The finding that a 24,000-year-old child from Siberia carried ancestry related to modern Native Americans was recognized immediately as a significant result that would change how researchers thought about the peopling of the Americas.

The Age Estimation And What It Means

The radiocarbon dating of MA-1 deserves specific attention, because the number — 24,000 years before present — is the kind of figure that can be stated easily but is harder to establish rigorously than it might appear.

Accelerator mass spectrometry, or AMS, radiocarbon dating works by directly counting the atoms of carbon-14 in a sample, rather than measuring the decay of carbon-14 through its radioactivity.

AMS requires much smaller samples than conventional radiocarbon dating — typically a few milligrams rather than grams — and is correspondingly more precise.