David Linden presents paradox: human brain evolved and primitive

Linden presents paradox: human brain evolved and primitive
October 30, 2009

By Sara Jenks
Writer

The human brain is certainly different than the rest of the animal kingdom--but humans are the weird ones, said David Linden's in his talk entitled "Love, Sex and Brain Evolution."

The professor of neuroscience from the Johns Hopkins University School of Medicine illustrated his point with human's unique approach to mating.  Linden used blunt humor to emphasize his point asking the audience, "What is your cat thinking about while you are having sex?  He thinks you are crazy."

The filled LC Forum howled as he continued, "Your cat is revolted that you mate when the woman is not ovulating and everyone knows you're supposed to have sex in public.  Your child is five years old and still can't take care of herself - what a loser!"

Linden compared the brain architecture to an ice cream cone. Each additional scoop of ice cream piled on a pre-existing scoop represents evolved brain mechanisms that are still connected to older, more primitive aspects.   Humans and rats share identical parts of the brain--the "older scoops"--but throughout evolutionary history humans have added more complex material.  This addition of many inefficient neurons made for a very clever being, albeit with an "ill-engineered system."  

Humans have become one of few species to develop pair bonds between mating partners.  Unlike other animals, female humans do not overtly display ovulation with signs such as emitting a certain odor.  The human child endures the longest maturation period of any animal, because of the complex nature of the human brain.  Each of these points represents a unique aspect of our "highly evolved" species, and could not have developed without the ice cream cone nature of brain evolution.

Linden also weighed in on the nature-nurture debate regarding homosexuality.  Given evidence from twin studies and brain scans, Linden concluded that "at least some part of sexual orientation is genetic."  On the other hand he said, "Causality in the brain is a two-way street."  Certain genes influence human activity at any given time, but experience influences brain development, especially during humans' long maturation period.

Throughout the talk Linden demonstrated that humans are not entirely unique in their mating patterns or homosexual tendencies, but the evolutionary reasons for doing so are indeed unique. 

"It was refreshing to hear such taboo topics discussed in such an intellectual yet entertaining manner and the points he raised certainly gave me quite a lot of insight into how much biology and evolution take part in love and sex which I have come to find exceptionally remarkable," said Erica Austin '10.