December 30, 2004
Are C-Sections Evolutionarily Favored?
In a copyrighted story in the Dec. 29 Chicago Tribune (free subscription required), science reporter Ronald Kotulak reports ("Study charts expansion of human brain"):
The first study of genes that build and operate the brain shows that humans underwent a unique period of rapid brain expansion that endowed them with a special form of intelligence not shared by any other animal, according to University of Chicago researchers.
The colossal leap forward grew the human brain to three or four times the size of that of a chimpanzee--man's closest genetic relative--when body sizes are equalized. That vast computing power pushed human intelligence over the threshold of basic instincts and into an unparalleled realm of cognition, self-awareness and consciousness.
Brain size, therefore, appears to have given humans the evolutionary edge over our genetic near-relations. Is there any limit to the advantage brain size confers on our species? Not after the development of the C-section:
Brain size was thought to have hit its maximum because a larger skull would not be able to squeeze through the birth canal. But Caesarean sections--the practice of surgically removing a baby from the womb--could eliminate those limitations, [Univ. of Chicago geneticist Bruce] Lahn noted.
"With the C-section, we have just lifted a huge barrier to how big the brain can be," he said. "I wouldn't be surprised if in a few hundred years C-sections [account for] almost 100 percent [of births]."
December 30, 2004 | Permalink