How much wood would a woodchuck chuck...

The tongue-twister about woodchucks could be asked of Castoroides ohioensis, the so-called giant beaver that inhabited North America during the last ice age, about 14,000 years ago.

The ice age animal was about twice the size of modern beavers, but, surprisingly, there is no evidence that the ice age beaver ate wood.

We are what we eat, and researchers from Michigan State University and the University of Wisconsin studied the isotopic composition of a jawbone of the ice age beaver and found that the ratio of carbon 13 to carbon 12 did not match that expected for an animal that ingested wood, but was closer to that of an animals that dined on aquatic plants.

The scientists compared the giant beaver to be, ecologically, “like little hippos.”

Source: Catherine Yansa, Geological Society of America Meeting, October 19, 2010

Geological Society of America Abstracts with Programs, Vol. 41, No. 7, p. 257

Reported by Perkins, S., Science News, November 21, 2009

Illustration (inset): giant beaver compared to modern beaver. From www.nature.ca

Irish Elk, revisited

The Irish Elk has long stood in textbooks as an icon for ice-age extinction.

The giant deer with the massive 12-foot-wide rack was thought to be extinct by the end of the last ice age; the most recent fossils of the Irish Elk had been dated to 12,000 years ago, but new discoveries in Siberia show that the Irish Elk was living there until about 7,000 years ago….4,000 years later than previous fossil finds indicated.

This new information implies that the extinction of the Irish Elk was not as abrupt as previously thought, and will add to the ongoing discussion of the factors that may have caused the extinction of the animal, climate change, disease, hunting.

Science News 6 November 2004, p. 34

See Nature, Oct. 7, 2004, Anthony J. Stuart.

Origin, Chapter 10, On the geological succession of organic beings

In this chapter Darwin discussed patterns of appearance and disappearance of species in the geological record.

Of extinction, Darwin wrote,

“The old notion of all the inhabitants of the earth having been swept away at successive periods by catastrophes is very generally given up. On the contrary, we have every reason to believe that species gradually disappear, one after another, first from one spot, then from another, and finally from the world.”

Darwin’s understanding of extinction followed from natural selection as the active agent, and it countered a Victorian-era notion that species had a definite duration fixed by some unknown natural law. Darwin wrote,

“We need not marvel at extinction; if we must marvel, let it be at our presumption in imagining for a moment that we understand the many complex contingencies on which the existence of each species depends.”

Pictured here: the Tasmanian wolf, Thylacinus cynocephalus. The last known wild Thylacine was killed in 1930; the last captive animal died in 1936.