Book reviews

Journal of Human fhlu/ion ( I990) 19, 327-334

Mammalian Dispersal Patterns: The Effects of Social Structure on Population Genetics

Edited by B. Diane Chepko-Sade and Zuleyma Tang Halpin (1987). Chicago: Tht

University of Chicago Press. xviii + 342 pp. $50.00 (cloth), $19.95 (paper). ISBN

0-226-10266-l (cloth), ISBN o-226-10268-8 (paper).

This book is a valuable addition to the literature describing the interactions of social

organization, migration and population genetic structure. The papers included present a

wide range of field data, ideas and analytic approaches, and the editors summarize and

integrate the diverse contributions much better than is usually the case in volumes such as

this. On the whole, the book achieves its stated purpose: “to bring together the work of‘

animal behaviorists, wildlife biologists, and anthropologists who are doing long-term

longitudinal studies of social organization and dispersal patterns with that of population

geneticists who are interested in the evolutionary causes and consequences of dilferent

patterns ofsocial organization (p. xii).” The book does not resolve long-standing problems,

but no treatment of these issues could.

The text totals 19 chapters, but for anthropologists or primatologists it can be divided

into two major sections plus an introduction. The introduction, supplied by \;t’. Shields,

attempts to define terms and focus attention on specific issues. While this ambition is

commendable, Shields’ presentation will not satisfy many primate biologists. Several ofhis

definitions are problematic from the point of view of primate population structure and

dynamics (see below).

Chapters Two through Twelve present results of long-term observation of mammalian

populations. No primate species are discussed here, and so the section may be of limited

interest to primate chauvinists, but these studies, like Shields’ introduction, can contribute

signiftcantly to primatologists’ understanding of the relationships among variables. I found

the chapters byJ. Berger on wild horses, J. P. Rood on dwarf mongooses, Z. T. Halpin on

prairie dogs, and W. Z. Lidicker and J. L. Patton on four small rodents particularly strong.

One should bear in mind how few long-term data on primate dispersal are available, and

that many aspects of social organization are shared among these species and many

primates.

328 ttooli KCvIEwS

The rest of the volume will he of more direct interest to anthropologists. First are two

excellent papers describing human populations. E. O’Brien presents analyses ofsocial and

genetic structure among Canadian and American Hutterite communities. Next, P. E.

Smouse and J. W. Wood discuss genetic structure in the Gainj of New Guinea, presenting

innovative analytical techniques that combine migration matrix and isolation-by-distance

methods and deserve wide attention. D. S. Sade, B. D. Chepko-Sade, M. Dow and ,J.

Cheverud present a migration matrix analysis of inter-group migration of rhesus monkeys

on Cayo Santiago. Their method, which uses multistate lifetables, is a more accurate

representation of migration for species in which movement between social groups occurs

repeatedly during the reproductive phase of the life cycle.

The papers in the next set are more theoretical. P. M. Waser discusses a model of

dispersal and M. J. W d a e and F. J. Breden consider the relationship between population

structure and evolution through kin selection. The most stimulating of this group is a paper

by A. Templeton interpreting observations on inbreeding and outbreeding depression in

mammals. His conclusion, which contradicts the conclusions of the editors to he discussed

below, is that mammalian populations do not generally consist of small, relatively inbred

demes.

The concluding chapter, written by Chepko-Sade and Shields with the help of six of the

other contributors, does an admirable job of drawing together the diverse strands of data

and theory presented throughout the book. The various datasets and theoretical

treatments defy complete synthesis, but fortunately that’s no deterrent to Chepko-Sade

and Shields, who focus their attention on the determinants and effects of “eflective

population size”. Their effort is worthwhile.

In his introduction, Shields presents an important problem facing anyone trying to

synthesize data and analyses relevant to this topic. He attempts to develop definitions for a

number of critical terms that could be used in all contexts. While his definitions may be

applicable to some mamalian species, many of them cannot be used in studying primates.

