Word: ardipithecus
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...more than 100 additional bone fragments were found during an intensive search-and-reconstruction effort that would go on for the next 15 years and culminate in a key piece of evolutionary evidence revealed this week: the 4.4 million-year-old skeleton of a likely human ancestor known as Ardipithecus ramidus (abbreviated Ar. ramidus). (See the top 10 scientific discoveries...
...good bones. The completeness of Ardi's remains, as well as the more than 150,000 plant and animal fossils collected from surrounding sediments of the same time period, has generated an unprecedented amount of intelligence about one of our earliest potential forebears. The skeleton allows scientists to compare Ardipithecus directly with Lucy's genus, Australopithecus, its probable descendant. Perhaps most important, Ardi provides clues to what the last common ancestor shared by humans and chimps might have looked like before their lineages diverged about 7 million years ago. (See pictures of ancient skeletons...
...knows what that reason was, but a theory about Ardi's social behavior may hold a clue. Lovejoy thinks Ar. ramidus had a social system found in no other primates except humans. Among gorillas and chimps, males viciously fight other males for the attention of females. But among Ardipithecus, says Lovejoy, males may have abandoned such competition, opting instead to pair-bond with females and stay together in order to rear their offspring (though not necessarily monogamously or for life). The evidence of this harmonious existence comes from, of all things, Ardipithecus' teeth: its canine teeth are relatively stubby compared...
...split from a common ancestor no more than 6.3 million years ago and probably less than 5.4 million years ago. If they're correct, several hominid species now considered to be among our earliest ancestors--Sahelanthropus tchadensis (7 million years old), Orrorin tugenensis (about 6 million years old) and Ardipithecus kadabba (5.2 to 5.7 million years old)--may have to be re-evaluated...
...University of California, Berkeley, disputes the assertion that Toumai derails the standard evolutionary family tree, let alone plants a bush in its place. The discovery is a tremendous accomplishment, he says. "This fossil is the closest we've got to the common ancestor. But dentally, it's just like Ardipithecus, except for a few minor characteristics." The mix of primitive and more advanced traits leaves him similarly unimpressed, since such mixing has been seen in various species discovered over the past 80 years. In spite of what his colleagues say, White believes that Toumai may well be the direct ancestor...