Re: local evolutions

Philip Nicholls (pnich@global2000.net)
26 Aug 1996 11:43:59 GMT

Yousuf Khan <ykhan@achilles.net> wrote in article
<4vn388$s6n@hermes.achilles.net>...
> On Thu, 22 Aug 1996 09:35:48 -0500, "C. Marc Wagner @
UCS"
> <mwagner@indiana.edu> wrote:

> >I think that this theory has begun to fall out of favor
in recent years
> >as genetic evidence has come down on the side of the
"Out of Africa"
> >theory that several times in the past Hominids have
migrated out of
> >Africa. If I understand it correctly, the genetic
evidence suggests
> >that all living Homo sapiens sapiens are descended from
a single female
> >who lived around 800KYA. Much later than Homo erectus
left Africa.

> However, what evidence is there that it did originate in
Africa?
> All we can guess at is how long ago it happened, but that
doesn't
> tell us where it happened: it could've happened in
Africa, but
> not necessarily so.

So far, the oldest hominid fossils to show anatomical
changes consistant with the emergence of modern Homo
sapiens come from Africa. These changes include an
increase in the height of the forehead, a rounding of the
back of the skull and a thinning of the bones that form a
cranial vault.


> Anyways, I believe that erectuses were just a different
breed of
> sapiens, and perhaps with the flow of genetic material,
gradually
> over time, the one genes that gave us our larger brains
became
> the fashionable trend among humans (much like blonde hair
seems
> to be desired by many now), and the gene got passed back
and
> forth over the human populations until our brains were
much
> bigger. And it still doesn't preclude an origin of that
> particular gene about 800KY ago (as you said), it just
> establishes a timeline for when it began to happen.

Leaving a debate on the species problem asside for the
moment, not all human groups find blond hair to be that
attractive. I think that if we look at the whole hominid
fossil record around 150,000 years ago we see a great deal
of morphological diversity. I think if we were dealing
with any other species they would have quickly been
classified as different paleospecies.

I think the current fossil record fits nicely into a
punctuated equlibirum model. The increased diversity,
followed by the emergence of Homo sapiens sapiens
represents a punctuational event.

>
> >Other studies suggest that genetic diversity among
Africans is much
> >greater than among non-Africans, also supporting a
"recent" migration
> >"Out of Africa."
>
> What exactly do you mean? How do you measure genetic
diversity?

I think he means diversity in the mDNA of Africans vs
Non-Africans. This is the evidence cited by mDNA people
of a population bottleneck and African mDNA being older
than other populations.

-- 

Phil Nicholls                                          " To

ask a question

pnich@global2000.net                        you must first

know

                                                           

        most of the answer."

                                                           

              -Robert Sheckley