-- Robert Preidt
FRIDAY, Nov. 16 (HealthDay News) -- The human race is slowly
losing its intellectual and emotional capabilities because it no
longer faces extreme evolutionary pressures, new research
Human intelligence and behavior require optimal functioning of a
large number of genes, but the intricate web of genes that gives
people these capabilities has started to backslide, the scientists
said in an article appearing Nov. 12 in the journal
Trends in Genetics.
"The development of our intellectual abilities and the optimization of thousands of intelligence genes probably occurred in relatively nonverbal, dispersed groups of peoples before our ancestors emerged from Africa," study author Dr. Gerald Crabtree, of Stanford University, said in a journal news release.
In the early stages of human evolution, intelligence was
critical for survival and there was immense selective pressure
acting on the genes required for intellectual development. But once
humans achieved a certain level of evolutionary progress, they
slowly began to lose ground.
The development of agriculture led to urbanization, which may
have weakened the power of natural selection to eliminate mutations
that caused intellectual disabilities, the researchers
Based on the frequency that harmful mutations appear in the
human genome and the assumption that 2,000 to 5,000 genes are
required for intellectual ability, Crabtree estimated the effect
that the past 3,000 years (about 120 generations) of human history
have had on humans. He concluded that all people now carry two or
more mutations harmful to their intellectual or emotional
He noted, however, that the loss of intellectual and emotional
capabilities is quite slow and it's likely that a solution will be
found in the future.
"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," Crabtree said.
"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," he said. "Thus, the brutish process of natural selection will be unnecessary."
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