|
The Taung fossil -- the first australopithecine ever discovered --has two significant features that were analyzed by Falk and a groupof anthropological researchers. Their findings, which suggest brainevolution was a result of a complex set of interrelated dynamics inchildbirth among new bipeds, were published May 7 in the Proceedings of the National Academy of Sciences . "These findings are significant because they provide a highlyplausible explanation as to why the hominin brain might grow largerand more complex," Falk said. The first feature is a "persistent metopic suture," orunfused seam, in the frontal bone, which allows a baby's skull tobe pliable during childbirth as it squeezes through the birthcanal. In great apes -- gorillas, orangutans and chimpanzees -- themetopic suture closes shortly after birth. In humans, it does notfuse until around 2 years of age to accommodate rapid brain growth. The second feature is the fossil's endocast, or imprint of theoutside surface of the brain transferred to the inside of theskull. The endocast allows researchers to examine the brain's formand structure. After examining the Taung fossil, as well as huge numbers of skullsbelonging to apes and humans, as well as corresponding 3-D CT(three-dimensional computed tomographic) scans, and taking intoaccount the fossil record for the past 3 million years, Falk andher colleagues noted three important findings: The persistentmetopic suture is an adaptation for giving birth to babies withlarger brains; is related to the shift to a rapidly growing brainafter birth; and may be related to expansion in the frontal lobes. "The persistent metopic suture, an advanced trait, probablyoccurred in conjunction with refining the ability to walk on twolegs," Falk said. "The ability to walk upright caused anobstretric dilemma. Childbirth became more difficult because theshape of the birth canal became constricted while the size of thebrain increased. The persistent metopic suture contributes to anevolutionary solution to this dilemma." The later fusion of the metopic suture is most likely an adaptationof hominins who walked upright to be able to more easily give birthto babies with relatively large brains. The unfused seam is alsorelated to the shift to rapidly growing brains after birth, anadvanced human-like feature as compared to apes. "The later fusion was also associated with evolutionaryexpansion of the frontal lobes, which is evident from the endocastsof australopithecines such as Taung," Falk said. The Taung fossil, which is estimated to be around 2½ millionyears old, was discovered in 1924 in Taung, South Africa. It becamethe "type specimen," or main model, of the genusAustralopithecus africanus when it was announced in 1925. An australopithecine is any species of the extinct genera Australopithecus or Paranthropus that lived in Africa, walked on two legs and had relatively smallbrains. Falk conducted the research with Marcia S. Ponce de Leon, ChristophP.E. Zollikofer and Naoki Morimoto of the Anthropological Instituteand Museum at the University of Zurich in Switzerland. We are high quality suppliers, our products such as Drug Store Shelf Manufacturer , China Wine Display Rack for oversee buyer. To know more, please visits Stainless Steel Garment Rack.
Related Articles -
Drug Store Shelf Manufacturer, China Wine Display Rack,
|
