At Home in the Ice Age
When snowstorms closed my road for the third time in a new year merely six days old, the only thing to do was to throw another log on the fire and curl up with a good book. Christmas brought perfect reading material for such weather: E. C. Pielou's After the Ice Age published by the University of Chicago Press.
It seems unlikely that someone who works at the Geophysical Institute would turn to an outside expert for information on the era of great cold. In the institute are scientists like David Hopkins, probably the world's expert on the Bering Land Bridge, and Carl Benson, a most knowledgeable source on glaciers and snow (and the author of the exuberant song Ice is Nice star of the institute's annual Christmas party) among many others. But Pielou brings a different perspective. She's a biologist, and her book is subtitled The return of life to glaciated North America. She's also willing to make things obvious for the uninformed.
For example, I'd never thought of ice-age Alaska as harboring antelope, which I think of as African animals. Mammoths lived here; so did very hardy people. Thanks to the display at the University of Alaska Museum, I know ancient long-horned bison lived in interior Alaska, and so did a kind of lion that preyed on the Bison. From Pielou's book, I now know about other Pleistocene mammals that crossed over the freeze-dried Bering Strait. One kind of antelope, the saiga, was among them. This spike-horned animal stood about as tall as a big malemute dog. It had a rounded, Roman-nosed profile, so that---judging by artists' reconstructions---the saigas of Beringia had an essentially goofy look to them.
Saiga antelopes deserve the past tense only on this side of the Bering Strait. Their fossilized remains have been found near Fairbanks, but their living cousins still graze the steppes of central Asia. Unlike the bison and other mammals of the time, saigas never traveled down the southward-leading corridor between the great Laurentide ice sheet of interior and northern North America and the Cordilleran ice sheet of the Pacific slope.
Which brings up another useful aspect of Pielou's book: she writes about things that geologists or glaciologists might assume a reader would already know. From the case of the saiga antelope, and with a nod to UAF paleontologist Dale Guthrie's work on the evolutionary history of bison species, Pielou shows that the path down into North America opened and closed in pulses. Furthermore, when that path was ice-free and passable, probably the Bering Land Bridge was under water. Animals, including people, could come on to this continent from Asia when the land bridge was dry---and easily, since its area was greater than that of Alaska. But then they might have to wait around for years until the ice pulled back from the corridor.
It's all a matter of where the water was. When enough of it fell onto the glaciers and froze there, sea level would go down; there wasn't enough liquid water to fill the oceans to the extent we know now. The Bering Strait would become a part of the broad Bering Land Bridge, high and dry and easy for hardy animals to cross. But all that ice added to the sheets meant they could swell and push together, closing the corridor leading down the continent.
Less water frozen into the ice meant more would be available to fill the seas, which then would wash over the land bridge and close the path to Asia. Of course, there'd be less ice swelling the ice sheets, so the way into the Americas would open to wandering animals. The saigas never bothered with that last trek. Perhaps they just got tired of waiting, turned around and went back home.
I can relate to that. It's still snowing here.
