Aug. 1, 2014 – A study of 1,400 ancient and modern human skulls suggests that a reduction in testosterone hormone levels accompanied the development of cooperation, complex communication and modern culture some 50,000 years ago.
The research, published in today’s issue of the journal Current Anthropology, “uses craniofacial evidence to propose that lowered testosterone levels could explain the relatively sudden origin of modern behavior about 50,000 years ago,” says University of Utah biology graduate student Robert Cieri.
The idea being – to put it as crudely as possible – that lower testosterone would lead to less bashing over the head and more dialogue.
“Humans are uniquely able to communicate complex thoughts and cooperate even with strangers,” Cieri says. “New research on fossilized Stone Age humans from Europe, Africa and the Near East suggests these traits are linked, developed around 50,000 years ago, and were a driving force behind the development of complex culture.”
Homo sapiens, or modern humans, first appeared in the fossil record about 200,000 years ago, but evidence of modern behavior, such as symbolic artifacts and advanced tools are only about 50,000 years old, he adds.
So if that hypothesis is right, lower testosterone made all the good stuff possible – language, chat, jokes; social interaction and co-operation, art, pecan brownies. (Also nuclear weapons, global warming, genocide.)
I’m wondering if they mean lower testosterone in females as well as males or just males.
Patricia Churchland puts hormones at the center of human morality. Lena Groeger wrote up a talk of hers at Massimo Pigliucci’s blog in 2011.
It all begins with me. Ok, not me, but the self. Each one of us is equipped with a neural circuitry that ensures our own self-caring and well-being — values in the most fundamental sense. As Churchland likes to say “we’re all born with systems that are very deep in the values business.” Neurons in the brainstem and hypothalamus monitor the inner state of our bodies to keep us alive; they also cause us to run from predators or eat when we’re hungry. Without these life-relevant feelings we wouldn’t survive very long, let alone reproduce.
The next step is to move from self-caring to other-caring. In mammals, this shift occurs not by some radical new engineering plan, but by slight adjustments to the neural mechanisms that are already in place. Modifications to the emotional, endocrine, stress and reward/punishment systems motivate new values, namely, the well-being of certain others. It’s as if the “golden circle of me” expands to include offspring, mates, friends and eventually even strangers.
At the heart of all these modifications and changes to the brain is a relatively simple hormone called oxytocin. Oxytocin is thought to play an important role in mammalian bonding, evoking feelings of contentment and trust, reducing defensive behaviors like fleeing or fighting, and increasing the sense of calmness and security. Churchland describes the importance of oxytocin by telling her favorite story of all time — it involves voles.Actually, two types of voles: prairie voles and montane voles. Prairie voles bond for life; montane voles are promiscuous. Male prairie voles protect their pups from harm, provide them with food, and fight off other males. Male montane voles take no role in guarding the nest, the female, or the pups. Scatter them across a room, prairie voles will collect back together in a huddle. Montane voles are content to be left alone.What makes these furry little rodents behave so differently? In the 1970’s neuroscientist Sue Carter decided to look for the answer in the brain. She found that in a very specific place, the density for oxytocin receptors was much higher in prairie voles than in montane voles. Subsequent studies have shown that blocking the receptors for oxytocin in prairie voles changes their social behavior dramatically, and they no longer bond with their mates. For Churchland, this story was the clue that oxytocin was the neural mechanism for attachment, or what “Hume might accept as the germ of the moral sentiment.”