As part of the Brain Science Institute’s (BSI) Brain Night speaker series, David Linden of the Department of Neuroscience spoke about “Love, Sex and Brain Evolution” to a packed audience in the Bloomberg auditorium last Wednesday.
The sexual behavior that many people think of as the most conventional — monogamous, heterosexual sex — is actually the most unusual when compared to the rest of the animal kingdom. Linden proposed that our aberrant sexual behavior could be simply explained by the fact that neurons are not very good at their jobs.
“Neurons, as information processors, suck,” Linden said. Neurons transmit signals slowly, have a limited signaling range and are unreliable — excited neurons don’t always successfully release neurotransmitters.
Part of this inefficiency is the by-product of evolution. “The brain is built like an ice cream cone,” Linden said. “The brain is never entirely redesigned from the ground up; it tends to add new systems to existing ones.”
He likened the evolution of the human brain from more primitive systems to building a racecar out of parts from a Model T Ford.
“So how do we build clever us out of such suboptimal parts?” Linden asked.
The secret turns out to be quantity. The average human brain has 200 billion neurons, and each neuron makes 5,000 connections to other neurons. The brain of a human newborn is about the same size as that of an adult chimpanzee’s — its large size accounts for the almost uniquely human phenomenon of mother mortality during childbirth. Our large and complex brains mature very slowly; humans have by far the longest childhood in the animal kingdom.
According to Linden, if human neurons weren’t so bad at their jobs, we wouldn’t need such big brains. Humans would not have evolved to have such long childhoods or to pair-bond to ensure that both parents provide for their offspring.
The second part of the lectures focused on the science behind love.
One group of researchers found that, out of 160 cultures surveyed, 147 had very similar descriptions of falling in love, including giddiness, loss of appetite and distortion of judgment.
Across all cultures, brain scans of people who have just fallen in love show similar patterns of activity. Scientists found increased activation in regions that are central to pleasure perception and that are also stimulated by drugs. In the same people, the regions involved in impulse control and social cognition are deactivated.
Interestingly, these are the same brain activity patterns that are detected during orgasm.
Linden admitted neuroscience could be a blunt instrument in studying human sexuality, but at least we now know that when Ke$ha tells us, “Your love is my drug,” she’s got science backing her up.
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