Neanderthals Lacked Social Skills

For ages, anthropologists have puzzled over Neanderthal and human brains, since they were the same size. If each species had comparable brainpower, why did humans dominate?

A comparison of Neanderthal and human brains has revealed it was a matter of allocation: Neanderthal brains focused more on vision and movement, leaving less room for cognition related to social networking.

According to the study, published in the journal Proceedings of the Royal Society B, bigger eyed and larger bodied Neanderthals required more brain space devoted to the visual system and basic body functions, leaving less area for what co-author Robin Dunbar called "the smart part."

He explained to Discovery News that this is "the part that is doing the creative thinking."

Dunbar, a professor of evolutionary psychology at the University of Oxford, and colleagues Eiluned Pearce and Chris Stringer compared the skulls of 32 anatomically modern humans and 13 Neanderthals. The skulls date to 27,000 to 75,000 years ago. The researchers noticed that Neanderthals had significantly larger eye sockets.

The researchers next used the known relationship between the height of the eye socket and the size of visual brain areas in living primates to estimate how much of each brain was dedicated to visual processing. Once differences in body and visual system size were taken into account, the researchers could then compare how much of the brain was left over for other types of cognition.

It's clear that environmental differences affected the evolution of each species. The common ancestor of Neanderthals and Homo sapiens was Homo heidelbergensis. It had a bulkier body, as for Neanderthals, but did not possess enlarged eyes.

"The large eyes (of Neanderthals) are purely an adaptation to low light levels, and long dark nights at higher latitudes outside the tropics," Dunbar said.

Neanderthals also tended to be shorter than humans, which again was an adaptation to colder climates since this reduces heat loss through the extremities. Modern Eskimos exhibit some of this adaptation.

Neanderthals in Europe also "developed a very confrontational and dangerous style of hunting, and were very dependent on a heavy meat diet," Dunbar shared. "Modern humans (in Africa) developed the bow and arrow, as well as spear throwers, which allowed hunting at arms' length and often focused on smaller prey."

As for what happened to the Neanderthals, some researchers believe that they were simply absorbed into the modern human population. There is evidence that, as numerous humans migrated north into Europe, they interbred with Neanderthals.

Another theory, supported by this new study, is that Neanderthals went extinct because they were less capable of forming larger social networks. Pearce theorized that "smaller social groups might have made Neanderthals less able to cope with the difficulties of their harsh Eurasian environments because they would have had fewer friends to help them out in times of need."

She continued, "Overall, differences in brain organization and social cognition may go a long way towards explaining why Neanderthals went extinct whereas modern humans survived."

Dunbar further thinks that new diseases brought in by humans could have hurt Neanderthals. He said, "It was clear that, by the end, they were struggling to maintain a foothold in Ice Age Europe, having been squeezed down into the southern appendages of Europe (in places like Spain and Italy)."

Clive Gamble, an expert on the archaeology of human origins and a professor at Southampton University praised the new work, saying, "This paper cracks a big problem in human evolution. Neanderthals had brains as big as ours, yet did not regularly produce the sorts of cultural stuff- art, ornamentation and complicated tools -- that we take for granted...Brains got bigger, but in different ways."

"I've long argued for social differences between Neanderthals and ourselves," Gamble concluded. "It doesn't make us better than them and it doesn't confirm the age-old prejudices about stupid, brutish Neanderthals. What it does do, quite literally, is make us see them with different eyes."

Neanderthal brains focused more on vision and movement, leaving less room for cognition related to social skills.

Back in the Beginning

To put a human face on our ancestors, scientists from the Senckenberg Research Institute used sophisticated methods to form 27 model heads based on tiny bone fragments, teeth and skulls collected from across the globe. The heads are on display for the first time together at the Senckenberg Natural History Museum in Frankfurt, Germany. This model is Sahelanthropus tchadensis, also nicknamed "Toumai," who lived 6.8 million years ago. Parts of its jaw bone and teeth were found nine years ago in the Djurab desert in Chad. It's one of the oldest hominid specimens ever found.

Australopithecus afarensis

With each new discovery, paleoanthropologists have to rewrite the origins of man's ancestors, adding on new branches and tracking when species split. This model was fashioned from pieces of a skull and jaw found among the remains of 17 pre-humans (nine adults, three adolescents and five children) which were discovered in the Afar Region of Ethiopia in 1975. The ape-man species, Australopithecus afarensis, is believed to have lived 3.2 million years ago. Several more bones from this species have been found in Ethiopia, including the famed "Lucy," a nearly complete A. afarensis skeleton found in Hadar.

