[extropy-chat] Re: Human Evolution

[Robert Bradbury]

aperick, commenting on kevin's comments wrote:

> I want to know all the facts re primate hybrids.
> How many chromosomes does each have?

I thought there was a slight difference but I checked in Google.
Chimps and Gorillas have 48 chromosomes vs. 46 in humans.

> And what about other hybrid species, is the same number of
> chromosomes required for a live birth?

You might manage a live birth with and abnormal number or
mis-formed chromosomes.  Down's syndrome (trisomy 21)
comes to mind.  There are others (humans can apparently
survive with trisomy 21, 18, 13 and 8).  But the consequences
may be quite significant.  [Google: trisomy syndromes].

We do not know enough to reliably predict in any way the
results of an untried cross breed.  But for cases where there
is an extensive amount of work (e.g. plants) there may be
enough knowledge to make an educated guess as to whether
it will work.

It remains (to my knowledge) a mystery in biology the
specific requirements that allow the development of new
species.  This may involve simple chromosome rearrangements
or in the more difficult cases an increase or reduction in the
number of chromosomes.  Increases or reductions probably
make reproduction much more difficult and so those lines
in most cases die out.

The technology for chromosome mapping is now relatively robust.
So we can look at human chromosome segments and know what
mouse chromosome segments they match up against.  So even
though humans and mice are separated by many tens of millions
of years of evolution we can look at the genomes and know
that in the process of evolution "this went here and that went there".

Probably sometime later in this decade or early in the next decade
someone will try to backtrack this information and assemble
the proto-genome for mammals.  After that attempts at the
assembly of the proto-genome for older higher level organisms
(reptiles, fish, etc.) will probably be attempted.  There is a
lot of room for graduate students making a mark for themselves
in attempting such reconstructions.

So -- I would not be surprised at all if we could eventually
recreate the Neanderthals, the Mammoths and eventually
the Dinosaurs.  We might even be able to recover what
was lost after the Cambrian Explosion.

Robert