If it weren’t for environmental toxins, we’d be apes

A fascinating study is described in the NYT Science Section today (here). Researchers are suggesting that a gene mutation may well be responsible for the evolution of the human brain. The Times reports:

2.4 million years ago, a muscle gene underwent a disabling alteration. … This could have made all the difference, leading to the enlarged brains of the lineage that evolved into modern humans. Researchers who made the discovery said this might be the first recognized functional genetic difference between humans and the apes that can be correlated with anatomical changes in the fossil record. As they said, the gene mutation may represent the beginning of the ancestral triumph of brain over brawn.
At the least, scientists said, the small mutated gene probably accounts for the more graceful human jaw, in contrast to the protruding ape jaw and facial ridges.

Why the mutation? The following speculation is offered:

The cause of the mutation was unknown and probably unknowable: damage from cosmic rays perhaps, ingested toxins or other environmental exposures. Other contemporary hominid species could have been exposed to the same conditions, but for some reason, escaped with their myosin gene unaltered — and their jaws as formidable as ever. These robust but small-brain species continued to live in Africa until their line became extinct about one million years ago.

Dr. Minugh-Purvis said it was unclear how the mutation could have become fixed in the species, considering its potentially deleterious effects on survival. Perhaps other agents of change were already at work, like the transition to a richer protein diet of meat. The heavier jaws were required for grinding the mainstays, nuts and plants, in their diets.

So, those whose gene remained unaltered were slated to become extinct, while lucky us, what with environmental toxins and our desire to keep grinding on those nuts and plants (early stages of Nighttime Eating Syndrome, see post yesterday), we get the better brain and a nicer jaw line. I’m going home to remove my lawn sign condemning the use of chemical lawn care products. I don’t want to be remembered as standing in the way of further evolutionary development.