Re: Neoteny was Re: god makes hubey
chris brochu (email@example.com)
26 Nov 1995 01:51:14 GMT
In article <firstname.lastname@example.org> H. M. Hubey,
>>Another misconception regarding heterochrony is apparent here - animals
>>are not heterochronic. Characters are. Some aspects of adult human
>Animals are comprised of their characters/characteristics. Of course,
>I only picked on a few observable with the naked eye. But so what,
>a whole "science" has developed around bone-gazing. Why is it
>not legal when I do it?
It's your methodology to which I object. Organisms are, indeed,
comprised of characters. But it does not follow that an organism is its
characters. Characters can be described as heterochronic
transformations, but organisms cannot. It is true that some lineages
(e.g. plethodontid salamanders) are more prone to one kind of
heterochrony over another, but that does not render an individual
>>morphology are paedomorphic (or neotenic, if you prefer that word)
>>insofar as they are more similar to what we see in early ontogenetic
>>stages in other primates.
>I wasn't discussing the fetal stage.
Neither was I. I said "early ontogenetic stages." This could refer to
anything between conception and adolescence.
It does seem as if there's
>some kind of an order there, as is told of those about to die;
>their lives are supposed to flash by quickly.
>If this process were to continue linearly, then babies would
>still resemble earlier life forms, so chimp babies would look
>say, doglike. But it's the reverse; they look more like humans.
>How do they foresee this?
I think it's on this point that you fail to grasp heterochrony. I
recommend reading the works of Von Baer - or, for simplicity, a good
summary of his writings, for example E.S. Russell's "Form and Function."
Von Baer's principle stated that during ontogeny, characters appear from
"less general" to "more general." SInce Von Baer was not an
evolutionist, he didn't phrase his writings in transformational context,
but we would now restate his law as trending from "primitive" to
"derived." Thus, early embryoes of sharks, bony fishes, salamanders,
dogs, chimps, and humans all look very similar because they possess
characters common to all vertebrate embryoes. As development progresses,
characters appear sequentially that are held in common with close
relatives. Characters thus appear in the bony fish, salamander, chimp
and human that do not appear in the shark embryo, and later on the
salamander, chimp, and human similarly diverge. This has been misstated
by many, following Haeckel, as though we pass through a "fish" stage, an
"amphibian" stage, and so on during ontogeny, but this is untrue.
Chimps and humans look similar as infants because we are close relatives,
and some characters shared in common will appear early in ontogeny.
Chimps, humans, and dogs do look similar during embryology (we are all
three eutherians), but the chimp and human will look more similar because
of our ancestry. There is no "foresight" involved, and even D'Arcy
Thompson would argue against such a deterministic view.