By Mark Prigg
PUBLISHED:13:57 EST, 12 November 2012| UPDATED:14:10 EST, 12 November 2012
Our intelligence and behaviour requires optimal functioning of a large number of genes, which requires enormous evolutionary pressures to maintain.
Now, in a provocative theory, a team from Stanford University claim we are losing our intellectual and emotional capabilities because the intricate web of genes which endows us with our brain power is particularly vulnerable to mutations – and these mutations are not being selected against our modern society because we no longer need intelligence to survive.
But we shouldn’t lose any sleep over our diminishing brain power – as by the time it becomes a real problem technology will have found a solution making natural selection obsolete.
‘The development of our intellectual abilities and the optimisation of thousands of intelligence genes probably occurred in relatively non-verbal, dispersed groups of peoples before our ancestors emerged from Africa,’ says Dr Gerald Crabtree, lead author of the paper published today in Cell Press journal Trends in Genetics.
In this environment, intelligence was critical for survival, and there was likely to be immense selective pressure acting on the genes required for intellectual development, leading to a peak in human intelligence.
But it was downhill from there on in as, from that point, it’s likely that we began to slowly lose ground, the researchers claim.
With the development of agriculture, came urbanisation, which may have weakened the power of selection to weed out mutations leading to intellectual disabilities.
Based on calculations of the frequency with which deleterious mutations appear in the human genome and the assumption that 2,000 to 5,000 genes are required for intellectual ability, Dr Crabtree estimates that within 3,000 years, about 120 generations, we have all sustained two or more mutations harmful to our intellectual or emotional stability.
Also, recent findings from neuroscience suggest that genes involved in brain function are uniquely susceptible to mutations.
Dr Crabtree argues that the combination of less selective pressure and the large number of easily affected genes is eroding our intellectual and emotional capabilities.
But the loss is quite slow, and judging by society’s rapid pace of discovery and advancement, future technologies are bound to reveal solutions to the problem, Dr Crabtree believes.
He said: ‘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.
‘Thus, the brutish process of natural selection will be unnecessary.’
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