How we tamed ourselves and became modern?

Call a man "tame" or "domesticated" and he's not likely to take it as a compliment. But all of us, male and female, may have to get used to it: At a high-level meeting earlier this month, scientists argued that "self-domestication" was a key process in the evolution of our species. They noted that with our reduced jaws, flat faces, and lower male aggression, humans are to chimps as dogs are to wolves, showing many of the physical traits that emerge during animal domestication. 

Big brow ridges and teeth suggest that ancient Homo heidelbergensis(above) may have had more testosterone than modern Homo sapiens (left).

The accompanying changes in behavior, especially among men, might have helped humans evolve more complex language, live atop each other in cities, and work together to create sophisticated cultures.

No one set out to domesticate humans, of course. But at the first-ever symposium on self-domestication of humans, held at the Salk Institute for Biological Studies, researchers outlined a set of linked behavioral and anatomical changes seen both in animals that humans have tamed and in creatures that have tamed themselves, such as bonobos.

Cave Paintings in Indonesia Redraw Picture of Earliest Art

The dating discovery recasts ancient cave art as a continent-spanning human practice.

The art shown here has not been dated, but is stylistically similar to other art in the area now found to be around 40,000 years old.

A hand painted in an Indonesian cave dates to at least 39,900 years ago, making it among the oldest such images in the world, archaeologists reported in a study that rewrites the history of art.

The discovery on the island of Sulawesi vastly expands the geography of the first cave artists, who were long thought to have appeared in prehistoric Europe around that time. Reported in the journal Nature, the cave art includes stencils of hands and a painting of a babirusa, or "pig-deer," which may be the world's oldest figurative art. 

"Overwhelmingly depicted in Europe and Sulawesi were large, and often dangerous, mammal species that possibly played major roles in the belief systems of these people," says archaeologist and study leader Maxime Aubertof Griffith University in Queensland, Australia. 

The finds from the Maros cave sites on Sulawesi raise the possibility that such art predates the exodus of modern humans from Africa 60,000 or more years ago.

"I predict that even older examples of cave art will be discovered on Sulawesi, and in mainland Asia, and ultimately in our African homeland," says human origins expert Chris Stringer of the Natural History Museum in London, who was not on the study team.

The oldest dated hand stencil in the world and possibly the oldest figurative depiction in cave art— a pig-deer)—were found in Leang Timpuseng cave in Sulawesi. 

Rapid expansion of human

Model of human brain

A new study could rewrite the story of ape and human brain evolution. While the neocortex of the brain has been called "the crowning achievement of evolution and the biological substrate of human mental prowess," newly reported evolutionary rate comparisons show that the cerebellum expanded up to six times faster than anticipated throughout the evolution of apes, including humans.

The findings suggest that technical intelligence was likely at least as important as social intelligence in human cognitive evolution, the researchers say.

"Our results highlight a previously unappreciated role of the cerebellum in ape and human brain evolution that has the potential to refocus researchers' thinking about how and why the brains in these species have become distinct and to shift attention away from an almost exclusive focus on the neocortex as the seat of our humanity," says Robert Barton of Durham University in the United Kingdom.

"In humans, the cerebellum contains about 70 billion neurons -- four times more than in the neocortex," Barton says. "Nobody really knows what all these neurons are for, but they must be doing something important."

The neocortex had gotten most of the attention in part because it is such a large structure to begin with. As a result, in looking at variation in the size of various brain regions, the neocortex appeared to show the most expansion. But much of that increase in size could be explained away by the size of the animal as a whole. Sperm whales have a neocortex that is proportionally larger than that of humans, for example.

Barton and Venditti say that the cerebellum seems to be particularly involved in the temporal organization of complex behavioral sequences, such as those involved in making and using tools, for instance. Interestingly, evidence is now emerging for a critical role of the cerebellum in language, too.

While plenty of work remains, the new study establishes the cerebellum as "a new frontier for investigations into the neural basis of advanced cognitive abilities," the researchers say.

Humanity Has More Mothers Than Fathers, DNA Reveals

Mothers outnumbered fathers throughout much of human history, a new DNA analysis of people around the world shows. The genetic findings offer evidence for polygyny, when one man has many wives, and other reproductive customs, as people migrated out of Africa.

"Historically more of the women were reproducing than the men," study researcher Mark Stoneking, a professor of biological anthropology at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, said. "This often happens in human societies, because not all men are able to afford wives, or sometimes a few men will have many wives." These practices resulted in females making a larger genetic contribution to the global population than males did, the researchers found.

Stoneking and colleagues used a new method to scrutinize genetic variation within the male Y-chromosome. By looking at one part of the Y chromosome, they found all of the genetic variants, or slight differences in the order of DNA's "letters," within that region.

Credit: razlomov | Shutterstock

He and his colleagues put their new technique to work on DNA samples of 623 males from 51 populations around the world, including Australian, European, and American populations. The new method allowed them to take the DNA samples from each male and compare the paternally inherited Y chromosome (NRY), which gets passed down from father to son, with mitochondrial DNA (mtDNA), which mothers pass down to their children, Stoneking said.

Women likely traveled for marriages, leaving their hometowns and moving in with their husbands, the genetic analysis showed. So, females migrated more than males did, spreading their female mitochondrial DNA far and wide and reducing genetic variability between populations. Men, in contrast, tended to stay put, which resulted in their sons having distinct genes in each population.

On a regional scale, the DNA samples showed a detailed story. For example, people in East Asia and Europe have larger genetic differences for paternal than for maternal DNA, suggesting high levels of female migration. In contrast, populations in Africa, Oceania and the Americas have bigger differences for maternal DNA than for paternal DNA.

Via LiveScience: http://www.livescience.com/47976-more-mothers-in-human-history.html
Full article in Investigative Genetics: http://www.investigativegenetics.com/content/5/1/13