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Re: escaping preds in H2O
johman@welchlink.welch.jhu.edu
26 Sep 1995 16:45:14 GMT
Alex Duncan <aduncan@mail.utexas.edu> wrote:
>In article <hubey.811404140@pegasus.montclair.edu> H. M. Hubey,
>hubey@pegasus.montclair.edu writes:
>
>>I also think that the scenario produces a brutally efficient
>>selection mechanism. First of all if there was an attack from
>>some nearby cats, they'd get the ones with short legs who'd
>>be forced to stay nearer the shore. The bigger ones would
>>wade in deeper to escape while the cats got their lunch from
>>the little ones. Under this scenario, there'd be a premium
>>on long legs, in addition to being taller, since they'd
>>wade into deeper water and further from the shore while their
>>little cousins became breakfast, lunch and dinner.
>
>Why not just use the equipment you were given as a result of your
>generalized primate ancestry, and climb a tree?
>
>There's a problem w/ the idea that there's a premium on long legs: for
>at least 2 Myr hominids had hindlimbs that were about the same length
>relative to body size as is the case in modern chimps.
>
>Alex Duncan
>Dept. of Anthropology
>University of Texas at Austin
>Austin, TX 78712-1086
>512-471-4206
>aduncan@mail.utexas.edu
Hmmm... Both your arguments are full of holes.
1. Many cats swim.
2. The argument that hominid hindlimbs "were about the same length
relative to body a size as is the case in modern chimps" is outdated. It
is largely based on the earlier work of Jungers. Many have disagreed
over the years (e.g. Wolpoff). Nonetheless, even Jungers can no longer
support this view. Jungers has changed his views and now argues that the
forelimb is isometric among humans and African apes - as well as Lucy
(Nature 369:194; AJPA Supplement 20:193). Therefore, because the
humeral/femoral ratio of LUCY is about 84, the length of her femur must
be relatively longer than that of a chimp. In other words, if humans,
chimps and Lucy all have the same length humerus (relative to body size)
AND the humeral/femoral ratios differ between these groups, THEN femoral
lengths, relative to body size, MUST differ between these groups.
Relative to chimps, Lucy's femur is long.
James C. Ohman, Ph.D.
Cleft & Craniofacial Center
The Johns Hopkins University School of Medicine
Baltimore, MD
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