Wednesday, April 1, 2009

Extinctions, Previous and Present

Last night, Nova had an episode titled Last Extinction. You can probably tell by the title of this post that I didn't think much of their title. And honestly, I didn't find the program that compelling either, but I am fascinated by the subject of what caused the geologically sudden disappearance of North American megafauna such as mammoths and mastodons and sabertooth cats and sloths and camels and glyptodonts approximately 13000 years ago after they'd dominated the continent for 100,000 years. I don't know about you, but I'd love to see a woolly mammoth while strolling through a snowstorm like the one we had yesterday (thank you, weather gods, for one last (?) Superior storm).

You can get a good introduction to the subject here, particularly by reading "End of the Big Beasts" and "The Extinction Debate". There are several theories attempting to explain the extinction. The most widely accepted is that newly arrived humans hunted them to death, and I'm waiting for an interlibrary loan book titled Twilight of the Mammoths which seems to be the primary book available on the subject
for the general public and which supports that theory.

Lord knows I'm not a big fan of humans who have certainly eliminated plenty of other species, but I find it a little hard to completely accept that a relatively small number of humans (who apparently disappeared at the same time) with primitive weapons wiped out a continent's worth of a dozen or three species in a short period of time. Other theories include climate change, disease, and that which this program explores, a comet strike. The main evidence supporting this is a layer of tiny diamonds found in a glacier.

The book I referred to above is subtitled Ice Age Extinctions and the Rewilding of America, and the references include Dave Foreman's book Rewilding North America. If you'd like to hear a lecture Foreman gave last week on the subject, you can listen here. Foreman talks about those and more recent extinctions, the fact that human population has tripled in his lifetime, the effects of the absence of large carnivores, and reads from Aldo Leopold (and I'll point out again that the turning point in what Foreman calls the most important conservation book is not a vision of continental wilderness or a scientific respect for ecosystems and species, but the look in the eyes of one individual animal). The lecture's conclusion is a fine rejoinder to those who insist that deep ecology is all about hatred and misanthropy--it's about joy and connection.


Allan Stellar said...

Thanks for the Foreman link!

Thanks for this post. I don't buy the theory that those who crossed the land bridge took out the large mammals of North America. Doesn't make sense to me. Although I'm no expert. Just seems there were too few humans and the those who went extinct did so very, very quickly. A virus brought over the land bridge?

greentangle said...

I don't know enough about it to make a guess, but it doesn't seem to me there's enough conclusive proof to call any of the options more than a guess with arguments for and against.

Extinctions certainly happened in smaller isolated areas when humans arrived but my main objection to the overkill theory in NA is the same as yours: how many people could there have suddenly been in this vast continent, and even if they killed off all the life in an area and then moved on to the next area, wouldn't the animals then have repopulated the vacated area?