Chimp-sized hominid walked upright on two legs six million years ago, researchers say

<body leftmargin="0" bgcolor="#000060" text="#FFFFFF" link="#FFFF00" vlink="#FF9900"> <p class="MsoNormal"><b><font face="Arial" size="4">Chimp-sized hominid walked upright on two legs six million years ago, researchers say</font></b></p> <p class="MsoNormal"><font face="Arial" size="1">Posted Sept. 2, 2004<br> Penn State University and<br> World Science Staff</font><font face="Arial" color="#ffffff" size="2"><b><br> <br> Recent fossil evidence suggests that a hominid, the size of a chimp, walked upright on two legs in Kenya's Tugen Hills, over 6 million years ago --- about 3 million years earlier than "Lucy," the most famous early biped in our lineage.</b></font></p> <table style="FLOAT: right" cellSpacing="0" cellPadding="0" width="200" border="0"> <tbody> <tr> <td><img style="BORDER-RIGHT: #ffffff 2px ridge; BORDER-TOP: #ffffff 2px ridge; BORDER-LEFT: #ffffff 2px ridge; BORDER-BOTTOM: #ffffff 2px ridge" height="147" src="http://www.eurekalert.org/images/release_graphics/PSU0902_2sm.jpg" width="200" border="0"></td> </tr> <tr> <td><font face="Arial" size="1">Reconstruction of the fossil bone from CT slices. (Courtesy Penn State)</font></td> </tr> </tbody> </table> <p class="MsoNormal"><font face="Arial" color="#ffffff" size="2"><b>Dr. Robert Eckhardt, professor of developmental genetics and evolutionary morphology, Laboratory of Comparative Morphology and Mechanics (LCMM), Department of Kinesiology at Penn State, led the U.S. research team responsible for analysis of the CT scans of the internal structure of the fossil bone. Eckhardt says, "We have solid evidence of the earliest upright posture and bipedalism securely dated to six million years." <O:P> </O:P> <O:P> </O:P> </b></font></p> <p class="MsoNormal"><font face="Arial" color="#ffffff" size="2"><b>The evidence is detailed in the current (Sept. 3) issue of the research journal Science. <O:P> </O:P> </b></font></p> <p class="MsoNormal"><font face="Arial" color="#ffffff" size="2"><b>The fossil the team studied is part of a left thighbone unearthed nearly four years ago by Senut and Pickford at their dig in the Kenyan Lukeino Formation. The fragment includes the intact head of the left thighbone -- the ball that is inserted into the hip socket joint -- plus the bony neck that connects the ball to the thighbone shaft as well as part of the thighbone shaft. <O:P> </O:P> <O:P> </O:P> </b></font></p> <p class="MsoNormal"><font face="Arial" color="#ffffff" size="2"><b>Measurements show that the fossil bone is about the same size as a chimpanzee's. However, CT scans of the interior of the bone reveal that the neck connecting the ball to the shaft is thinner on top than it is on the bottom, a sign the researchers say that the individual from which it came walked on two legs. <O:P> </O:P> </b></font></p> <p class="MsoNormal"><font face="Arial" color="#ffffff" size="2"><b>Eckhardt says, "In present day chimps and gorillas, the thicknesses in the upper and lower parts of that bone are approximately equal. In modern humans, the bone on top is thinner than on the bottom by a ratio of one to four or more. The ratio in this fossil is one to three." <O:P> </O:P> </b></font></p> <p class="MsoNormal"><font face="Arial" color="#ffffff" size="2"><b>The ratio in the fossil is evidence for transition to an upright posture and habitual bipedal gait the researchers argue. In addition, Eckhardt notes, because walking upright is the essential mark of a hominid, the ratio is functional evidence that the bones fossilized at Lukeino were from hominids.</b></font></p> </body>