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人类祖先可能是内八字

2006-02-20 00:00

    Brain size and the ability to walk upright efficiently are two of the main attributes that separate humanity from the apes. Now researchers say learning to walk millions years ago was not without its trials.

    A re-examination of anklebones from early hominids indicates their gait was not as stable as previous research suggested.

    They were knock-kneed.

    A group of species known as robust australopithecines lived about 2 million years ago.

    Compared to us, they had larger teeth and stronger chewing muscles, a stouter skull with a smaller brain.

    Their feet were thought to be very much like ours, suggesting they had mastered bipedalism.

    "We noticed that in the specimens of robust australopithecines, there were characteristics of the anklebone that would have affected its bipedal locomotion," said Gary Schwartz, an Arizona State University anthropologist. "By looking at the location where the shin bone ides across the anklebone, we found that the shin bones would have been angled inward."

    Human ancestors go back as far as 6 million years, fossils show. The genus Homo arose at least 1.8 million years ago, scientists believe, when australopithecines likely evolved into human ancestors known as Homo habilis, which had larger brains but never grew larger than a 12-year-old child of today.

    Schwartz and Dan Gebo from Northern Illinois University compared the ancient anklebones of various species with those of today's gorillas, chimps and people.

    The results support the idea that bipedalism evolved only once.

    "The skeletal modifications associated with bipedalism represent a phenomenal reorganization of one's anatomy," Schwartz said. "It is unlikely that it could have evolved independently in multiple hominin lineages."

    But that doesn't mean the transition was smooth.

    "Think of the robust australopithecines as having developed a variation on the theme of bipedalism," Schwartz said. "Undoubtedly, it was not as efficient as the way we walk today, but it might have conferred some other evolutionary advantages."

    The researchers have no idea how being knock-kneed might have been an advantage, but they plan to explore the question next.



    美国研究人员通过对早期原始人类的踝关节进行重新研究后发现,早期人类的步态并非如同此前人们认为的那么稳健。研究人员指出,数百万年前,早期人类学习直立行走的过程并不简单,我们的一些早期祖先还是八字脚。

    据“生活科学”2月16日报道,粗壮型南猿(robust Australopithecines)是生活在大约200万年之前的一个物种。和我们相比,他们拥有更大的牙齿和更为强壮的咀嚼肌,同时他们的头骨也更强壮一些但脑部较小。此前,研究人员曾认为,粗壮型南猿的脚和我们的很相似,并由此认为他们可以熟练地用两只脚行走。

    此项研究的参与者、美国亚利桑那州立大学的人类学家加里·施瓦兹对此表示:“我们注意到,在粗壮型南猿的化石样本中,其踝骨的一些特性可能影响到了他们作为两足动物的运动。通过查看他们胫骨和踝骨相接的位置,我们发现他们的胫骨都呈一定角度向内侧弯曲。”

    报道说,施瓦兹和来自美国北伊利诺伊大学的丹·盖博用各种原始人类的踝骨与现代大猩猩、黑猩猩以及人类的踝骨进行了比较。具体的研究结果将被发表在2006年4月份的《美国身体人类学杂志》上。研究人员还将对这一问题进行更为深入的研究。

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