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I am reading the Science special issue on Ardipithecus ramidus, which looks like it was our ancestor 4.4 million years ago. Very cool stuff, including bits that nobody was expecting. On the large scale: it looks as though significant parts of human anatomy are "primitive" relative to the last common ancestor (LCA) with chimpanzees and bonobos, and Pan is more derived. Looking at the fossils, there was never any good reason to think that we had knuckle-walking ancestors, and Ardi makes it pretty definite that we didn't: that hominid was either walking along the tops of tree limbs (not brachiating) or walking, but not running, on the ground. But it was easy for people to think that chimps are more "primitive," and therefore that the LCA was more chimp-like. The only useful meaning of "primitive" here is "less different from the ancestral form," and the complement is "derived." Opposable thumbs appear to be primitive, and Ardipithecus probably used theirs for grasping the branches they were walking along. Apparently nobody was expecting an ancestor whose wrists would bend back as far as Ardi's seem to have, but it would have been very useful for the walking-on-branches.
This is a set of reports on 15 years of fossil-collecting, reconstruction, and analysis. The best single specimen, which the scientists have nicknamed "Ardi," is more complete than Lucy, and also female. The fossil site is in an area called Awash, and this specific layer is the Middle Awash. The broader area is Afar, and the headline-writers gave in to temptation and have now, in two different issues, used the headline "The View from Afar." Fair enough: 4.4 million years is a significant distance (apparently two genera back). Some of the articles are only online; others, and summaries of all of them, are in the printed issue. One of the summaries includes the broadest acknowledgement I have ever seen in a scientific paper: to the people of Ethiopia, for preserving and curating the fossils and sites. There are comparisons to Lucy and other Australopithecines. (I have discovered that the convention, when two genera begin with the same letter, is to start writing Ar. ramidus and Au. afaransis, instead of A. afarensis.) Lots of teeth, of course; quite a few bones; and the researchers have picked the site clean of every bit of fossil anything, so they have a fairly good idea of the woodland habitat as well.
Obviously, some of the conclusions will be debated for years. For example: Ardipithecus, female and male, had small canines, rather like ours, not the larger canines that chimp and bonobo males use for intra-species aggression. The paper referred to those teeth as "feminized." Another paper points out that there wasn't much size difference between male and female: a meter or so tall, about 50 kg, for adults. Based on that and the teeth, the research team has concluded that the social structure was somewhat more like humans, and less like chimps, than previously assumed. (In living primates, strong size dimorphism tends to correlate with stronger male dominance and polygyny.) The teeth are a fact; the conclusions about social structure are speculation, because behavior doesn't fossilize. (The teeth are a solider fact than the similar body sizes, because we have a lot of teeth: they fossilize much better than bones.) The tooth shape and enamel suggest a mixed diet, with less fruit than the modern chimp diet, but mostly plants.
There are comparisons here not only to Australopithecus, but back to Sahelanthropus (7 mya) and Orrorin, but those taxa aren't as well known. One or both of those species may wind up in Ardipithecus, when this is sorted out a bit more, and/or when we get more bones of those older species. For context, the writers go back to Darwin, and his observation that he couldn't really say much about our ancestors, since we had no fossils further back than the Neanderthals when he was writing.
This is a set of reports on 15 years of fossil-collecting, reconstruction, and analysis. The best single specimen, which the scientists have nicknamed "Ardi," is more complete than Lucy, and also female. The fossil site is in an area called Awash, and this specific layer is the Middle Awash. The broader area is Afar, and the headline-writers gave in to temptation and have now, in two different issues, used the headline "The View from Afar." Fair enough: 4.4 million years is a significant distance (apparently two genera back). Some of the articles are only online; others, and summaries of all of them, are in the printed issue. One of the summaries includes the broadest acknowledgement I have ever seen in a scientific paper: to the people of Ethiopia, for preserving and curating the fossils and sites. There are comparisons to Lucy and other Australopithecines. (I have discovered that the convention, when two genera begin with the same letter, is to start writing Ar. ramidus and Au. afaransis, instead of A. afarensis.) Lots of teeth, of course; quite a few bones; and the researchers have picked the site clean of every bit of fossil anything, so they have a fairly good idea of the woodland habitat as well.
Obviously, some of the conclusions will be debated for years. For example: Ardipithecus, female and male, had small canines, rather like ours, not the larger canines that chimp and bonobo males use for intra-species aggression. The paper referred to those teeth as "feminized." Another paper points out that there wasn't much size difference between male and female: a meter or so tall, about 50 kg, for adults. Based on that and the teeth, the research team has concluded that the social structure was somewhat more like humans, and less like chimps, than previously assumed. (In living primates, strong size dimorphism tends to correlate with stronger male dominance and polygyny.) The teeth are a fact; the conclusions about social structure are speculation, because behavior doesn't fossilize. (The teeth are a solider fact than the similar body sizes, because we have a lot of teeth: they fossilize much better than bones.) The tooth shape and enamel suggest a mixed diet, with less fruit than the modern chimp diet, but mostly plants.
There are comparisons here not only to Australopithecus, but back to Sahelanthropus (7 mya) and Orrorin, but those taxa aren't as well known. One or both of those species may wind up in Ardipithecus, when this is sorted out a bit more, and/or when we get more bones of those older species. For context, the writers go back to Darwin, and his observation that he couldn't really say much about our ancestors, since we had no fossils further back than the Neanderthals when he was writing.
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