Re: tree-climbing hominids

chris brochu (
11 Oct 1995 14:27:57 GMT

In article <> H. M. Hubey, writes:
>>I can't believe I am actually responding to this.
>Neither can I?

Nor I.
>>Evolution does not have a direction.
>Of course it does. It has one now and it's pointing in that
>direction. If we knew more we'd be able to point in the
>right direction. Actually I think some geneticists actually
>think so too and would be willing to start.

YAAFI (Yet another argument from ignorance)

Selection may have "directionality" at any point in time, but phylogeny
is not "directed" toward some ultimate goal. Tail feather length may be
selected for in a population of birds, but only because there is an
immediate benefit for having longer tails than those of your neighbor,
not because you want your descendents in n generations to have outrageous

>Direction implies some idea of
>>where you are going and some implication that once started the
>>motion cannot be changed.
>Direction doesn't imply anything about knowing which way to
>go. If you want to define the word this way, then it's your

Agreed. But the way you're using it implies the definiton you reject.

>Evolution is a random process of mutation and
>Mutation doesn't have direction if the density function is
>symmetric. If not it has a direction. Selection certainly
>has a direction.

See above. This is a correct assessment. But, as stated above, there is
a big difference between immediate selective direction and phylogenetic
trajectory over geological time.

>Just because an organism has gone so far in one direction
>>does not mean that you can extrpolate future developments.


>I can understand why you would want to defend this point of
>view. If you don't we'll ask you to show the scientificity
>of your science by making predictions.

DOH!.... (YAAFI)

"Predictability" in science does not necessarily operate at the level of
the process - it should also be valid for observations.
Paleoanthropologists have a model that predicts the presence of early
hominid remains, with tree-climbing ability and modest brain size, in
woodland habitats. So far, this prediction has held. If something wierd
were to turn up, we would have to amend our hypothesis.