Sexual selection and its influence on primates brains

Since primate brains and sexual dimorphism are topics that are still fresh on our minds after this morning’s post, I figured I should let you know about a new publication that came out of the open access journal BMC Biology on the differences between male and female primate brain structures and how they developed. It ain’t paleoprimatology in any sense, it’s straight up primtate neuroscience.

In “Primate brain architecture and selection in relation to sex” authors,

Patrik Lindenfors, Charles Nunn and Robert Barton [we wrote about Dr. Barton before, here] examined data on primate brain structures in relation to traits important for male competition, such as greater body mass and larger canine teeth. The researchers also took into account the typical group size of each sex for individual primate species in order to assess sex-specific sociality – the tendency to associate with others and form social groups. The researchers then studied the differences between 21 primate species, which included chimpanzees, gorillas, and rhesus monkeys, using statistical techniques that incorporate evolutionary processes.”

What they found is pretty important, in my opinion. They have concluded that differences between primate sexes cause developmental effects on the brain, and that is due to different pressures on males and females to keep up with social or competitive demands. From,

“The authors found that sexual selection had an important influence on primates brains. Greater male-on-male competition (sexual selection) correlated with several brain structures involved with autonomic functions, sensory-motor skills and aggression. Where sexual selection played a greater role the septum was smaller, and therefore potentially exercised less control over aggression.

In contrast, the average number of females in a social group correlates with the relative size of the telencephalon (or cerebrum), the largest part of the brain. The telencephalon includes the neocortex, which is responsible for higher functions such as sensory perception, generation of motor commands and spatial reasoning. Primates with the most sociable females evolved a larger neocortex, suggesting that female social skills may yield the biggest brains for the species as a whole. Social demands on females and competitive demands on males require skills handled by different brain components, the authors suggest. The contrasting brain types, a result of behavioural differences between the sexes, might be a factor in other branches of mammalian brain evolution beyond anthropoid primates, too.”

I’ve bolded the conclusions that I consider the most impacting. While, I’m weary about the how this applies to humans, I cannot deny the correlations the authors have derived. Research like this is fundamental to understanding the physical origin of very complicated social behaviors, and the authors provide us with a map of primate brains and how they correlate to sex related behaviors.

As far as how this impacts humanity — I believe human brain development is much more complex and social issues and culture imprint human brain development to a much greater degree in humans as compared to non human primates. So it’s a bit hard to say, in my opinion again, that this model of sex-selection and number of females really impact the developments of our brains.

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