Re: Human bottlenecks and bird taxonomy (was: Re: "Dinosaurs Died Within Hours...)

[Phil Bigelow <bigelowp@juno.com>]

Mickey Mortimer <Mickey_Mortimer111@msn.com> writes:
> Eric Martichuski wrote-
> 
> > More like 70,000 years ago (give or take).  But it's not as 
> suspect as you
> > might believe.


> Interesting.  Do any other species show evidence for such a 
> bottleneck at
> that time?


Good question.  The cheetah shows a bottleneck, but that may be a recent
(man-made) example.  Obviously, the best taxa to study are those that
share the same niche as early humans.  Mega fauna (large herbivores and
large carnivores) would be the best subjects for genetic study.  The
baboon genome may also offer up some clues.

It would also be helpful to find extinctions around that time.  A
Quaternary section of the appropriate age, with a rich micro-mammal
assemblage, would be ideal for such a study.  Are there any N. American
sites that contain the Toba ash layer?  It would make a great MS thesis.

FWIW, _H. neanderthalensis_ survived for another 40,000 years after the
Sumatra eruption (finally disappearing around 30,000 ya).  Whether
Neanderthals also underwent a genetic bottleneck around 70,000 ya
probably will never be known.  And why chimps did not suffer a bottleneck
at that time needs further study.

Distinguishing between simply "surviving" an extinction event (with no
reduction to the population), and getting genetically "bottlenecked"
during an extinction event (with massive loss in population) would be
useful.  Such a paleo study can only be achieved by studying
stratigraphic sections that contain abundant taxa (micro-fossils work
best).  Unfortunately, bird fossils are uncommon, even in the "richest"
sites, for such a study to work (my feeble attempt at dragging this back
to dinosaurs).

In the case of the human bottleneck, the most commonly accepted number
for the total human population after the "event" was 5,000 - 10,000
individuals.  More than likely, that total represents one breeding
population, not isolated populations.


<pb>
--





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