What Basal Really Means

The word basal is one of the most important terms in the USR1 story, and it is also one of the most easily misunderstood.

In a phylogenetic tree — a branching diagram that represents the evolutionary or population genetic relationships between groups — basal means closer to the root.

When researchers say that USR1 is basal to other Native American populations, they mean that in the family tree of Native Americans, the branch leading to USR1’s lineage diverged before the branches leading to other sampled populations.

This does not mean that USR1 represents an older or more primitive form of humanity.