evolution archive list

Tim Ikeda (tikeda@sprintmail.hormel.com)
Thu, 27 May 1999 23:31:31 -0400

Berthajane Vandegrift writes:

[intro removed...]

> Question no. 1:
This has been addressed by others...

>Question no 2:
>Since there is great uncertainty about how mutations of macro evolution
>arose, how can anyone be certain they were "random"? Isn't an insistence
>upon "randomness" merely a question of ideology, reinforcing the suspicion
>that Darwinism has become an anti-theist religion?

"Randomness" is, at its core, a philosophical question and can
apparently be worked into theistic and atheistic worldviews.

> Question no 3:
> I've heard "common ancestor" written in the plural, conceding the
> possibility of more than one. If there could be 2, or 5, or 10
> common ancestors, why not 100--or 1000?

I haven't seen "common ancestor" written in the plural. I suppose
one alternative would be that life arose multiple times and some
lineages "fused" into hybrids -- These hybrids then lucked out and
became the only branch to survive. I suppose that scenarios is
possible but I suspect that this would have to have happened very
early in the history of life. I make this guess on the basis of
the tremendous genetic and biochemical similiarities we see in life

> Where would biology set the limit? Does one common ancestor
> insist that life arose only once

No, only that arose _at least once_.

> --and everything descended from that one unique event?

Yes, by definition. Everything alive _today_ descended from a
common ancestor. For example, it might be possible that life
arose twice but only one lineage survived.

> What if life is discovered to be common in the universe? Similar DNA
> apparently results in similar morphology, but is that necessarily
> proof of common descent?

Given what we know of mutation, reproduction and variation, I think
that for most formulations of common descent, this would be a
necessary pattern. But the pattern may not be exclusively produced
by common descent.

Note - "Different DNA" also may result in similar morphology.

> Question No.4:
> Rich Daniel asks: "If there is a vast gulf between humans and chimps,
> where else could it be but in the genes?" What is wrong with "we
> don't know"? I've read that a population of fruit flies can be
> bred without eyes. However after a few generations the genes for
> eyes reappear. Wouldn't that suggest there might be something more
> involved than genes?

Can't tell without a better description of the system...
The "genes for eyes reappear" or the eyes reappear?

> Isn't the insistence that instincts and behavior are specified in
> the genome based upon the fact that we merely don't know what else
> might control them? Is there any reason to believe a "alltruism
> gene" exists--other than faith that there is a gene for everything?

There is no "gene for everything", but I understand what you mean.
However, the existence of extra-genetic factors is not necessarily
incompatible with selection & evolution. What is means is that
additional mechanism are involved.

> Question No.5:
> New genes are sometimes said to be the result of gene duplication.
> (transposons)

Transposons are mobile genetic elements. Often they do
duplicate during "transit". But "gene duplication" simply
describes an event where a copy of one sequence is made --
Transposons may have nothing to do with it. Gene duplication
is but one means by which new genes can made.

> The duplicate gene "decides" or "is recruited" to perform a new
> function. Is anything really explained by that language? What or
> who does the "recruiting"? (Sounds supernatural to me.:-))

Beware of the implied teleology of those words. "Decides" is
improperly used here -- Maybe you heard it as a sloppy slang
used by biologists who attach a slightly different meaning
to the word.

"Recruitment" is not too bad. That alludes to the contingent nature
of variation/selection. A simplistic example: A new variation
arises with altered functions. One of these functions provides
a selective advantage. It gets propagated as a result and
further rounds of variation/selection result in a gene that
provides this new function better. One might say that the old
gene was "recruited" for the new function. Life does the recruiting.

Tim Ikeda
tikeda@sprintmail.hormel.com (despam address before use)