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Earliest evidence of humans thriving on the savannah

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Doxtator
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« on: October 23, 2009, 01:06:09 am »



Home |Life | News
Earliest evidence of humans thriving on the savannah

    * 18:07 21 October 2009 by Shanta Barley
    * For similar stories, visit the Human Evolution Topic Guide

Humans were living and thriving on open grassland in Africa as early as 2 million years ago, making stone tools and using them to butcher zebra and other animals. That's according to powerful evidence from artefacts found at Kanjera South, an archaeological site in south-west Kenya.

"There is no clear evidence of any hominin being associated with or foraging in open grassland prior to this 2-million-year-old site," says Thomas Plummer of Queens College at the City University of New York.

All of the other earlier hominins that have been found in the geological record – such as Ardipithecus ramidus and Australopithecus afarensis – known as Ardi and Lucy, respectively - lived either in dense forest or in a mosaic of woodland, shrub and grasses, says Plummer.

The Kanjera South site now offers a glimpse into the lives of our ancestors as they were starting to adapt to life on the plains. "The site occurs in a grassland setting, dominated by grass-eating animals, and is thus the first clear evidence that grasslands were indeed part of the diversity of environments inhabited by early human tool-makers," says team member Richard Potts of the Smithsonian Institution's National Museum of Natural History in Washington DC.
Carbon captured

Plummer's team first started excavating Kanjera South in the 1990s, in search of primitive toolkits consisting of hammer stones, stone cores that were struck to create sharp edges, and stone slivers. In the process, they uncovered the fossils of 2190 different animals and 2471 tools, all deposited within a window of just decades to a few centuries.

To investigate whether they were standing on the site of ancient grassland, Plummer's team analysed the ratio of carbon-13 to carbon-12 in the soil and in the tooth enamel of the fossilised animals. Grass has a higher ratio than trees and shrubs. Both the soil and the tooth enamel of fossilised animals had similarly high ratios.

"These tests showed that the Kanjera site was over 75 per cent grassland 2 million years ago, and that the wider area was teeming with zebras, antelope and other grazers," says Plummer. The telltale carbon isotope ratio was seen in all the animals, suggesting they were all grazing on grass. "This is not what you would see if you were drawing this faunal sample from a heavily wooded region, with a small patch of grassland in it."

The team also found that the site was littered with the fossils of young, butchered zebra carcasses. The youth of the prey suggested that the hominins were hunting these animals rather than scavenging for them.
Open seasons

Plummer's team also found that the ancient humans who lived in Kanjera 2 million years ago carried stone raw materials over surprisingly long distances. "These early humans carried high-quality, hard stone from over 13 kilometres away to the site," says Plummer.

"This is the first really convincing and comprehensive demonstration of an early hominin living on grassland," says anthropologist Bernard Wood of George Washington University in Washington DC.

Rene Bobe at the University of Georgia in Athens, agrees: "This finding actually shows something that has been suspected; that hominids were occupying grasslands by 2 million years ago and that this kind of open environment likely played a key role in the evolution of human adaptations."

Journal reference: PLoS ONE, DOI: 10.1371/journal.pone.0007199

If you would like to reuse any content from New Scientist, either in print or online, please contact the syndication department first for permission. New Scientist does not own rights to photos, but there are a variety of licensing options available for use of articles and graphics we own the copyright to.
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Hominids Or Hominins Or Humans?

Wed Oct 21 19:32:20 BST 2009 by Liza

Since the article mentions no human fossils, I suppose none have been found in association with the tools. A pity, because that would have been much more informative. Apparently we cannot known which human ancestor or cousin lived there.
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Hominids Or Hominins Or Humans?

Wed Oct 21 20:39:49 BST 2009 by Hasham

The specific wording "humans" makes me think it can't be anything but homo sapiens.
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Hominids Or Hominins Or Humans?

Wed Oct 21 22:32:25 BST 2009 by Rivd
http://freetubetv.net

actually you mean homo sapien sapien.
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Hominids Or Hominins Or Humans?

