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News: THE SEARCH FOR ATLANTIS IN CUBA
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Top Ten Dinosaur and Fossil Finds: Most Viewed of 2009

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Author Topic: Top Ten Dinosaur and Fossil Finds: Most Viewed of 2009  (Read 4253 times)
Tyrannosaurus Rex
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« Reply #45 on: December 28, 2009, 06:42:40 am »

Sex for Food

Some researchers, however, are unconvinced that Ardipithecus was quite so versatile.

"This is a fascinating skeleton, but based on what they present, the evidence for bipedality is limited at best," said William Jungers, an anatomist at Stony Brook University in New York State.

"Divergent big toes are associated with grasping, and this has one of the most divergent big toes you can imagine," Jungers said. "Why would an animal fully adapted to support its weight on its forelimbs in the trees elect to walk bipedally on the ground?"

One provocative answer to that question—originally proposed by Lovejoy in the early 1980s and refined now in light of the Ardipithecus discoveries—attributes the origin of bipedality to another trademark of humankind: monogamous sex.

Virtually all apes and monkeys, especially males, have long upper canine teeth—formidable weapons in fights for mating opportunities.

But Ardipithecus appears to have already embarked on a uniquely human evolutionary path, with canines reduced in size and dramatically "feminized" to a stubby, diamond shape, according to the researchers. Males and female specimens are also close to each other in body size.

Lovejoy sees these changes as part of an epochal shift in social behavior: Instead of fighting for access to females, a male Ardipithecus would supply a "targeted female" and her offspring with gathered foods and gain her sexual loyalty in return.

To keep up his end of the deal, a male needed to have his hands free to carry home the food. Bipedalism may have been a poor way for Ardipithecus to get around, but through its contribution to the "sex for food" contract, it would have been an excellent way to bear more offspring. And in evolution, of course, more offspring is the name of the game (more: "Did Early Humans Start Walking for Sex?").

Two hundred thousand years after Ardipithecus, another species called Australopithecus anamensis appeared in the region. By most accounts, that species soon evolved into Australopithecus afarensis, with a slightly larger brain and a full commitment to a bipedal way of life. Then came early Homo, with its even bigger brain and budding tool use.

Did primitive Ardipithecus undergo some accelerated change in the 200,000 years between it and Australopithecus—and emerge as the ancestor of all later hominids? Or was Ardipithecus a relict species, carrying its quaint mosaic of primitive and advanced traits with it into extinction?

Study co-leader White sees nothing about the skeleton "that would exclude it from ancestral status." But he said more fossils would be needed to fully resolve the issue.

Stony Brook's Jungers added, "These finds are incredibly important, and given the state of preservation of the bones, what they did was nothing short of heroic.

But this is just the beginning of the story."

Look for comprehensive coverage of Ardipithecus ramidus in a future issue of National Geographic magazine.

More From National Geographic Magazine
• Fossil Ape: Human Ancestor?
• Childhood Origins
• Human Evolutionary Highway

More Human Evolution News Coverage
• Humans, Chimps Not as Closely Related as Thought? (September 24, 2002)
• Chimps Belong on Human Branch of Family Tree, Study Says (May 23, 2003)
• Oldest Human Fossils Identified (February 16, 2005)
• Chimps, Humans 96 Percent the Same, Gene Study Finds (August 31, 2005)
• Human Genome Shows Proof of Recent Evolution, Survey Finds (March 8, 2006)
• Human, Chimp Ancestors May Have Mated, DNA Suggests (May 17, 2006)
• Human Evolution Speeding Up, Study Says (December 11, 2007)
• "MISSING LINK" FOUND: New Fossil Links Humans, Lemurs? (May 19, 2009)
• Orangutans May Be Closest Human Relatives, Not Chimps (June 23, 2009)


http://news.nationalgeographic.com/news/2009/10/091001-oldest-human-skeleton-ardi-missing-link-chimps-ardipithecus-ramidus.html
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