Chapter 8

Primate Models for

Human Behavioral Evolution

Developmental Changes in the Skull of Chimpanzees and Humans

(a) Chimpanzee and (b) Human. Anatomical differences arise through changes in regulatory genes in one or both species.

Human Origins and Behavior

Primatologists still use nonhuman primate behavior to examine the evolution of human behavior, they also use statistical tests to examine relationships between variables.

Brain and Body Size

The relationship between body and brain size is the index of encephalization.

Modern humans have a brain size well beyond that expected for a primate of similar body weight.

Allometry, also called scaling; is the differential proportion among various anatomical structures.

Cortex and Neocortex

Comparisons of Mammalian Brains

Language

Human trait. – Some animals go beyond involuntary noise

responses• Vervet monkeys

SymbolicArbitrary

Language

The bonobo Kanzi, as a youngster, using lexigrams to communicate with human observers.

Left Lateral View of the Human Brain

Information that is to be used in speech is sent from Wernicke’s area, via a bundle of nerve fibers, to Broca’s area.

Evolution of Human Language

Primate Cultural Behavior

Cultural behavior makes primates attractive as models for behavior in early hominids.

Culture is Learned

(a) This little girl is learning how to use a computer by watching her older sister.

(b) A chimpanzee learns the art of termiting through intense observation.

Using Tools

Chimpanzees in Bossou, Guinea, West Africa, use stones as hammer and anvil to crack oil-palm nuts. The youngster is learning to use stone tools through observation.

Criteria for Cultural Acts in Other Species

Innovation

Dissemination

Standardization

Durability

Diffusion

Tradition

Nonsubsistence

Naturalness

Aggressive Interactions

Members of a chimpanzee “border patrol” at Gombe survey their territory from a tree.

Altruism

Behavior that benefits another while involving some risk to the performaer

The Primate Continuum

Human brains are larger than primate brains, but the neurological processes are functionally the same.