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RE: Pleistocene/Holocene extinctions



> From: owner-DINOSAUR@usc.edu [mailto:owner-DINOSAUR@usc.edu] 
> On Behalf Of Brandon Pilcher
> Sent: Thursday, September 20, 2007 6:57 AM
> To: dinosaur@usc.edu
> Subject: Pleistocene/Holocene extinctions
> 
> 
> Sorry that this is not related to dinosaurs, but it does 
> concern paleontology, so here goes...
>  
> What is the most widely accepted and/or likely theory for the 
> mass extinctions in Eurasia, the Americas, and Australia at 
> the Pleistocene/Holocene boundary? Many people attribute them 
> to human overhunting, but my beef with this conjecture is 
> that Africa does not seem to have been affected nearly as 
> badly, even though African animals should have been the first 
> to go according to this model.
>  
> My opinion is that climate change was the most important 
> factor. The failure of many species to adapt to quickly 
> changing climate patterns seems more likely to cause so many 
> extinctions than a few primates with sharpened sticks.

Whew boy... Note that you are stepping here into a subject with a lot of
contraversy and acrimony. Seriously, this makes debates about T. rex
predation, the origin of birds, or dinosaur warm-bloodedness look pale and
tepid in comparison.

That being said, I happen to agree that the human predation hypothesis is
FAR stronger. The extinctions, when well dated, coincide stronger with the
arrival of humans (or sometimes a new human technology) into a region,
rather than climates. Indeed, the extinctions are highly asynchronous with
climate changes and with each other, but do line up nicely with human
migration around the planet.

Also, none of the climate shifts that happen near the extinctions are
statistically more severe than earlier changes experienced by the very same
species.

As for Africa and southern Eurasia: these animals co-evolved with humans
(Hominini) before they were humans (Homo sapiens), and so may have adapted
to the styles of this new predator. In contrast, the die offs in regions
where hominins were not earlier present tend to be more extreme.

Additionally, the patterns we see do not end with the New World extinctions!
Extinctions in Madagascar and the islands of the Pacific continue as
Polynesians migrated around the world in much more recent time.

But of course, because some of the animal extinctions may have been
associated with human predation and secondary effects doesn't mean that NONE
of them were due to climate change.

Thomas R. Holtz, Jr.
Email: tholtz@umd.edu   Phone: 301-405-4084
Office: Centreville 1216                        
Senior Lecturer, Vertebrate Paleontology
Dept. of Geology, University of Maryland
http://www.geol.umd.edu/~tholtz/
Fax: 301-314-9661               

Faculty Director, Earth, Life & Time Program, College Park Scholars
http://www.geol.umd.edu/~jmerck/eltsite/
Fax: 301-405-0796

Mailing Address:        Thomas R. Holtz, Jr.
                        Department of Geology
                        Building 237, Room 1117
                        University of Maryland
                        College Park, MD 20742 USA