Progress schmogress (was Re: competition)

["Tim Williams" <twilliams_alpha@hotmail.com>]

"KELL00BELL@aol.com" wrote:

> In a
> scenario of competitive replacement, the less adapted forms are >superceded 
> by better adapted ones (e.g. whales with increasingly >vestigial hindlimbs, 
> equines with fewer toes, hominids with bigger >brains) essentially as soon 
> as the latter arise.  There is usually no >discernible overlap, just a 
> succession of more advanced forms.  The >fact that this occurred in many 
> lineages of higher vertebrates >indicates that competition is the key 
> agency of extinction and >turnover.  Random physical factors would not have 
> favored progress so >consistently.


*sound of grinding teeth*

I see the quaint old 19th century notion of "evolutionary progress" is still 
rearing its head at the dawn of the 21st.

"There is usually no discernible overlap, just a succession of more advanced 
forms."

Well, this certainly didn't happen in birds.  _Rahonavis_, a basal avian 
that was strikingly similar to _Archaeopteryx_, was alive and kicking in the 
Maastrichtian.  Its droppings mingled with those that emanated from 
"advanced" avians, including the ancestors (or at least close relatives) of 
modern bird orders.

"...equines with fewer toes..."

Can we dispel this myth once and for all.  Equid evolution was _very_ 
complicated, and consists of more than just a smooth, simple continuum from 
little many-toed _Hyracotherium_ to big one-toed _Equus_.  This topic has 
been discussed *endlessly*, and was the subject of a whole chapter in 
Stephen Jay Gould's _Full House : The Spread of Excellence from Plato to 
Darwin_.  (Gould's discussion of the evolution of horses is one of the few 
things I actually agreed with in the book.)

"...hominids with bigger brains..."

Unless there's some hominid fossils you're keeping to yourself, I didn't 
think we knew enough about the evolution of this particular group to be all 
that confident in this assertion.  Sure, _Homo sapiens_ is the only 
surviving hominin species in the modern era - yetis and sasquatches aside.  
But can we be absolutely certain say that the hominin species we replaced 
had smaller endocranial capacities than our ancestors?

Rant ends.


Tim


------------------------------------------------------------

Timothy J. Williams

USDA/ARS Researcher
Agronomy Hall
Iowa State University
Ames IA 50014

Phone: 515 294 9233
Fax:   515 294 3163




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