Explaining human uniqueness: genome interactions with environment, behaviour and culture

Abstract

What makes us human? Specialists in each discipline respond through the lens of their own expertise. In fact, 'anthropogeny' (explaining the origin of humans) requires a transdisciplinary approach that eschews such barriers. Here we take a genomic and genetic perspective towards molecular variation, explore systems analysis of gene expression and discuss an organ-systems approach. Rejecting any 'genes versus environment' dichotomy, we then consider genome interactions with environment, behaviour and culture, finally speculating that aspects of human uniqueness arose because of a primate evolutionary trend towards increasing and irreversible dependence on learned behaviours and culture - perhaps relaxing allowable thresholds for large-scale genomic diversity.

Figure 1. Structural variations and segmental duplications

a Example of structural variation and segmental duplication difference between chimps and humans. An interspersed segmental duplication (33,405 bp) carries a copy of the rapidly evolving nuclear pore complex interacting protein gene (NPIP), a member of the morpheus gene family, into a new location on chromosome 16. The chimpanzee insertion results in a coordinated deletion (16,100 bp) of the serine protease EOS gene. As a result, chimpanzees carry an additional copy of the morpheus gene, carried within the duplicon LCR16a (low-copy repeat 16a), but have lost a serine protease gene that is present in humans. Blue lines identify regions of high sequence identity between chimpanzees and humans. b Human segmental duplication expansion on chromosome 16. Nine single-copy regions in Old World monkeys (as indicated on the baboon Papio hamadryas (PHA) chromosomal ideogram) became duplicated specifically within the human–great ape lineage of evolution. These loci were distributed to 31 different locations on human chromosome 16; 24 of these carry a human–great ape specific gene family known as morpheus (as indicated by the red-coloured duplicons). Rearrangements between these interspersed duplications are associated with mental retardation and autism in humans. Coloured blocks show the distribution of the duplicons between the two species, with the position of the ancestral loci indicated by asterisks. Figure is modified, with permission, from REF. © (2006) National Academy of Sciences, USA.

Figure 2. Are human genomes escaping from Darwinian natural selection and Baldwinian fixation of learned behaviours?

The figure shows potential mechanisms of behavioural and cultural buffering of genomic changes, potentially allowing hominid genomes to partially escape Darwinian selection and avoiding the need for the final phase of the Baldwin effect, in which learned behaviours eventually become hard-wired in the genome. The potential feedback loops shown could accelerate such processes, and even make some of them irreversible. See the main text and BOXES 5,6 for further discussion.