Before there were humans in what is now North America, there were bison. Millions of bison who were witnesses to the
invasion migration of these previously unknown creatures who eventually were responsible for their near extinction. While today’s humans speculate that their ancestors traveled to the Americas via a long-gone ice-free land mass in what is now the Bering Strait, the bison knew better. Today, their DNA tells a different story.
Two independent teams of researchers looked at DNA collected from ancient bison bones as well as from the remains of plants and other animals to determine how the Clovis people, the assumed first settlers of North America, arrived. In their study published in the journal Proceedings of the National Academy of Sciences, researchers led by Peter Heintzman and Beth Saphiro of University of California found minor variations between the DNA of bison in Alaska and North America, suggesting that they were separated for a time 23,000 years ago by the merging of glaciers. An ice-free corridor re-opened 13,000 years ago, allowing plant-eating bison and bison-eating humans to migrate south.
Wait a minute. Fossils of the Clovis people show they were already present 13,000 years ago, which means they must have taken another previously unknown route. Heintzman’s team agreed and a study published in Nature confirmed it. Researchers led by evolutionary geneticist Eske Willerslev from the University of Cambridge found that there was not enough vegetation in the corridor to sustain bison and human life until after 12,600 years ago and a livable forest didn’t appear until 10,000 years ago.
So how did the Clovis and possibly pre-Clovis people get here? Both teams suggest they came not by land but by water. Instead of waiting for the glaciers to melt, they may have traveled along the Pacific coast in the chilly but not frozen Pacific Ocean.
What do the bison have to say about this? Nothing yet, since it’s still a theory proposed by many besides the authors of these studies. However, this new technique of looking at the DNA of an entire genetic landscape rather than individual species may one day provide the answer, says Willersley.
Instead of looking for specific pieces of DNA from individual species, we basically sequenced everything in there, from bacteria to animals. It’s amazing what you can get out of this. We found evidence of fish, eagles, mammals, and plants. It shows how effective this approach can be to reconstruct past environments.
If the bison had known what these humans were capable of, would they have pushed them back into the water?