Australopithecus africanus

Meet "Mrs. Ples," the popular nickname for the most complete skull of an Australopithecus africanus, unearthed in Sterkfontein, South Africa in 1947. It is believed she lived 2.5 million years ago (although the sex of the fossil is not entirely certain). Crystals found on her skull suggest that she died after falling into a chalk pit, which was later filled with sediment. A. africanus has long puzzled scientists because of its massive jaws and teeth, but they now believe the species' skull design was optimal for cracking nuts and seeds.

Paranthropus aethiopicus

The skull of this male adult was found on the western shore of Lake Turkana in Kenya in 1985. The shape of the mouth indicates that he had a strong bite and could chew plants. He is believed to have lived in 2.5 million years ago and is classified as Paranthropus aethiopicus. Much is still unknown about this species because so few reamins of P. aethiopicus have been found.

Paranthropus boisei

Researchers shaped this skull of "Zinj," found in 1959. The adult male lived 1.8 million years ago in the Olduvai Gorge of Tanzania. His scientific name is Paranthropus boisei, though he was originally called Zinjanthropus boisei -- hence the nickname. First discovered by anthropologist Mary Leakey, the well-preserved cranium has a small brain cavity. He would have eaten seeds, plants and roots which he probably dug with sticks or bones.

Homo rudolfensis

This model of a sub-human species -- Homo rudolfensis -- was made from bone fragments found in Koobi Fora, Kenya, in 1972. The adult male is believed to have lived about 1.8 million years ago. He used stone tools and ate meat and plants. H. Rudolfensis' distinctive features include a flatter, broader face and broader postcanine teeth, with more complex crowns and roots. He is also recognized as having a larger cranium than his contemporaries.

Homo ergaster

The almost perfectly preserved skeleton of the "Turkana Boy" is one of the most spectacular discoveries in paleoanthropology. Judging from his anatomy, scientists believe this Homo ergaster was a tall youth about 13 to 15 years old. According to research, the boy died beside a shallow river delta, where he was covered by alluvial sediments. Comparing the shape of the skull and teeth, H. ergaster had a similiar head structure to the Asian Homo erectus.

Homo heidelbergensis

This adult male, Homo heidelbergensis, was discovered in in Sima de los Huesos, Spain in 1993. Judging by the skull and cranium, scientists believe he probably died from a massive infection that caused a facial deformation. The model, shown here, does not include the deformity. This species is believed to be an ancestor of Neanderthals, as seen in the shape of his face. "Miquelon," the nickname of "Atapuerca 5", lived about 500,000 to 350,000 years ago and fossils of this species have been found in Italy, France and Greece.

Homo neanderthalensis

The "Old Man of La Chapelle" was recreated from the skull and jaw of a Homo neanderthalensis male found near La Chapelle-aux-Saints, in France in 1908. He lived 56,000 years ago. His relatively old age, thought to be between 40 to 50 years old, indicates he was well looked after by a clan. The old man's skeleton indicates he suffered from a number of afflictions, including arthritis, and had numerous broken bones. Scientists at first did not realize the age and afflicted state of this specimen when he was first discovered. This led them to incorrectly theorize that male Neanderthals were hunched over when they walked.

Homo floresiensis

The skull and jaw of this female "hobbit" was found in Liang Bua, Flores, Indonesia, in 2003. She was about 1 meter tall (about 3'3") and lived about 18,000 years ago. The discovery of her species, Homo floresiensis, brought into question the belief that Homo sapiens was the only form of mankind for the past 30,000 years. Scientists are still debating whether Homo floresiensis was its own species, or merely a group of diseased modern humans. Evidence is mounting that these small beings were, in fact, a distinct human species.

Homo sapiens

Bones can only tell us so much. Experts often assume or make educated guesses to fill in the gaps in mankind's family tree, and to develop a sense what our ancestors may have looked like. Judging from skull and mandible fragments found in a cave in Israel in 1969, this young female Homo sapien lived between 100,000 and 90,000 years ago. Her bones indicate she was about 20 years old. Her shattered skull was found among the remains of 20 others in a shallow grave.