Biological Anthropology Subfields

and Hadza film Notes

Some Biological Anthropology Subfields •  Population genetics: the study of gene frequencies and changes in them over evolutionary

time; also in biology departments •  Primatology: the study of the order to which we belong (morphology, phylogeny, ecology, and

behavior); also in zoology departments •  Paleoanthropology: the study of ancient humans as found in fossil hominid evidence such as

petrified bones and footprints—uses many archaeological methods •  Bioarchaeology: a subfield of both archaeology and biological anthropology (includes

forensics); the film “The Perfect Corpse” in the Archaeology portion of our class involves bioarchaeology

•  Human variation: the study of ways in which different populations express different physiological properties (e.g., skin color variation by region, lactose tolerance)

•  Human evolutionary biology: how do the human body’s physiological adaptations work, and why do we have them? (for example, do fevers have a beneficial function which can explain why they evolved?)

•  Behavior genetics: can inter-individual differences in morphology and behavior be attributed to inter-individual differences in one’s genetic makeup?; emphasizes differences

•  Evolution of behavior and mental processes: –  Human behavioral ecology: how do ecological variables impact human behavior and reproduction? –  Evolutionary psychology: how did natural selection shape the mind’s adaptations in ancestral

populations, and how are those mental adaptations expressed in measurable behaviors?; emphasizes a universal human nature,

–  Both fields examine inter-individual differences in terms of responses to different environments, experiences, and cultures

Subfields

•  Not all BioAnthro subfields look specifically at how evolutionary processes shaped humans and their relatives, BUT, all agree that evolution DID shape us

•  For example, a bioarchaeologist might study the chemical components of Bronze Age teeth to infer the dietary differences of a wealthy individual vs. a poor individual, without necessarily having a hypothesis related to the evolution of human diets or the evolution of the shapes of the teeth

•  Not all BioAnthro subfields look specifically at how genes affect humans and their relatives, BUT, all agree that genes do build proteins--the stuff we are made of

•  For example, we do not know what genes build the proteins that make upthe heart, but we do know that evolution (specifically, evolution by natural selection) shaped an organ that was sufficient to pump blood through the body and lungs, with the effect of delivering oxygen and nutrients to various body structures

•  Some subfields are subfields in disciplines other than anthropology

The Hadza •  The Hadza are an ethnic group in central Tanzania, living around Lake

Eyasi in the central Rift Valley and in the neighboring Serengeti Plateau. The Hadza number under 1000. Some 300-400 Hadza live as, hunter-gatherers much as they have for thousands, or even tens of thousands, of years; according to some anthropologists, they are of the last few functioning hunter-gatherers in Africa.

•  The Hadza are not closely related to any other people. While traditionally considered an East African branch of the Khoisan peoples, primarily because their language has clicks (see Pinker 167-168). The Hadza language appears to be an isolate, unrelated to or very distantly related to any other language. (e.g., 8 noun classes).

•  The Hadza still subsist by hunting and gathering-foraging—which is what hominids (including our ancestors) did for millions of years during and prior to the evolution of anatomically modern humans (us)

•  The lifestyle of the Hadza may be one of the world’s current best indicators of what life was like when humans evolved

•  Film (39 mins.) and how to take notes during a film

Hand Notes on “The Hadza”

Some notes on “The Hadza” •  Huts put up by women •  They are hunter-gatherers (HGs) •  Men hunt alone •  Women gather plant foods •  Hunt many impala •  Men gamble in downtime, winning and losing mainly arrows but also bees, honey; gambling losses do not cause significant

hardships ad arrows can be replaced by making new ones within hours to days •  No territoriality--people HG anywhere they want, unlike in most other HGs studied to the time the film was made •  All hunting by adult men is with bow and arrow; no traps, snares, or nets; the force require to pull a bow is strong--throws

off accuracy but implants arrow more deeply; 90% misses in hunting (often due to inaccuracy point above) •  Arrows with metal heads traded with other groups (for, e.g., honey) •  Majority of food from wild berries and roots/tubers, though they consider themselves meat-eaters •  Berries are abundant and many are eaten on the spot; food not stored past a day’s worth of eating (some seasonal

variation) •  Women about 2 hrs a day gathering all the food they need •  Baobob trees have tasty fruits (ground and cooked to a porridge); some trees better than others; berries are not like sweet

wildberries--harder to eat; roots and tubers cooked; water from underground sources and water trapped in tree hollows that are scarce during the dry season

•  Baobob and other locations have bees with honey and grubs •  Honey can be traded to other groups for western items like pots, tobacco, cloth, axes, iron/aluminum, beads •  One male duo did not find sufficient honey in one tree to walked a few miles to another known bee source •  Only collect enough food to last until the next day •  Dry months = more berries; wet months = more roots/tubers which are then more succulent •  Grandmas collect large tubers and share them with everyone in the camp--not just their specific families •  Hadza are nomads who only live in a particular camp for up to a few weeks •  Sometimes live on rock shelters--important returned-to shelters are on hills which provide a good vantage point of

surrounding areas •  An impala is killed; hidden from scavengers like vultures and hyenas until the hunter comes back with others to help carry

the carcass to camp •  The fat, not so much the meat, is what is prized in the impala--most hunted foods are high in protein but low in fat •  Boys practice hunting at young ages with wooden-tipped bows and arrows •  Boys catch a hyrax and use it to procure additional hyraxes, than kill & eat them all (no waste and yet no saving food)

Parental Investment and Sexual Selection

Trivers 1972

Assumption •  Assumption: Every organism has adaptations that

function to facilitate reproduction •  Members of a population/species live in the same

environment, so why do some animals have different adaptations than others?

