DNA testing has made tracing family trees into a common past-time for our globalized world, but according to one mathematician, we might be overthinking it.
Joseph Chang, a statistician at Yale University, applied statistical modeling to find the most recent common ancestor of all humans on earth. His model, using the number of ancestors of each individual as well as current population size numbers to calculate the point at which all possible family bloodlines converge. He finds that it was a lot more recent than we think.
For those of European ancestry, the most recent common ancestor lived 600 years ago — making him/her a contemporary of Johannes Gutenberg (1400-1468), the inventor of the printing press. Expanding from Europe, the most recent common ancestor of everyone alive today walked the earth in 1400 B.C., or 3,400 years ago — and, taking migration patterns into account, likely lived in Asia.
The number of ancestors that each person has grows exponentially the further back that we go. Everyone has two parents, four grandparents, eight great-grandparents, and sixteen great-great-grandparents, and if you follow that back a thousand years, or approximately forty generations, everyone has over a trillion direct ancestors.
Except that the total number of humans that have ever lived doesn’t come close to a trillion people, so this only makes sense when we remember that our ancestry is shared.
Chang concludes his research thus:
“Our findings suggest a remarkable proposition: No matter the languages we speak or the color of our skin, we share ancestors who planted rice on the banks of the Yangtze, who first domesticated horses on the steppes of the Ukraine, who hunted giant sloths in the forests of North and South America, and who laboured to build the Great Pyramid of Khufu.”
Not that this make genealogy obsolete or irrelevant. Math may prove that we are all descended from one person, but the questions of how that lineage has been passed down over the years and the details of our ancestors’ lives are still open to inquiry.