by: Sherry Baker
Have you ever wondered – and maybe even said out loud – why so many people seem downright dumb? According to a hypothesis just published in the Cell Press journal Trends in Genetics, maybe humans are becoming less intelligent.
The paper’s author, Dr. Gerald Crabtree, of Stanford University, suggests we are losing our intellectual and emotional capabilities because the intricate web of genes giving Homo sapiens our supposedly superior-to-other-animals’ brain power is susceptible to dumbing down mutations.
Dr. Crabtree points out that human intelligence and behavior require the optimal functioning of a large number of genes. And these genes need enormous evolutionary pressures to be maintained. “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,” Dr. Crabtree said in a media statement. He explained that in this ancient environment, intelligence was critical for survival so genes required for intellectual development were maintained and favored, resulting in a growth of human intelligence.
The supposed problem is that as agriculture developed and then urbanization, there was less natural selection of the most intelligent. Mutations weren’t weeded out as often and that led to more intellectual disabilities. In addition, Dr. Crabtree points out, recent neuroscience findings suggest genes involved in brain function are especially susceptible to mutations.
Dr. Crabtree predicts, based on calculations of the frequency with which harmful mutations appear in the human genome and the assumption that 2,000 to 5,000 genes are required for intellectual ability, that within about 120 generations, humans will have sustained two or more harmful mutations to our intellectual and/or emotional stability. Dr. Crabtree argues that the combination of less selective pressure combined with the large number of somewhat easily mutated genes is eroding our intellectual and emotional capabilities.
This brings up the question of whether humans are actually “devolving” instead of continuing to evolve. Those who follow research showing the potential damage to the human body — including the brain — from pesticides, BPA and other chemicals we are now bombarded with might well wonder if environmental factors could be literally dumbing down huge numbers of people at the present time, too.
Dr. Crabtree doesn’t seem too worried about humans possibly growing dumber, for whatever reasons. He assumes future technologies are will be able to “fix” the problem through science and medicine. “I think we will know each of the millions of human mutations that can compromise our intellectual function and how each of these mutations interacts with each other and other processes as well as environmental influences,” Dr. Crabtree said in the media statement. “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.”