Word: bone
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...team eventually found 11 specimens--from at least five different individuals--in a cluster of sites, including Haile-Selassie's partial lower jaw with associated teeth, several hand and foot bones, and pieces of three arm bones and a collarbone. Luckily, the fossils were trapped in sediments that were sandwiched between layers of volcanic ash, whose age can be accurately gauged by a technique known as argon-argon dating. (This layering is still visible in places that have not been so heavily eroded, enabling the scientists to trace the area's geologic history.) The verdict, confirmed by a second dating...
...unlike a chimp or any of the other modern apes that amble along on four limbs, kadabba almost certainly walked upright much of the time. The inch-long toe bone makes that clear. Two-legged primates (modern humans included) propel themselves forward by leaving the front part of their foot on the ground and lifting the heel. This movement, referred to as toeing off, causes the bones in the middle of the foot to take on a distinctive shape--a shape that is readily apparent in the ancient toe bone. "If you compare a chimp's foot bones with...
Changes also had to take place in the femur, or thighbone. For example, the femoral neck--the bent portion at the top of the bone--is broader in humans than it is in apes, which improves balance. The human knee is specialized for walking upright too: to compensate for the thighbone's being at an angle, there's a lump, or groove, at the end of the femur that prevents the patella from sliding off the joint. "A chimp doesn't have this groove because there is no angulation between the hip and the knee," Lovejoy says. "This change says...
...became aligned with the others, and the toe's muscles and ligaments, which had been used for grasping and climbing, were repositioned under the foot. "The shape of the big toe is indicative of this. You can see it in Lucy's species," Lovejoy says, but not in the bone Haile-Selassie found, because it's from a different toe. "What we can see [in the new discovery's foot] is that the base of the bone adjacent to the knuckle has a distinct angle, showing that the creature walked step after step after step with its heel...
Republican Senator Sam Brownback, below left, believes a "wonderful" compromise for Bush would be to increase greatly funding for research on adult stem cells, which are harvested from bone marrow and brain tissue and have begun to show some of the same potential as those derived from embryos. But scientists aren't so sure. It's not yet clear whether adult stem cells will prove as versatile as embryonic ones, particularly in developing cures for Parkinson's disease and diabetes. Researchers also note that it is more difficult to produce large quantities of adult stem cells, and fear they...