1 Human evolution involves a combination of genetic and cultural change.

2 Genetic change brought about an extremely rapid growth of the human brain, with a 3.2-fold increase in the volume of the cerebral cortex alone from the time of Homo habilis 2 million years ago to the appearance of early Homo sapiens about 500,000 years ago, accompanied by profound architectural innovations in the larynx and speech centres of the brain. Cultural change is much faster, but it is limited and directed by the restricting properties of the brain and sensory apparatus.

3 The interaction of biological and cultural evolution, remains largely unexplored. Human social behaviour is transmitted through learning and culture.

4 The distinctive properties of cognition, ranging from a sensory perception to memory and decision making, have a powerful effect on culture.

5 Culture is determined ultimately by the mental development of individual human beings. The properties of this development can be characterized by regularities of development rules that bias behaviour in a particular direction. For example, human beings are highly audiovisual and depend very little on smell and taste in comparison with the great majority of animal species. This biological property redounds to a much richer vocabulary describing hearing and vision than is the case for smell and taste. In various languages around the world, about two-thirds to three- fourths of all the words applying to the senses describe hearing and vision, while one-tenth or fewer describe smell and taste.

6 Genetic evolution thus affects cultural evolution. Conversely, cultural evolution affects biological evolution, by creating the environment in which the genes that determine development epigenetic rules are selected through natural selection. Genes and culture are in fact inseparably linked. Changes in one inevitably force changes in the other, resulting in what has come to be called gene-culture coevolution.

7 The process is believed to occur as follows:

• The genes prescribe the biochemical processes of development by which the individual mind is assembled.
• The mind grows by processes of mental development as the growing individual assimilates aspects of the culture already in existence. Culture is carried forward from generation to generation the sum of past and present decisions and innovations of all members of the society.
• Some individuals possess genes that enabling them to survive and reproduce better in the contemporary culture than other individuals. Survival is enhanced either by direct selection, of descendants, or by supporting collateral kin in addition to direct descendants.
• The more successful developmental processes spread through the population, along with the genes that encode them. The population evolves genetically with reference to the processes of development.

 8 Culture is created and shaped by biological processes while the biological processes are simultaneously altered in response to cultural change. However, the rates at which the two forms of evolution occur and the tightness of the linkages between them remain largely , unsolved problems.