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Re: Early diets
Macintosh in computing cluster (finger@directory.yale.edu)
Wed, 25 May 1994 18:39:25 -0500
In article <60.941.7295.0N19F46B@canrem.com>, j#d#.moore@canrem.com (J.
Moore) wrote:
>
> > I have read that one of the differences between a herbivore and a
> > carnivore is the postioning of the eyes. Herbivores having eyes on the
> > sides of their heads for maximum field of vision to spot carnivores, and
> > carnivores having eyes on the front to give binocular vision and better 3-
> > d vision.
> > JON W. PARKER AlliedSignal Engines, Phoenix, Az
>
> But of course animals cannot be conveniently slotted into only those two
> categories. Many animals are omnivorous -- humans are, and so are apes,
> and it's overwhelmingly likely that early hominids were as well. In
> addition, some animals thought of and generally categorized as
> carnivorous are actually omnivorous, such as most (if not all) canids --
> all the various wild dogs, wolves, foxes, coyotes.
>
> Primates have eyes in front, yet are omnivorous, and that's omnivorous
> with a HUGE portion of the diet being plants.
>
Yes, it is true that primates today are generally omnivorous; but the
earliest primates (ca. 60-70 milliona yrs ago) were probably arboreal
insectivores. Forward-facing eyes would be beneficial for both dealing
with the 3-D nature of living in trees and for hunting insects. By the
time omnivory arose in primates much later their eyes were already forward.
In other words, the position of the eyes of primates arose for exactly the
reasons suggested above (hunting) and stayed that way because of
phylogenetic inertia.
Why didn't they revert to side-facing eyes to avoid predators? Primates
were still leaping around in the trees, so they needed the good depth
perception required to avoid falling 200ft from the canopy. More
importantly, primates use their hands for fine manipulation of objects more
than any other order of mammals. 3-D vision, along with opposable thumbs
and fingernails, is an adaptation for manual dexterity.
> [stuff deleted.]
>
> Point being: any claim that has you forced to choose between two and
> only two categories has probably got a big hole in it. Always look for
> a third category (or more); it almost always around.
>
Good point.
> Jim Moore
>
> * Q-Blue 1.0 *
Michael Seaman
seaman@minerva.cis.yale.edu
--
Posted/mailed from a Macintosh in a Yale University computing cluster.
Yale University assumes no responsibilities for either the content of this
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