chapters of the dissertation.
Finally, the specific sites in East Asia and East Africa to be analyzed were
introduced, along with general climatic and environmental conditions in the two regions.
East African sites were from Olduvai Beds I and II and East and West Turkana. East
Asian sites included both hominin and non-hominin localities. The East African Plio-
Pleistocene shows a trend toward increasing aridity and variability after 3 Ma, with
habitats becoming more open, while East Asia experienced glaciation and cooling after
3.5 Ma, with decreases in precipitation after 2.6 Ma.
41
Chapter 3: Methods to determine ecological similarity
This research is concerned with the ecological context of the initial hominin
dispersal out of Africa. Specifically it looks at the degree of ecological similarity between
communities of mammals in East Asia and East Africa and compares the ecology of East
Asian communities during the Plio-Pleistocene. Ecological similarity is defined as the
similarity between animals based on the ecological properties of diet, body mass and
substrate use (i.e., terrestrial, arboreal or aquatic). Similarity in community or ecological
structure implies communities with similar proportions of ecologically comparable
animals. Ecological community structure methods are based on the principle of
convergence of environmental conditions; i.e., communities from similar environments
will have similar structures (Andrews 1996). Ecological structu
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