For example, deme is defined as “[t]h e random-mating population. It is the breeding

group within which parents are drawn at random, that is, all breeding males and females

have equal probabilities of mating (Mayr, 1963; Dobzhansky, 1970) .” References to the old

masters aside, this definition cannot apply to cercopithecoid or hominoid social groups,

since the observed rates of inter-group migration make the breeding population much

larger than any single social group. Nor can it apply to sets ofgroups, because complexities

such as non-random patterns of migration and intra-group social dominance make it

unlikely that any set of social groups will constitute a random-mating population. If the

term is meant to refer to hypothetical collections of animals, then we are left once again

with theory crossing paths with, but never actually engaging, the empirical data. Trying to

reconcile theoretical and operational definitions of deme and other concepts such as

effective dispersal or outbreeding is a major recurrent problem, but Shields’ definitions do

little to improve the situation.

In the end, Chepko-Sade and Shields argue that overall the data suggest mammalian

populations have generally small effective sizes and consist of partially isolated, mildly

inbred demes. They acknowledge that this is at odds with Templeton’s conclusions. A

number of different hypotheses are available that could reconcile these views.

The problems addressed in this book are extraordinarily complex, but so important to

evolutionary analysis of mammalian populations that they must be addressed. Explicitly

or not, several currently unresolved issues in primatology and biological anthropology

ROOIi REVIEWS 329

depend to some degree on the measurement of population genetic structure. What

proportion of primate social behaviors evolved through kin selection or strict individual

selection? The relationships between social organization, patterns ofkinship within groups

and population genetic structure are central to this question. Did anatomically modern Hanzo sapiens simply replace archaic populations in Western Europe and Asia, or is there temporal genetic continuity across that morphological transition? The answer depends to some degree on the pattern of gene flow in hominid populations. When gene flow is quite limited geographically, morphological transitions occurring in one place may not be

transferred to distant populations except by competition and replacement. If gene flow is

quantitatively greater and geographically wider, no population evolves independently. This collection ofpapers is a very useful addition to the literature, because it achieves its

goal of bringing together data and theory relevant to these problems. Careful attenti(~n to these papers and the issues raised is warranted.

JEFFREY ROGEKS

Department qf ,Gzthropolog~, Yale liniversil_z~,

Box 2114 Yak Station, ,Ve!ew Haven. CT 06520, I:..T.:I.

References

Reproductive Success: Studies of Individual Variation in Contrasting Breeding Systems

Edited by T. H. Clutton-Brock (1988). Chicago: University ofChicago Press. ix + 538 pp.

$29.95 (paper). ISBN O-226 11059- 1.

This hefty volume with its striking M. C. Escher cover contains a wide samplingofthe data that WC now have on phenotypic and environmental correlates of li&time reproductivt SUCC~W (LRS) in animals. It is organized taxonomically. The empirical chapters cover fivr

insects, two frogs, twelve birds and six mammals, including three primates: vervets (Chcnry, Seyfarth, Andelman and Lee), yellow baboons (‘J. Altmann, Hausfater and S. A. Altmann) and humans- the Kipsigis (Borgerhoff Mulder). Each author was to address

four main issues set forth in the introdu~tioI1 by T. H. Glutton-3ro~k: the extent of \:ariation in male versus female LRS; the relative contrjbutions of longevity, Fecundity or mating success and offspring survival to LRS; the role ofage in the reproductive success of

individuals; and the determinants of male versus female success across different mating

systems. Following the empirical papers are three more conceptual chapters. David Brown discusses methods for partitioning the sources of variance in reproductive success, including his own which is used by a number of’contributors. Alan Grafen admonishes empiricists on the proper use of their results. He emphasizes that data on lifetime

reproductive success generally tell us more about current selection tflan how or if traits are adaptive. Finally, Glutton-Brock provides an overview and some synthesis of thr data papers in terms of the original four questions.

These issues are clearly of interest to evolutionary biologists whatever their particular I&i. Not only are they fundamental to our understanding current selection in natural populations, but they also link demography to evolutionary change. They underlie our