Re: Where are the zoologists?
Phil Nicholls (email@example.com)
17 Dec 1994 04:54:59 GMT
In article <firstname.lastname@example.org>, loopy <email@example.com> wrote:
>In article <firstname.lastname@example.org>, email@example.com (Bryce
>> I could believe this if the feature was sometimes present, sometimes
>> not, for example blue eyes, inny-belly buttons, left-handedness, etc.
>> But for features which are dominant and universal throughout the
>> entire species, like the nose, hairlessness, adiapose fat, bipedalism,
>> etc. there needs to be an explanation.
>No, that's Joel's point. NOt everything needs or has an explanation. For
>instance Dawkins uses the example of the vertebrate eye. The photreceptor
>cells are wired "backwards"; that is, the light-receiving part of the cell
>faces the back of the eye, and the nerves come out of the cell at the end
>the faces the _front_. All vertebrates are wired this way. Why? is it
>because it was somehow advantageous? No, it is most likely there for what
>are known as "historical" reasons. It just happened that way, for no good
>reason, and since it was that way in our common ancestor, then all
>vertebrates have that eye structure.
Exactly! Actually the eyes develop from the telencephalon and the
position of the retinal ganglion cells are the result of the way
the cells are layered in the telencephalon. As you point out, this
is an historical constraint and is not adaptive in any way.
Similarly, the human pelvis is not a "rewired" chimpanzee pelvis.
Protohominids were very likely suspensory feeders and suspensory
feeders tend to be bipedal when on the ground.
Philip "Chris" Nicholls Department of Anthropology
Institute for Hydrohominoid Studies SUNY Albany
University of Ediacara firstname.lastname@example.org