Humans and Bonobos: Violence and a Thyroid Hormone

Following on something I mentioned in my last post, that the American people (all societies, really) are growing in morality, there is a new study supporting this presupposition that is worth examining. There I pointed back to a 2012 post featuring the work of Steven Pinker, who has influenced me greatly in this matter. In the recent study, published in the journal Nature and reported by the AP:

As a group, mammals average a lethal violence rate against their own of about three killings of their own species in 1,000 deaths. The “root” violence rate of early humans and many of our closer primate cousins is about 20 in 1,000… But in the medieval period, between 700 and 1500 A.D., that deadly rate shot up to about 120 per 1,000.

On average, modern humans now kill each on a rate of 13 in 1,000, Gomez said, basing his calculations on World Health Organization data. But he says the exact numbers are rough and depend on many technical variables, so what is more accurate is to say “violence has decreased significantly in the contemporary age.”

“It seems that we are in the present time less violent than we were in the past,” Gomez said in an email interview.

Looking at the evolutionary tree, they note that “the large grouping called Euarchonta that includes us, other primates, tree shrews and flying lemurs has a rate of about 23 per 1,000” and “It drops to about 18 for great apes.”

That means we might also be the most peaceful of our local evolutionary cousins. Or perhaps not. They didn’t mention Bonobos, aka the “hippy chimps.” According to LiveScience, these guys and gals have a high level of a thyroid hormone (T3) that helps keep aggression in check.

In the below Scientific American article, it is noted that “Juvenile bonobos are incurably playful and like to make funny faces, sometimes in long solitary pantomimes and at other times while tickling one another. Bonobos are, however, more controlled in expressing their emotions–whether it be joy, sorrow, excitement or anger–than are the extroverted chimpanzees.” They are incurably playful but emotionally controlled, an amazing combination, and one no doubt many humans could benefit from emulating.

According to a Phys.rog article from 2011:

Humans share 98.7 percent of our DNA with chimpanzees, but we share one important similarity with one species of chimp, the common chimpanzee, that we don’t share with the other, the bonobo. That similarity is violence. While humans and the common chimpanzee wage war and kill each other, bonobos do not. “There has never been a recorded case in captivity or in the wild of a bonobo killing another bonobo,” notes anthropologist Brian Hare.

This raises not only important moral questions about what we are capable of as a species, but also societal questions about dealing with people who are immoral and have depressed thyroid hormones. Or, for that matter, any number of hormones and/or neurotransmitters seen to be important in our lives as healthy, functioning members of society. It may help us better understand those people and thus feel deeper compassion for them rather than labeling them and casting them out. Studies like this may also help identify physical sources of immoral activity (and/or uncontrolled emotions) in humans to aid in treatment and understanding.

Read more about “Bonobos, Chimpanzees, and Nasty, Peaceful Humans” at WIRED and “Bonobo Sex and Society” at Scientific American.