Posts Tagged ‘Anthropology’

Sheer Numbers Gave Early Humans Edge Over Neanderthals

29 Jul

By Kate Shaw, Ars Technica

Between 35,000 and 45,000 years ago, Neanderthals in Europe and Asia were replaced by the first modern humans. Why and how this transition occurred remains somewhat controversial. New research from the journal Science suggests that sheer numbers may have played a large role in modern humans’ eventual takeover; archeological data shows that early populations of modern humans may have outnumbered Neanderthals by more than 9 to 1.

Two archaeologists from Cambridge University analyzed data from the Aquitaine region of southern France, which has Europe’s highest density of sites from this era, and one of the most complete archeological records. They used data from three time periods that encompassed the transition between Neanderthals and modern humans: the Mouterian and Chatelperronian eras, during which Neanderthals lived, and the Aurignacian period, which was dominated by modern humans. By examining differences between land use during these time periods, the researchers hoped to determine whether population dynamics played a role in the transition between these two hominins.

Because of the difficulties in estimating long-ago populations, the researchers used a few different proxies for population sizes and densities. They analyzed the number of occupied sites in each era, the size of these sites, and the accumulation rates of stone tools and animal food remains. Through these proxies, the researchers could get good estimates of population dynamics during the transition from Neanderthals to modern humans in Aquitaine.

From the Mouterian to the Chatelperronian era, there was very little increase in the number of rock-shelter sites. There were about 26 sites occupied in the Mouterian era, and 31 in the Chatelperronian period, suggesting that the Neanderthal population was not growing quickly. However, there were about 108 sites occupied by modern humans in the Aurignacian period. The increase is similar for occupied open-air sites. Adjusted for time scales, these figures suggest that, between the last Neanderthal-dominated era and the first era dominated by modern humans, the population numbers and densities increased by a factor of about 2.5.

A similar trend was seen in the sizes of occupied areas, with the Neanderthal sites averaging less than 200 square meters, while several of the modern human sites reached up to 600 square meters. From the size differences of the sites, the researchers estimate population increased up to 3 times as the Neanderthal-dominated era ended and modern humans occupied their sites.

Finally, the accumulation of stone tools and animal remains tells a similar story: modern humans were far more numerous than the Neanderthals they replaced. The densities of stone tools and animal food remains skyrocketed between the Chatelperronian and Aurignacian eras—according to these differences, the modern human population probably outnumbered the Neanderthals by a factor of about 1.8.

Each of these statistics, taken alone, tells only part of the story. Since these archaeological proxies was developed independently, the estimations can be looked at cumulatively to get a better idea of the different population sizes. When evaluated as a whole, these estimations show that the population size and densities of modern humans may have been more than 9 times those of the Neanderthals around the time of the population’s transition. It’s very likely that a numerical advantage that large played a significant role in modern humans’ dominance over their earlier counterparts.

While the study did not directly address the features that gave modern humans a population advantage, the authors suggest that it was probably due to a combination of factors such as improved food storage, an increase in social cohesion, and the potential for trade and the exchange of goods.

Source: Ars Technica

Image: A comparison of Neanderthal and human settlement density and size about 30,000 years ago. (Science)

See Also:

Citation: Science, 2011. DOI: 10.1126/science.1206930


How did humans really evolve? [Io9 Backgrounder]

04 Mar
Almost two million years ago, a band of brave explorers left their families behind in their warm, tropical home and sought refuge in northern lands. Armed with sharp stone tools and their wits, they followed the coast as far north as they could, then began to veer east, settling on the sunny, fertile shores of an inland sea that today we call the Mediterranean. Their children spread further north and east, and a million years later they had established settlements along the coasts of today's Europe, England, and China. More »

Humans’ treatment of other animals shaped our evolution [Evolution]

22 Jul
Humans are one of the few animals that adopts and cares for other animals. Our cross-species connections might be older and more important than we ever imagined, driving human evolution for millions of years and even helping us invent language. More »

‘Lucy’s Grandfather’ Fossil Makes Humanity’s Ancestor Seem More Like Us

22 Jun

A 3.6 million-year-old fossil from one of humanity’s earliest ancestors is more human-like than expected — and much taller.

The discovery makes Lucy, the best-known fossil of all, appear to be exceptionally short by comparison. Lucy and the new skeleton are both Australopithecus afarensis, the first fully bipedal primate and a direct ancestor of humanity. Unlike Lucy and every other A. afarensis fossil, the new skeleton has complete forelimb and hindlimb bones, allowing researchers to estimate its size more accurately.

The new A. afarensis specimen stood between 5 and 5 1/2 feet tall, towering over Lucy’s 3-foot height. Other fossil fragments suggested that Lucy was an unreliable measuring stick for A. afarensis, but the new fossil is the most conclusive evidence yet. Dubbed “Kadanuumuu,” or Big Man, it is described June 21 in the Proceedings of the National Academy of Sciences.

Big Man’s limbs also appear well-suited for running, in contrast to the shortened gait implied by Lucy’s skeleton. The proportions compare to those found two million years later in Homo erectus, and would not be out of place in a modern human, said study co-author Owen Lovejoy, a Kent State University paleoanthropologist.

“The difference between Australopithecus and humans is much less than everyone expected,” said Lovejoy. “Upright walking and running were pretty advanced at 3.6 million years ago, and they didn’t change much over the next two million years. Most of the changes in that period of time took place elsewhere.”

Lovejoy was also part of the team that discovered Ardipithecus ramidus, a 4.4 million-year-old possible human ancestor that was officially described last October. Ardipithecus was far less chimp-like than expected.

That raises the possibility that it’s the other Great Apes, rather than humans, whose bodies have evolved the most over the last few million years.

Big Man, with a rib cage shaped more like our own than that of a chimpanzee or gorilla, reinforces that notion.

“Chimps and gorillas are again the unusual form. Hominids and ourselves bear many primitive traits that haven’t been specialized like they have in gorillas,” said Lovejoy.

“The classic cartoon of the ape turning into the human doesn’t work at all.”

Image: Yohannes Haile-Selassie/PNAS.

See Also:

Citation: “An early Australopithecus afarensis postcranium from Woranso-Mille, Ethiopia.” By
Yohannes Haile-Selassie, Bruce M. Latimer, Mulugeta Alene, Alan L. Deino, Luis Gibert, Stephanie M. Melillo, Beverly Z. Saylor, Gary R. Scott, C. Owen Lovejoy.

Brandon Keim’s Twitter stream and reportorial outtakes; Wired Science on Twitter. Brandon is currently working on a book about ecological tipping points.