What caused the explosion was the skull.

When James Chatters described the morphological features of the skull in his early reports, he used language that was cautious and technical.

He noted the long, narrow shape of the cranium.

He noted the projecting face.

He compared these features to certain population groups around the world — not Europeans specifically, as had sometimes been misreported, but to what physical anthropologists call “Archaic Caucasoids” or, more simply, to populations with certain shared skeletal characteristics that differ from those typically seen in modern Native American groups.

To understand why this distinction matters, you need a brief excursion into the science of physical anthropology and what it can and cannot tell us.

Physical anthropology has long attempted to use skeletal features to identify population ancestry.

The underlying assumption is that different human populations, through thousands of years of living in geographic isolation and selective pressure, developed certain characteristic skeletal shapes.

By studying enough skulls and comparing enough measurements, anthropologists developed systems for estimating the likely geographic ancestry of an individual’s skeleton.

The problem — and it is a serious problem that many researchers have grappled with extensively — is that these categories are imperfect, contested, and shaped by historical assumptions about race that may not reflect biological reality.