Mutations in thousands of genes that govern our intelligence are contributing to a 'dumbing down' of humanity, as claimed in a controversial new theory. It is argued that the development of civilisation has eliminated the natural selection that would have prevented these intellectually harmful mutations from being passed down through the generations.
'I would wager that if an average citizen from Athens of 1,000 BC were to appear suddenly among us, he or she would be among the brightest and more intellectually alive of our colleagues and companions, with a good memory, a broad range of ideas, and a clear-sighted view of important issues' said study author Professor Gerald Crabtree, developmental biologist at Stanford University.
Professor Crabtree's theory is derived from calculations on how often harmful genetic mutations occur and his estimation that as many as 2,000 to 5,000 genes contribute to our intellectual and emotional abilities. The theory estimates all humans have undergone at least two mutations that are harmful to our intellectual or emotional abilities in the last 3,000 years. In the past, when humans were still hunter-gatherers, Professor Crabtree posits that such a mutation could have been fatal.
'A hunter-gatherer who did not correctly conceive a solution to providing food or shelter probably died, along with his or her progeny, whereas a modern Wall Street executive that made a similar conceptual mistake would receive a substantial bonus and be a more attractive mate. Clearly, extreme selection is a thing of the past'.
Not everyone is convinced by this theory, however. Professor Robin Dunbar, an anthropologist at the University of Oxford told the Daily Telegraph that 'in reality what has driven human and primate brain evolution is the complexity of our social world [and] that complex world is not going to go away. Doing things like deciding who to have as a mate or how best to rear your children will be with us forever'.
Professor Steve Jones, a geneticist at University College London, also pointed out to The Independent that the article is based on educated guesswork. 'Never mind the hypothesis, give me the data, and there aren't any. I could just as well argue that mutations have reduced our aggression, our depression and our penis length, but no journal would publish that. Why do they publish this?'.
Professor Crabtree asserts that by the time these mutations arise scientific methods will have been developed to counteract their harmful effects.
'I think we will know each of the millions of human mutations that can compromise our intellectual function and how each of these mutations interact with each other and other processes as well as environmental influences. At that time, we may be able to magically correct any mutation that has occurred in all cells of any organism at any developmental stage'.
The study was published in the journal Trends in Genetics.