In a paper published in the journal Current Anthropology, a team of researchers funded by The Leakey Foundation explore the biological basis of the technology boom and expansion of culture that happened 50,000 years ago.
DURHAM, N.C. -- Modern humans appear in the fossil record about 200,000 years ago, but it was only about 50,000 years ago that making art and advanced tools became widespread.
A new study appearing Aug. 1 in the journal Current Anthropology finds that human skulls changed in ways that indicate a lowering of testosterone levels at around the same time that culture was blossoming.
"The modern human behaviors of technological innovation, making art and rapid cultural exchange probably came at the same time that we developed a more cooperative temperament," said lead author Robert Cieri, a biology graduate student at the University of Utah who began this work as a senior at Duke University.
Credit: Robert Cieri, University of Utah
The study, which is based on measurements of more than 1,400 ancient and modern skulls, makes the argument that human society advanced when people started being nicer to each other, which entails having a little less testosterone in action.
Heavy brows were out, rounder heads were in, and those changes can be traced directly to testosterone levels acting on the skeleton, according to Duke anthropologist Steven Churchill, who supervised Cieri's work on a senior honors thesis that grew to become this 24-page journal article three years later.
What they can't tell from the bones is whether these humans had less testosterone in circulation, or fewer receptors for the hormone.
The research team also included Duke animal cognition researchers Brian Hare and Jingzhi Tan, who say this argument is in line with what has been established in non-human species. In a classic study of Siberian foxes, animals that were less wary and less aggressive toward humans took on a different, more juvenile appearance and behavior after several generations of selective breeding.
"If we're seeing a process that leads to these changes in other animals, it might help explain who we are and how we got to be this way," said Hare, who also studies differences between our closest ape relatives -- aggressive chimpanzees and mellow, free-loving bonobos.
Those two apes develop differently, Hare said, and they respond to social stress differently. Chimpanzee males experience a strong rise in testosterone during puberty, but bonobos do not. When stressed, the bonobos don't produce more testosterone, as chimps do, but they do produce more cortisol, the stress hormone.Their social interactions are profoundly different and, relevant to this finding, their faces are different, too. "It's very hard to find a brow-ridge in a bonobo," Hare said.
Craniofacial feminization in Homo sapiens. The 110-90 Ka year old male specimen Skhul 5 (left) in lateral (top) and frontal (bottom) views, compared to that of a recent African male (right), showing the large brow ridges and long and narrow, masculinized face characteristic of MSA/MP-associated modern humans. Both specimens have been scaled to the same nasion-bregma height and aligned on those landmarks. Photo credit- David Brill, used with permission. From Craniofacial Feminization, Social Tolerance, and the Origins of Behavioral Modernity by Cieri et al.
Cieri compared the brow ridge, facial shape and interior volume of 13 modern human skulls older than 80,000 years, 41 skulls from 10,000 to 38,000 years ago, and a global sample of 1,367 20th century skulls from 30 different ethnic populations.The trend that emerged was toward a reduction in the brow ridge and a shortening of the upper face, traits which generally reflect a reduction in the action of testosterone.
There are a lot of theories about why, after 150,000 years of existence, humans suddenly leapt forward in technology. Around 50,000 years ago, there is widespread evidence of producing bone and antler tools, heat-treated and flaked flint, projectile weapons, grindstones, fishing and birding equipment and a command of fire. Was this driven by a brain mutation, cooked foods, the advent of language or just population density?
The Duke study argues that living together and cooperating put a premium on agreeableness and lowered aggression and that, in turn, led to changed faces and more cultural exchange. "If prehistoric people began living closer together and passing down new technologies, they'd have to be tolerant of each other," Cieri said. "The key to our success is the ability to cooperate and get along and learn from one another."
This article is a news release from the Duke University Office of News and Communications.
Work funded by The Leakey Foundation, NSF, and the University of Iowa Orthodontics Department.
Video on Today: A Canadian woman was diagnosed with a stroke after she filmed herself suffering the symptoms, and posted it online. Doctors previously insisted she was just stressed. NBC’s Anne Thompson reports.
You’ve heard it from us before. The Quiet Revolution is happening. Freelancers are moving away from consumption and towards connection and becoming more conscious about what their purchases mean for themselves and their neighbors. They’re also spending more of their time volunteering in their local communities. And, as it turns out, this doesn’t just benefit their neighbors, but their physical and mental health as well. Indeed, a new study by the UnitedHealth Group, the Optimum Institute, and Mashable has found a link between volunteering and better physical, mental, and emotional health. Here are some of the more interesting findings: 78% said that volunteering ...
Atoms of a new super-heavy element the as-yet-unnamed element 117 have reportedly been created by scientists in Germany, moving it closer to being officially recognized as part of the standard periodic table
CAIRO, April 28 (Reuters) - Remains of about 50 mummies, including newborn babies, thought to belong to the 18th Pharaonic dynasty were found in a huge tomb in Egypt's Valley of the Kings in Luxor, Antiquities Minister Mohamed Ibrahim said on Monday.
At the dawn of rapid prototyping, a common predication was that 3D printing would transform manufacturing, spurring a consumer revolution that would put a printer in every home. That hasn't quite happened---and like so many emerging technologies, rapid prototyping has found its foothold in a surprisingly different field: Medicine.
Your Bike Helmet: More Than an Accessory, Bike helmet safety guidelines for children and adults. How to fit a bike helmet. As in all aspects of safety, bike helmets are a situation where we should lead by example. Here are a few tips for choosing and fitting helmets for adults and children alike. Safety
Natalia Corres's insight:
Summer Summer Summer - please be safe as it gets to be prime biking weather!
Researchers for the first time have created microbes containing artificial DNA, expanding the universal genetic code that guides life. The advance one day could lead to new antibiotics, vaccines and other medical products.
Sharing your scoops to your social media accounts is a must to distribute your curated content. Not only will it drive traffic and leads through your content, but it will help show your expertise with your followers.
How to integrate my topics' content to my website?
Integrating your curated content to your website or blog will allow you to increase your website visitors’ engagement, boost SEO and acquire new visitors. By redirecting your social media traffic to your website, Scoop.it will also help you generate more qualified traffic and leads from your curation work.
Distributing your curated content through a newsletter is a great way to nurture and engage your email subscribers will developing your traffic and visibility.
Creating engaging newsletters with your curated content is really easy.