Ida: Humankind's Earliest Ancestor! (Not Really)
By Michael D. Lemonick Thursday, May. 21, 2009
From the beginning, Ida's unveiling has been a master class in ballyhoo. A week ago, the first breathless press releases began to arrive, portending the presentation of the now famous 47-million-year-old primate fossil from Germany: "MEDIA ALERT," the notice shouted in all caps. "WORLD-RENOWNED SCIENTISTS REVEAL A REVOLUTIONARY SCIENTIFIC FIND THAT WILL CHANGE EVERYTHING." This isn't exactly the stamp of approval most scientists look for, though, and in this case the puffery is especially unfortunate because the actual scientific finding, described in a paper published on May 19 in the online journal PLoS One, really is important.
First, the young mammal, which would have looked like a cross between a lemur and a small monkey, is astonishingly complete. "Most of what we understand about primate evolution is pieced together from bits of teeth and jaws," says Michael Novacek, curator of paleontology at the American Museum of Natural History. Ida, by contrast, has pretty much every bone, from the skull to the tip of the tail, and they're all in place. Not only that: you can see impressions of its fur in the surrounding material, and there are even the remains of what was presumably Ida's final meal (leaves and fruit) still visible where the digestive tract used to be.
The fossil is so perfectly preserved because Ida probably died quickly and nonviolently; her resting place was an abandoned quarry called the Messel Pit, near Frankfurt. At the time she lived, the pit was a lake out of which poisonous volcanic gases probably belched from time to time. Likely felled by such an outburst, she tumbled into deep, oxygen-poor water where she would have been buried by sediments before she could decompose. Indeed, the Messel Pit is such a rich source of well-preserved fossils that it's been designated a UNESCO World Heritage Site. (Read about China's fossil trade.)
The second reason the discovery is so important is its age. Ida — her scientific name is Darwinius masillae — dates to about 47 million years ago, when temperatures were warmer than they are today and when mammals underwent a burst of evolutionary diversification. In particular, that's when primates began splitting off into two branches. One became anthropoids, whose descendants are monkeys, apes and humans. The other turned into prosimians — lemurs and their kin. (See pictures of a bonobo eden.)
Ida is intriguing because she has some characteristics of both branches, which suggests that she could be a transitional animal that gave rise to the anthropoids and, ultimately, to us. "How transitional it is," says Novacek, "is a matter of debate and further study. I expected that from the beginning. The ratio of vertebrate paleontologists to actual specimens is high, which makes for a lot of theorizing." A specimen like this will reduce the theorizing, but in the end it may not settle anything at all.
THE ARTICLE CONTINUES ON THIS LINK:
http://www.time.com/time/health/article/0,8599,1900057,00.html
No comments:
Post a Comment