Thu Oct 22 02:05:25 BST 2009 by Homo Sapiens

Homo Sapiens didn't exist two million years ago. This is a human ancestor of some variety. We do need to know which one it was to determine the relevance of the research.
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Homo Erectus?

Wed Oct 21 20:59:22 BST 2009 by Thomas

If yes, it would fit to other findings, saying ca. that homo erectus was the first "real human": They had a much smaller brain and no modern language skills, but lived in something like huts around central paved places, used fire, became independent from a specific ecological nice, competed carnivores out of their ways, made specialized stone tools. An expert in reconstructing those stone tools said in a recent docu, a modern human would need ca. 2-3 weeks of intense and guided training to reproduce them.

The homini erecti probably were the first hominids who became "personas", because the heights of women suddenly increased after some climate change modified their food collecting methods. Earlier women were ca. half as high as men, male homo erectus' were ca. 1.80 m, women-h-e's ca. 1.40 m high. This change forced homini-erecti-women to avert a "monopolization" by dominant males, because the later would not have been able to nourish them any more. But the males' perception systems were still adapted to small women, so that they had trouble to perceive the startling elongated women as such. Women used that to invent some sort of attractive cosmetics and aliennating camouflage for guiding how they were perceived. In an other New Scientist article, an archeologist speculates that women dressed each full moon with animal parts and ashes as gastly "zombies" to drive males out of the settlements for hunting - when the males returned, suddenly the "zombies" had become attractive women again. This way, homo erectus women invented culture. IMO that could have been the root of advanced nonverbal social skills and social role playing. Perhaps our intuition about other people comes from those times and stayed on the level? Speculating more about that, one can draw interesting conclusions, e.g. about social skills and advanced mental functions.
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Species?

Wed Oct 21 21:49:42 BST 2009 by Robert Davis

Re., Hasham

Rest assured that these were not Homo sapiens two million years ago. Homo sapiens cannot be reasonably assumed to have existed more than about 200,000 years ago.

The two million year date would suggest they were some of the earliest of Homo erectus (or some might say Homo ergaster). The authors must have used the term "human" because there were no hominid fossils found that might suggest the identity of the users of the tools. And since we don't know of any tool use among the Australopithicenes, it's also reasonable to assume that they were members of the genus Homo--reasonable enough to refer to them as human.

It would have been interesting if the authors had mentioned, more specifically, what type of tools were found. My assumption is that they were of the Acheulean type--which fits with their modest description. This find does represent a valuable piece of the puzzle in our understanding of early man; but, given what we already know, it would punch serious holes in our assumptions about the physical and behavioral evolution of hominids, if the tools were not of the Acheulean variety or if the users in question were not Homo erectus.
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Species?

Wed Oct 21 22:12:53 BST 2009 by Liza

"it would punch serious holes in our assumptions about the physical and behavioral evolution of hominids, if the tools were not of the Acheulean variety or if the users in question were not Homo erectus."

Quite right, just as the rest of your explanation. And that is why it was very sloppy of the authors not to mention the presence or absence of hominin fossils, or not to offer a suggestion on who may have used the tools. The term "human" specifically means Homo sapiens, so Hasham was right. NS should know better than using the terms human, hominid and hominin indiscriminately in an article on human evolution.
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Species?

Wed Oct 21 23:26:21 BST 2009 by I Doubt That

Robert Davis - "It would have been interesting if the authors had mentioned, more specifically, what type of tools were found. My assumption is that they were of the Acheulean type--which fits with their modest description."

I read about this earlier today at Science Daily http://www.sciencedaily.com/releases/2009/10/091020203420.htm and it says "Oldowan tools". Acheulean tools do not appear until later, at 1.5mya.

Btw Science Daily has a very good collection of articles about human evolution, well worth checking out.
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Qoais
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« Reply #1 on: October 23, 2009, 04:35:29 pm »

Scientists should just admit they've got the time lines wrong and correct the problem.  We're older than we think, and have been smarter longer as well.
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An open-minded view of the past allows for an unprejudiced glimpse into the future.

Logic rules.

"Intellectual brilliance is no guarantee against being dead wrong."
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