That we are 98.4 per cent genetically identical to chimpanzees is one of the more misleading factoids of our time. Genes have proved to be so complicated that this figure needs to be treated with extreme caution. For decades, 97-98.5 per cent of the genome (the complete set of genes in an organism) was dismissed as junk because it had no obvious function. The remaining tiny portion was known to be the blueprint for all proteins and hence other substances in the living body. Facetiously, we might once have wondered if it is merely the junk we share with chimpanzees.
That is not the case: all living things use the same cellular machinery, and in that sense we are also 30 per cent banana. What matters is the recent knowledge that some "junk" contains regulatory genes that have enormous leverage on the protein-coding genes. In Not a Chimp, the TV science producer and director Jeremy Taylor gives case histories of the search for those crucial genes that make us human. The FOXP2 gene, for instance, discovered in a family with a history of language difficulties, is now known to be important for speech and comprehension in humans and, amazingly, for the ability of birds to sing.
A whole suite of genetic rearrangement is emerging. Anyone looking at the chimpanzee skeleton and ours, with their differently proportioned limbs, would guess that the timing of the processes of bone growth must be very different. How long a gene is expressed (which is controlled by regulatory genes) can be more important than changing the gene itself.
That 98.4 per cent similarity has fuelled a movement to accord chimpanzees human rights. However, Taylor demonstrates that if we are looking for the nearest thing to human intelligence, it seems to reside not in chimps, but in birds – especially crows. The record of human evolution will become dramatically clearer in five to ten years time. Meanwhile, for an idea of why we are more than a chimpanzee plus 1.6 per cent, start here.Reuse content