How Do Paleoanthropologists Know That Acheulian Hand Axes Were Used To Butcher Animals?

Humans Shaped Stone Axes 1.viii One thousand thousand Years Ago, Report Says

Testify Pushes Advanced Tool-Making Methods Back in Fourth dimension

9/1/eleven

A new study suggests that Homo erectus, a forerunner to modernistic humans, was using avant-garde tool-making methods in Eastward Africa 1.8 million years ago, at to the lowest degree 300,000 years earlier than previously thought. The written report, published this week in Nature, raises new questions nigh where these tall and slender early humans originated and how they adult sophisticated tool-making technology.

Early humans were using stone hand axes as far dorsum equally 1.viii million years ago. Credit: Pierre-Jean Texier, National Center of Scientific Research, France.

Homo erectus appeared virtually 2 1000000 years ago, and ranged across Asia and Africa earlier hitting a possible evolutionary dead-end, about 70,000 years ago. Some researchers call back Homo erectus evolved in East Africa, where many of the oldest fossils have been found, but the discovery in the 1990s of equally former Homo erectus fossils in the country of Georgia has led others to suggest an Asian origin.  The study in Nature does non resolve the fence only adds new complication. At 1.8 million years ago, Homo erectus in Dmanisi, Georgia was still using simple chopping tools while in Westward Turkana, Kenya, according to the study, the population had adult hand axes, picks and other innovative tools that anthropologists call "Acheulian."

"The Acheulian tools represent a great technological leap," said study co-writer Dennis Kent, a geologist with joint appointments at Rutgers Academy and Columbia Academy's Lamont-Doherty Earth Observatory. "Why didn't Man erectus accept these tools with them to Asia?"

In the summertime of 2007, a team of French and American researchers traveled to Republic of kenya'south Lake Turkana in Africa's Groovy Rift Valley, where earth'south plates are tearing apart and some of the primeval humans first appear. Anthropologist Richard Leakey'due south famous find--Turkana Male child, a Homo erectus teenager who lived about 1.v 1000000 years ago—was excavated on Lake Turkana's western shore and is still the near complete early human skeleton institute and so far.

Study co-writer, Craig Feibel, is among the team of researchers that returned in 2007 to West Turkana to put dates on hand axes excavated earlier. Credit: Lamont-Doherty Earth Observatory.

Six miles from Turkana Boy, the researchers headed for Kokiselei, an archeological site where both Acheulian and simpler "Oldowan" tools had been constitute before. Their goal: to institute the age of the tools by dating the surrounding sediments. By flooding in the expanse had left behind layers of silt and clay that hardened into mudstone, preserving the direction of Earth's magnetic field at the time in the stone's magnetite grains.  The researchers chiseled away chunks of the mudstone at Kokiselei to subsequently analyze the periodic polarity reversals and come up up with ages. At Lamont-Doherty'south Paleomagnetics Lab, they compared the magnetic intervals with other stratigraphic records to appointment the archeological site to i.76 million years.

"We suspected that Kokiselei was a rather quondam site, but I was taken aback when I realized that the geological data indicated it was the oldest Acheulian site in the world," said the written report'southward atomic number 82 author, Christopher Lepre, a geologist who likewise has articulation appointments at Rutgers and Lamont-Doherty. The oldest Acheulian tools previously identified announced in Konso, Ethiopia, almost 1.4 million years ago, and Republic of india, between 1.five million and 1 one thousand thousand years ago.

Tools made by early humans were found at Kokiselei, Kenya, in Lake Turkana's aboriginal shoreline sediments pictured above. Credit: Lamont-Doherty.

The Acheulian tools at Kokiselei were found just above a sediment layer associated with a polarity interval called the "Olduvai Subchron." It is named afterwards Tanzania's Olduvai Gorge, where pioneering work in the 1930s by Leakey's parents, Louis and Mary, uncovered a goldmine of early human fossils. In a study in Earth and Planetary Science Messages last year, Lepre and Kent establish that a well-preserved Human erectus skull found on east side of Lake Turkana, at Koobi Fora Ridge, also sat above the Olduvai Subchron interval, making the skull and Acheulian tools in West Turkana about the aforementioned age.

Anthropologists have yet to notice an Acheulian hand axe gripped in a Homo erectus fist but most credit Homo erectus with developing the technology. Acheulian tools were larger and heavier than the pebble-choppers used previously and besides had chiseled edges that would have helped Homo erectus butcher elephants and other scavenged game left behind past larger predators or even have immune the early humans to hunt such prey themselves. "You could whack away at a joint and dislodge the shoulder from the arm, leg or hip," said Eric Delson, a paleoanthropologist at CUNY's Lehman College who was not involved in the study. "The tools immune yous to cut open and dismember an animal to swallow it."

The skill involved in manufacturing such a tool suggests that Homo erectus was dexterous and able to think ahead. At Kokiselei, the presence of both tool-making methods—Oldowan and Acheulian-- could mean that Homo erectus and its more primitive cousin Human being habilis lived at the same time, with Man erectus carrying the Acheulian technology to the Mediterranean region most a million years ago, the study authors hypothesize.  Delson wonders if Human being erectus may have migrated to Dmanisi, Georgia, but "lost" the Acheulian technology on the way.

The East African landscape that Man erectus walked from about two million to 1.five million years agone was becoming progressively drier, with savanna grasslands spreading in response to changes in the monsoon rains. "Nosotros demand to understand as well the ancient environment considering this gives us an insight into how processes of evolution work—how shifts in early human biological science and behavior are potentially caused by changes in the climate, vegetation or animal life that is particular to a habitat," said Lepre. The team is currently excavating a more than two 1000000 year one-time site in Kenya to larn more about the early Oldowan period.

The study's other authors are: Helen Roche, Sonia Harmand, Jean-Philippe Brugal, Pierre-Jean Texier and Arnaud Lenoble at France's National Centre of Scientific Research; Rhonda Quinn, Seton Hall University; and Craig Feibel, Rutgers Academy.

Source: https://www.earth.columbia.edu/articles/view/2839

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