Q. Dear Twig: Go on. What else might have made those great big Ice Age mammals go extinct?
A.: OK. Last week we looked at two of the four main ideas: the overkill hypothesis and the climate change hypothesis. (Go to http://www.ag.ohio-state.edu~news/story.php?id=4272 if you missed it.) Here are the other two:
The hyperdisease hypothesis suggests that humans or other mammals brought a new disease with them when they came to North America. The bug didn't bother the creatures that brought it. But it spread to new species — cave bears, ground sloths, etc. — and hit them hard. The animals hadn't faced it before. They couldn't fight it off. It might have wiped them out.
The combination hypothesis blames the die-off on multiple factors: disease, climate, overkill, more. Together they caused a snowball effect. One factor made another one worse. That one made a further one worse. And so on. The animals couldn't recover.
Next: Bring back the mammoth?
P.S. Q.: Why did the mammoth cross the road? A.: Teratorn's day off! Ha ha heeeee!
Notes: Sources included the American Museum of Natural History, http://www.amnh.org/science/biodiversity/extinction/Intro/GiantBeasts.html (click on "What happened to all these mammals?"); Ice Age Mammals of North America by Ian Lange (2002, Mountain Press Publishing Company); Twilight of the Mammoths by Paul S. Martin (2005, University of California Press); Mammal Evolution by R.J.G. Savage and M.R. Long (1986, Facts on File); The Call of Distant Mammoths by Peter Douglas Ward (Copernicus, 1997); and the BBC DVD "Walking with Prehistoric Beasts."
"Smart Stuff with Twig Walkingstick," published by The Ohio State University College of Food, Agricultural, and Environmental Sciences - specifically, by the Ohio Agricultural Research and Development Center (OARDC) and Ohio State University Extension, the research and outreach arms, respectively, of the College - is a weekly column for children about science, nature, farming and the environment. It's written at a 4th-grade reading level. For details, to ask Twig a question, and/or to receive the column free by mail or e-mail, contact Kurt Knebusch, CommTech, OSU/OARDC,1680 Madison Ave., Wooster, OH 44691, firstname.lastname@example.org, (330) 263-3776. Online at http://extension.osu.edu/~news/archive.php?series=science.