Abstract

Did you know that the North American bison (aka American buffalo) was once an immigrant? Its ancestors migrated from Asia. But when? We recovered and dated new fossils and extracted their ancient DNA to find out.

We analyzed ancient DNA from the two oldest bison fossils known in North America: a foot bone about 130,000 years old that we found in northern Canada and an arm bone about 120,000 years old from Colorado. We also analyzed younger bison fossils from Alaska and northern Canada. We compared their DNA, which showed they were closely related and had a common ancestor. This meant that we could use their DNA to reveal the evolutionary history of bison in North America.

Our study suggests that the first bison arrived in North America 195 – 135 thousand years ago over a land bridge between Asia and Alaska. They quickly spread and evolved (changed) into different forms to adapt to their new environments. Their invasion was so successful that they became the dominant mammal herbivore in North America and even changed entire ecosystems. Millions of these large, powerful mammals lived in many parts of North America until their near extinction in the late 1800s.