Oldest 'Footprints' on Earth Found
The oldest-known tracks of a creature apparently using legs have been discovered in rock dated to 570 million years ago in what was once a shallow sea in Nevada.
Scientists think land beasts evolved from ancient creatures that left the sea and evolved lungs and legs. If the new finding is real - the discoverer anticipates skepticism - it pushes the advent of walking back 30 million years earlier than any previous solid finding.
The aquatic creature left its "footprints" as two parallel rows of small dots, each about 2 millimeters in diameter. Scientists said today that the animal must have stepped lightly onto the soft marine sediment, because its legs only pressed shallow pinpoints into that long-ago sea bed.
The tracks were made during what is called the Ediacaran period, which preceded the Cambrian period, the time when most major groups of animals first evolved. Scientists had once thought only microbes and simple multicellular animals existed prior to the Cambrian, but that notion is changing, said Ohio State University Professor Loren Babcock.
"We keep talking about the possibility of more complex animals in the Ediacaran - soft corals, some arthropods, and flatworms - but the evidence has not been totally convincing," Babcock said. "But if you find evidence, like we did, of an animal with legs - an animal walking around - then that makes the possibility much more likely."
Soo-Yeun Ahn, a doctoral student at Ohio State, presented the discovery today at a meeting of the Geological Society of America.
Babcock was surveying rocks in the mountains near Goldfield, Nevada, with Hollingsworth in 2000 when he found the tracks.
"This was truly an accidental discovery," he said. "We came on an outcrop that looked like it crossed the Precambrian-Cambrian boundary, so we stopped to take a look at it. We just sat down and started flipping rocks over. We were there less than an hour when I saw it."
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Egalitarian Revolution In The Pleistocene?
Although anthropologists and evolutionary biologists are still debating this question, a new study supports the view that the first egalitarian societies may have appeared tens of thousands of years before the French Revolution, Marx, and Lenin.
These societies emerged rapidly through intense power struggle and their origin had dramatic implications for humanity. In many mammals living in groups, including hyenas, meerkats, and dolphins, group members form coalitions and alliances that allow them to increase their dominance status and their access to mates and other resources. Alliances are especially common in great apes, some of whom have very intense social life, where they are constantly engaged in a political maneuvering as vividly described in Frans de Waal's "Chimpanzee politics".
In spite of this, the great apes' societies are very hierarchical with each animal occupying a particular place in the existing dominance hierarchy. A major function of coalitions in apes is to maintain or change the dominance ranking. When an alpha male is well established, he usually can intimidate any hostile coalition or the entire community.
In sharp contrast, most known hunter-gatherer societies are egalitarian. Their weak leaders merely assist a consensus-seeking process when the group needs to make decisions, but otherwise all main political actors behave as equal. Some anthropologists argue that in egalitarian societies the pyramid of power is turned upside down with potential subordinates being able to express dominance over potential alpha-individuals by creating large, group-wide political alliance.