A Stanford geneticist, Gerald Crabtree, has concluded that we humans have so many genetic mutations that it has effected our overall intelligence.
Our ancestors were basically smarter than we are today as a result. He suggests that with each generation comes harmful mutations that, down the
line, has impaired our intelligence compared to that of our ancestors. He calculates that within 3,000 years, “we have all sustained two or more
mutations harmful to our intellectual or emotional stability.”
“There is a general feeling that evolution constantly improves us, but it only does that if there is selection applied,” Crabtree said in an
interview. “In this case, it is questionable about how much selection is occurring now compared to the process of optimizing those genes, which
occurred in the jungles of Africa 500,000 years ago.”
Some argue that this point is flawed due to natural selection. Other scientist that disagree have said:
Natural selection is incredibly powerful, and it definitely has the ability to weed out new mutations that significantly impair intellectual ability.
Or does it?
An example he uses to counter this is our sense of smell. Our olfactory receptors have been tuned way down from when we hung out in caves 500,000
years ago. Our sniffer kept us alive and put food in our bellies. As compared to a dog's sense of smell, we've damn near lost most of ours because
we don't use it like our ancestors did. We are guided by our intellect now (where did the food come from, what plant/animal, how does it grow, etc)
instead of our pure sense of smell.
“Once you place pressure on intellectual abilities, and take it off of olfactory abilities, the olfactory genes deteriorate,” Crabtree said.
He also believes evolution now selects for other traits--namely, the most healthy and the most immune, not the most intelligent. "Human movement into
communities and cities increased the spread of infectious diseases, and those with the strongest physical constitutions survived to pass on their
So in there lies the rub. Have we really gone through so much negative gene mutation in our brains that our intellect has been stymied? Because the
"dumber" physically strong survived in the past under harsh conditions, with us being the product of their survival, does it mean we are getting
dumber down the line of human evolution? Something to think about...