Dan orang Islam yang dungu-dungu kayak anjing itu masih percaya allah takhayul
itu menciptakan Adam danSiti Hawa..
Harga diri, itulah yang tidak dimiliki orang Islam itu.
Web address:
http://www.sciencedaily.com/releases/2012/12/
121231161043.htm
Did Lucy Walk On the Ground or Stay in the Trees?
enlarge
Men in Twa society from Uganda regularly climb trees to gather honey. (Credit:
Nathaniel Dominy)
Dec. 31, 2012 Much has been made of our ancestors "coming down out of the
trees," and many researchers view terrestrial bipedalism as the hallmark of
"humanness." After all, most of our living primate relatives -- the great apes,
specifically -- still spend their time in the trees. Humans are the only member
of the family devoted to the ground, living terrestrial rather than arboreal
lives, but that wasn't always the case.
The fossil record shows that our predecessors were arboreal habitués, that is,
until Lucy arrived on the scene. About 3.5 million years ago in Africa, this
new creature, Australopithecus afarensis, appeared; Lucy was the first specimen
discovered. Anthropologists agree that A. afarensis was bipedal, but had Lucy
and her legions totally forsaken the trees? The question is at the root of a
controversy that still rages.
"Australopithecus afarensis possessed a rigid ankle and an arched, nongrasping
foot," write Nathaniel Dominy and his co-authors in Proceedings of the National
Academy of Sciences (PNAS). "These traits are widely interpreted as being
functionally incompatible with climbing and thus definitive markers of
terrestriality," says Dominy, an associate professor of anthropology at
Dartmouth.
But not so fast; this interpretation may be a rush to judgment in light of new
evidence brought to light by Dominy and his colleagues. They did what
anthropologists do. They went out and looked at modern humans who, like Lucy,
have feet adapted to terrestrial bipedalism, and found these people can still
function as effective treeclimbers.
Co-authors Vivek Venkataraman and Thomas Kraft collaborated with Dominy on
field studies in the Philippines and Africa that inform their PNAS paper.
Venkataraman and Kraft are Dartmouth graduate students in the Ecology and
Evolutionary Biology PhD program in the Department of Biological Sciences, and
are supported by National Science Foundation graduate research fellowships.
The studies in Uganda compared Twa hunter-gatherers to their agriculturalist
neighbors, the Bakiga. In the Philippines, the researchers studied Agta
hunter-gatherers and Manobo agriculturalists. Both the Twa and the Agta
habitually climb trees in pursuit of honey, a highly nutritious component of
their diets. They climb in a fashion that has been described as "walking" up
small-diameter trees. The climbers apply the soles of their feet directly to
the trunk and "walk" upward, with their arms and legs advancing alternately.
Among the climbers, Dominy and his team documented extreme dorsiflexion --
bending the foot upward toward the shin to an extraordinary degree -- beyond
the range of modern "industrialized" humans. Assuming their leg bones and ankle
joints were normal, "we hypothesized that a soft-tissue mechanism might enable
such extreme dorsiflexion," the authors write.
They tested their hypothesis using ultrasound imaging to measure and compare
the lengths of gastrocnemius muscle fibers -- the large calf muscles -- in all
four groups -- the Agta, Manobo, Twa and Bakiga. The climbing Agta and Twa were
found to have significantly longer muscle fibers.
"These results suggest that habitual climbing by Twa and Agta men changes the
muscle architecture associated with ankle dorsiflexion," write the scientists,
demonstrating that a terrestrially adapted foot and ankle do not exclude
climbing from the behavioral repertoire of human hunter- gatherers, or Lucy.
In their conclusions, the Dartmouth team highlights the value of modern humans
as models for studying the anatomical correlates of behavior, both in the
present and in the dim past of our fossil ancestors.
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Story Source:
The above story is reprinted from materials provided by Dartmouth College.
The original article was written by Joseph Blumberg.
Note: Materials may be edited for content and length. For further
information, please contact the source cited above.
Journal Reference:
Vivek V. Venkataraman, Thomas S. Kraft, and Nathaniel J. Dominy. Tree
climbing and human evolution. Proceedings of the National Academy of Sciences,
2012; DOI: 10.1073/pnas.1208717110
Need to cite this story in your essay, paper, or report? Use one of the
following formats:
APA
MLA
Dartmouth College (2012, December 31). Did Lucy walk on the ground or stay in
the trees?. ScienceDaily. Retrieved January 1, 2013, from
http://www.sciencedaily.com /releases/2012/12/121231161043.htm
Note: If no author is given, the source is cited instead.
Disclaimer: Views expressed in this article do not necessarily reflect those of
ScienceDaily or its staff.
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