Bones from mastodons move back dates of human migrations

Usually bones tell us about the animal that used them when it was alive. Sometimes they’re more informative about a third party, especially when unusual damage or locations are involved. Around 30 years ago, a mastodon rib was found in Washington state with a bone spear-head lodged in it. New analysis reveals not only that the spear was mastodon bone as well, but that human hunting activity was present in North America at least 1000 years earlier than one of the leading theories of human migration to the region.

Examining the bone in the bone

The bones were examined on a number of fronts to put together the story of this felled mastodon. Standbys like Carbon-14 dating, in which the amount of the undecayed isotope is measured, was a key part in determining the bones’ age of 14,000 years old. Since these bones were not yet fossilized, their DNA could be examined in addition to some proteins being sequenced. While knowing the identity of the spear-head “donor” is of interest, the standout finding from all this testing is the age of the materials.

Rewriting human-migration history

For many years, archaeologists theorized that the first peoples in North America arrived around 13,000 years ago. Discoveries in Clovis, New Mexico sparked what was known as the “Clovis First” theory, wherein all subsequent groups of humans in the Americas were thought to have been offshoots of this original settlement. This spear-head, along with a growing list of other discoveries in the last few years, have basically overturned that theory.

By moving the timeline back on when humans arrived in North America, we also have to reconsider models of how mega-fauna like mastodons went extinct. If the Clovis theory had held, it would have meant that the arrival of humans led to the immediate and seemingly aggressive elimination of large mammals on the continent. A thousand extra years on the continent doesn’t excuse humans’ role in these animals’ extinction, but it does allow for a more gradual and less extreme interaction, possibly with more room from influence from factors like climate change.

Source: Tracing the first North American hunters, University of Copenhagen