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

[Eric Martichuski <herewiss13@hotmail.com>]

> From: Mickey Mortimer
>
> Surely you meant much more recently, and the story itself looks suspect to 
> me.

More like 70,000 years ago (give or take).  But it's not as suspect as you 
might believe.  The estimated date for the genetic bottleneck in our 
ancestry coincides nicely with the super-volcanic explosion of Mount Toba, 
near Indonesia (71,000 years ago).  And I'm using "supervolcano" in the 
sense that Yellowstone National Park is basically one _huuuuuge_ caldera.  
Mount Toba sent up around 800 cubic kilometers of ash.  Tambora (largest 
historical eruption) only emitted 20 cubic kilometers.  Mt. St. Helens was 
only a measly 0.2.

Within the past 450 million years, we know of only one eruption that was 
larger.

Paleoclimatology studies say that Toba caused 6 years of near total winter, 
and the next millennia was the harshest period during that ice age.

We know humanity went through a bottleneck.  Such an eruption is going to 
_severely_ impact human populations (along with all other sorts of 
populations).  Tiny, scattered populations facilitate the rapid divergence 
into "races" that we see occuring in the fossil record around 50,000 to 
75,000 years ago.

It's all circumstantial evidence, to be sure...but extremely suggestive 
nonetheless.  Googling for "human, genetic bottleneck and volcano" gives you 
a lot more info on the subject.

And, beyond all that, it _must_ be true because I saw it on the Discover 
Channel! ;-)
___________________

Having shed a little light on that subject, I've got my own taxonomic 
question relating (tangetially) to the bird/dinosaur definition debate:

Why did Linneaus, et. al. choose the Gryphon vulture as an exemplar?  The 
ostrich, as a highly divergent out-lier, I can understand.  And I have near 
total ignorance concerning Tinamous.  But are vultures _really_ so unique as 
to merit serving as one of the brackets of their entire clade?  And why the 
Gryphon vulture?  Just an random choice by Linneaus?

It all seems so very arbitrary.

Eric
______________________________________________________________________
"There is no other wisdom,
And no other hope for us
But that we grow wise. -- Diane Duane
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