Following
my somewhat vague speculations in my last post, I found several articles
discussing emerging research in behavioral genetics about the significance of
sex hormones in affecting thyroid development and contributing to notable
behavioral differences between sexes.
There is also speculation that such neurochemical differences may also
exist in the brains of other gendered individuals, though experimental evidence
of this is currently lacking.
In
this particular article, a key difference in the role of the thyroid hormones
Triiodthyronin (T3) and Thyroxin (T4) was found to play a role in several behavioral
differences between male and females in the closest relatives to humans;
chimpanzees and bonobos. While chimpanzees
and bonobos experience a similar setting and behavioral patterns early in life,
in adulthood differences in thyroid hormones indicate the role the thyroid
plays in regulating behavior. The major
difference between bonobos, chimpanzees, and humans is that bonobos continue to
have high levels of thyroid hormones after puberty, where instead chimpanzees
and humans both experience a reduction in hormone levels.
As
a result of elevated levels of hormones in adulthood: “Male bonobos are less aggressive, engage in
lasting friendships with females and receive life-long support from their
mothers. In contrast, the social network of male chimpanzees consists of a
mixture of male-male cooperation and aggressive behavioural [sic] strategies in
males that aim on gaining and maintaining high social status. The consequence is that the two sister
species live in different social systems.”
Further, male bonobos were found to have even higher thyroid levels than females, and that female bonobos preferred “thyroid hormone ‘doped’ mates.” Speculating from my own knowledge, It is perhaps possible to speculate then that trends in natural selection differ between bonobos, chimpanzees, and humans (since it plays a role in mate selection). Therefore, trends of male dominance are genetically selected by the process of evolution in humans and chimpanzees.
I
would further speculate that even though non-humans arguably do not possess
metacognition, as humans do, the role of metacognition is likely offset
significantly by neurochemistry and the role of the unconscious. Take for example, the thyroid’s known
influence on attention deficit hyperactivity disorder (ADHD), and the vital
role psychotropic medicine plays in moderating ADHD.
Sources:
Bonobos Stay Young Longer
Behavioral Issues with Thyroiditis
Sources:
Bonobos Stay Young Longer
Behavioral Issues with Thyroiditis
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