Biological Anthropology

Biological Anthropology

Content

Scientific theory and evolution

Natural selection

Primate mating strategies

Exercise: human mating strategies

Scientific TheoryA fundamental component within biological anthropology is the scientific theory.

A theory describes and explains observable and observed events and predicts future events.

A theory is usually confirmed if the actual observations agree with the predictions.

A theory can be viewed as a group of related hypotheses that have repeatedly been tested and not rejected. (Popper’s falsifiability)

Ultimately, theories cannot be proven.

Theories are not static entities either.

Scientific Theory

attempts to provide systematic and supported explanations

one way of looking at the world

a perspective and mechanism for asking how and why questions

is not static but dynamic in nature

is explanatory and organising, relating concepts to data or facts;concerns itself with natural (not supernatural) observations and phenomena. (positivist)

Scientific Theory

Scientific explanations are…

tentative and subject to change;do not attempt to provide ultimate answers; are not dogmatic or based on faith.

Is this as true for social sciences as natural sciences?

Evolution

Evolution - the cornerstone of Biological Anthropology

Evolution = change in a population over time

Evolution is a FACT

How evolution works is a THEORY

see “Evolution is a Fact and a Theory” by Laurence Moran (avialable on DUO)

Who let the dogs out?

Artificial Selection

Darwin’s 3 postulates

The struggle for existence (Malthus)

Variation in fitness

Inheritance of variation

Biological Anthropology

Primatology

Primatology: the study of the biology, evolution, behavior, and social life of primates

Primates evolved about 70 million years ago

The Hominid lineage diverged some 8 million years ago

Consequently we share many physical characteristicsand behavioural characteristics with living primates

Primatoligists

• Observation• What kinds

of things do they observe?

Group work

• From your reading:-– Which characteristics do we share

with other primates?• Biological and behavioural

– How do humans differ?– Speculate how these differences

emerged

Break time

Primate Mating Systems

Reproduction is the single ultimate purpose of every living thing

Evolutionary adaptation is based on differential success of traits within a population

Both physical and behavioural characteristics are therefore subject to evolutionary pressure

As a consequence, mating systems play a crucial role in understanding primate societies

Evolution of reproductive strategies

Understanding the diverse reproductive strategies of non-human primates illuminates human evolution because we share many elements of our reproductive physiology with other species of primate.

Reproductive strategy is not a conscious plan, it is a set of behaviours that occur in a specific functional context as the product of natural selection. As such they can be considered in terms of both cost and benefit.

The amount of time, energy and resources that the males and females of a species invest in their offspring has profound consequences for the evolution of virtually every aspect of their social behaviour and many aspects of their morphology

Evolution of reproductive strategiesPrimate females always provide extensive care for their young whilst males do so only in a few species.

In contrast with some other species

Evolution of reproductive strategiesMales do not care for their offspring when…

They can easily use their resources to acquire additional matings, or

When caring for their offspring would not appreciably increase the offspring’s fitness.

Evolution of reproductive strategiesThe mammalian reproductive system commits primate females to invest in their offspring.

Female mating strategies

Female primates invest heavily in each of their offspring.

A females’ reproductive success depends largely on her ability to obtain enough resources to support herself and her offspring.

Female mating strategies

High-ranking females tend to reproduce more successfully than do low-ranking females.

Female mating strategies

Females must make a trade-off between the number of offspring they produce and the quality of care they provide.

Male mating strategies

Sexual selection leads to adaptations that allow males to compete more effectively with other males for access to females.

Sexual selection is often much stronger than ordinary natural selection and can run counter to it.

Male mating strategies

There are two types of sexual selection…

Intrasexual selection results from competition among males, and

Intersexual selection results from female choice.

Intrasexual selection

Male mating strategies

In multimale, multifemale groups, where females mate with several males during a given estrous period, sexual selection favours increased sperm production.

Intersexual selection

Intersexual selection favours three kinds of traits amongst males…

Those that increase the fitness of the females

Those that indicate good genes and thus increase the fitness of the offspring

Non-adaptive traits that make males more conspicuous to females.

Male reproductive tactics

Investing males…

Monogomous pair-bonding is generally associated with high levels of paternal investment. This does not ensure fidelity though, and although the male may copulate fairly freely he generally keeps an eye on the female.

Male – Male competition in nonmonogomous groups

For males in nonmonogomous groups, reproductive success depends their ability to gain access to groups of unrelated females and to obtain matings with receptive females.

Male – Male competition in nonmonogomous groups

In species that normally form one-male groups, males compete to establish residence in groups of females.

Male – Male competition in nonmonogomous groups

Residence in one-male groups does not always ensure exclusive access to females. Incursions by groups of males are sometimes experienced during the mating season.

Male – Male competition in nonmonogomous groups

For males in multi-male groups, conflict arises over group membership and access to receptive females.

Infanticide

Infanticide is a sexually selected male reproductive strategy, linked to changes in male membership and status.

Infanticide

Infanticide is not restricted to males.

Primate Ecology

Studying primate behaviour may offer us an insight into human evolutionary history – and contemporary human behaviour

But we need to be careful of anthropormorphism

Activity

•Get into small homogenous (gender, culture) groups of 2-4

•Discuss human male/female mating strategies

•Monogamous pair bonding? (how are mating pairs selected?)•Natural selection? (Darwin’s postulates)•Sexual selection? (Inter/ intra?)

What is the future for humanity?

Further reading…

“The Future of Man--How Will Evolution Change Humans?” – Scientific American

Available in teaching materials (with some other readings) and in external links

Next week…

Linguistic Anthropology