•  Morphs: age, sex, others •  SEX: male and female adaptations are different •  WHY?

Parental Investment

•  Any investment by the parent in an individual offspring that increases the offspring’s chance of surviving (and hence reproductive success) at the cost of the parent’s ability to invest in other offspring” (Trivers 1972)

Sperm vs. Egg

In sexually-reproducing species, the relative size of gametes define who is male and who is female.

Nurturant Females

•  In most animals, and almost all mammals, females provide far more parental investment than just the egg

•  Internal fertilization protects, but at a cost

•  Cod vs. gorillas •  Humans (mammals):

–  Prolonged internal gestation (pregnancy)

–  Placentation –  Lactation

Competitive Males •  Males are fighting with each other to mate with as

many females as possible •  More females = more offspring (sharp contrast to

females)

Sexual Selection and Parental Investment Theory

•  For members of the sex that invests more in offspring, reproductive success is limited by the amount of resources an individual can secure for itself and it’s offspring

•  For members of the sex that invests less in offspring, reproductive success is limited by the number of mates one can acquire

Sexual Selection and Parental Investment Theory

•  What of it? •  Selection acted on males differently than it acted on females •  Specifically, differences in parenting strategies cause differences in

adaptations •  Sex that invests more: adaptations to survive and get resources for

offspring •  Sex that invests less: adaptations to help them get as many mates

as possible •  It explains why, in many species, males look and behave differently

than femalesWhen the sexes have different adaptations, they are “sexually dimorphic”

•  Intrasexual selection:weaponry/size differentiation

Sexual Selection and Parental Investment Theory

•  Intrasexual selection: lack of differentiation

Sexual Selection and Parental Investment Theory

•  Intersexual selection: ornaments in one sex and not the other

Sexual Selection and Parental Investment Theory

•  Intersexual selection: why ornaments? •  Arbitrary (you just know you want your

offspring to inherit those traits) •  Good genes •  Low parasite load •  Handicap principle •  Combination

Sexual Selection and Parental Investment Theory

Sexual Selection and Parental Investment Theory

•  Why not just say “females are limited by resources and males are limited by access to females”?

•  The exceptions that prove the rule

seahorse

phalarope

•  Paternal confidence is typically less than maternal confidence

•  If fathers invest, as they do in humans, the father needs to be sure he is, in fact, the father

•  Sexual jealousy •  Acute anger at cuckoldry

Paternity Uncertainty

Next Topic

•  Altruism

The Problem of Altruism

Kin Selection Reciprocal Altruism

Altruism •  Doing something that benefits another

individual’s reproductive success at a cost to one’s own reproductive success

•  If natural selection is all about competition to reproduce, how could there possibly be adaptations that cause one to be altruistic?

•  Two solutions –  Kin selection –  Reciprocal altruism

Kin Selection •  William Hamilton •  Not about helping the individual but about helping the

gene •  You share genes with your relatives •  Your gene helps make copies of itself by helping close

relatives reproduce too

Kin Selection

•  Mom, dad, full siblings: 50% (1/2) •  Grandparents, 1st uncles and aunts, and

half siblings: 25% (1/4) •  First cousins: 12.5% (1/8) •  Identical twins: 100% •  Bees: weird; workers are more closely

related to each other than to the queen; Hamilton’s work

Reciprocal Altruism

•  Altruism among Unrelated individuals •  I.e., “exchange” •  Trivers (again)

Natural Selection Behavior

•  What is the nature of the relationship between natural selection and behavior?

•  It has to do with genes getting reproduced over generations •  Genes reproduce or fail to reproduce over generations via their

ability to produce protein structures (adaptations) that diminish or enhance reproduction.

•  So far we have looked at bodily structures comprising those proteins (e.g., opposable thumbs)

•  Evolutionary perspectives on human behavior consider psychological adaptations, that is, protein structures in the brain (neurons and neural circuits)

•  The brain is what causes behavior

Genes Proteins Bodies

DNA Protein

Cell parts and cell

Amino acid Amino acid strand

Tissue Organ Body

Genes Proteins Bodies

DNA Protein

Cell parts and cell

Amino acid Amino acid strand

Tissue Organ: the brain

Body

Genes Behavior

The brain is what causes behavior

Neural Circuits are made of protein