Technology might be causing human beings to 'evolve backwards' - and become stupider.
The 2000 to 5000 genes required to maintain our high intelligence are particularly susceptible to mutation - and a report in scientific journal Trends in Genetics suggests that easy-to-use technologies such as sat-nav and the internet mean we no longer need these abilities as much.
As a result, humans will begin to mutate to 'lose' abilities and become stupider - and the process may have already begun.
The development of our intellect may have 'peaked' when we lived in small groups in a highly dangerous environment in prehistoric Africa.
Scientists writing in the journal Trends in Genetics suggest that humans will incur mutations that damage our intellectual and emotional ability - abilities we no longer 'need'.
Most humans will have sustained one or two damaging mutations within 120 generations, around 3,000 years.
"The development of our intellectual abilities and the optimization 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, of Stanford University.
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.
From that point, it's likely that we began to slowly lose ground. With the development of agriculture, came urbanization, which may have weakened the power of selection to weed out mutations leading to intellectual disabilities.
Based on calculations of the frequency with which damaging mutations appear in the human genome and the assumption that 2000 to 5000 genes are required for intellectual ability, Dr. Crabtree estimates that within 3000 years (about 120 generations) we have all sustained two or more mutations harmful to our intellectual or emotional stability.
"Moreover, 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."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," says Dr. Crabtree.
"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."