Discovering Ancestry

Since DNA is passed down from parent to offspring, relatives share DNA sequences. Applying this same principle to a larger time scale, individuals of common descent (i.e. shared ancestry) also share DNA sequences. The genomes of any two individuals on earth are over 99% identical. However, since our genome is 3 billion nucleotides long, even a 1% difference corresponds to millions of nucleotides. Modern genetic technology is capable of identifying this 1% and recognizing particular sequences that are specific to different populations around the world.

A table with four squares and three rows.
Image courtesy of Jane Ades, NHGRI

Genealogy addresses the probability of shared ancestry between people and possible biogeographical origins, and this field has been enhanced dramatically by the advent of DNA testing. All human population groups share common ancestry that most likely originated in Africa with the earliest pre-hominid populations. As human migration continued throughout the world, genetic variation arose among populations via mutations. Because early migratory populations were often isolated from other groups, there was limited mixing, and the mutations stayed unique to the groups they arose in. These genetic “signatures†can still be found in certain indigenous populations around the world that have had limited interaction with outside groups. Efforts by researchers to identify and map these genetic markers now make it possible for anyone to explore their ancestry. For example, with just a cheek swab, you can learn about the migratory patterns of your ancient ancestors through participation in National Geographic’s Genographic Project.

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