The environment encountered when the first people emigrated into the New World was variable and ever-changing, according to a Penn State geologist.
"The New World was not a nice quiet place when humans came," says Dr. Russell Graham, associate professor of geology and director of the Earth & Mineral Sciences Museum.
Archaeologists agree that by 11,000 years ago, people were spread across North and South America, but evidence is building for an earlier entry into the New World, a date that would put human population of North and South America firmly in the Pleistocene.
"We want to know what it was like back then," says Graham. "What did they have to deal with?"
There's not a whole lot in the article unfamiliar to the post-Pleistocene extinctions issue, but it summarizes the climate-controlled-extinctions argument pretty well.