The popular idea that the close genetic similarity between humans and chimps is evidence of a close evolutionary relationship between them has been taking a beating of late. A new book by Jeremy Taylor titled Not a Chimp: The Hunt to Find Genes That Make Us Human adds to the drubbing. Taylor pronounces the inference from genetic similarity to close relationship to be without any merit. The book is reviewed at New Scientist by Ewan Calloway who writes that:
[T]he former BBC producer [Taylor] synthesizes recent genetic, behavioural and neuroscientific research to argue that far more than a handful of genes divides humans from our evolutionary cousins, 6 million years removed.
Take that 98.4 per cent [the percentage of our DNA we share in common with chimps], an oft-repeated figure that has been used to argue that chimps deserve human rights. True, Homo sapiens and Pan troglodytes share an extraordinary amount of genetic similarity - yet humans and mice share almost as much.
Complete genomes of both species are enabling researchers to map the chasm between human and chimp, which seems to deepen by the year. A good example is FOXP2, a regulatory gene linked to speech and language disorders in humans. FOXP2 in chimps has barely changed in the 130 million years since primates and mice diverged from their common ancestor. But after humans and chimps split, two key changes accumulated on the human line.
Even greater differences may lurk in the areas of the genome once discounted as "junk" DNA, which don't make proteins but instead determine gene activity. One recently discovered RNA-coding sequence that may be involved in cerebral cortex development was found to vary little between chimps and chickens, yet humans possess 18 unique changes.
Geneticists are right to home in on differences that affect brain development: nowhere is the gulf between humans and chimps wider than in their mental abilities. Psychologists suggest that the ability to infer the mental states of others may underlie language and culture. Children gradually acquire this capacity...but evidence for it in chimps is equivocal.
....Not a Chimp should be mandatory reading for journalists who often reinforce the general public's misconception that chimps are practically human.
It may be that chimps and man have a common ancestor, but the more we learn the harder it is to make that case without resorting to question-begging - e.g. The similarities in DNA between chimp and man result from their evolutionary kinship. This must be the explanation for the similarities because we know they are evolutionarily related.
Another recent development in this regard, bye the bye, is the mounting skepticism in the scientific community surrounding the proper interpretation of the fossilized remains of an early hominid named Ardipithecus ramidus (Ardi, for short) that was initially touted as a missing link between man and chimp. It's now beginning to look, however, like Ardi is not at all close to being a human ancestor.
I wonder how many more times we're going to be told by journalists on the front page of the newspaper that the "missing link" has been discovered only to learn six months later on page twenty that such claims were premature.
RLC
