Kurt Abbott BestulI am your cousin#
Last tended 2026-07-05
At the risk of stating the obvious, if you are a living human reading this (not a bot or an AI agent) then I am your cousin—absolutely regardless of how different your pedigree may seem to be from mine. It is the simple result of a concept called pedigree collapse, and it bears reconsideration any time one person regards another person as "other."
When I say, "I'm Norwegian, German, and English," it stems from me looking back roughly four generations to great-great-grandparents (second great-grandparents) who immigrated to the U.S., and looking back ONLY that far.
If I were to instead look back 30 generations (roughly 800 to 1,000 years), the math becomes deeply counterintuitive. That counterintuitive state arises from exponential math versus finite populations.
Exponential math: the exploding family tree#
To calculate your ancestors generation by generation, you simply multiply by 2 every step you go back:
- 2 parents
- 4 grandparents
- 8 great-grandparents
- 16 second great-grandparents...
Seems sensible enough, right? If you keep running this math back to around 1000 CE (roughly 30 to 33 generations ago), the number of ancestor slots in your tree hits 8.5 billion.
But there is a massive problem: in 1000 CE, the entire population of Europe was only about 25 to 30 million people.
How do you fit 8.5 billion ancestor slots into a continent containing only 30 million people?
Because the number of our ancestors doubles every generation (\(2^n\)), a person living today theoretically has over 1 billion ancestor slots open in their family tree at the 30-generation mark. Since that 1 billion is more than the entire population of the Earth at the time, those slots must overlap. Enter pedigree collapse: it means we are all deeply interconnected. Go back just 1,000 to 2,000 years, and you reach a point where anyone living then who left any surviving descendants is an ancestor to everyone living in that geographic region today.
Finite populations: Pedigree Collapse (the reality check)#
The only way the math works is if those slots are being filled by the same people over and over again. This is called pedigree collapse.
If you go back 1,000 years, you aren't descended from millions of distinct, independent bloodlines. Instead, your family tree stops looking like an expanding triangle and starts looking like an intricate, tightly woven mesh network.
THE ILLUSION (Continuous Expansion) THE REALITY (Pedigree Collapse)
[ You ] [ You ]
/ \ / \
[Parents] [Parents] [Parents] [Parents]
/ \ / \ / \ / \
[...] [...] [...] [...] [...] [...] [...] [...]
/ \ / \ / \ / \ \ / \ / \ /
[ Billions of Ancestors ] [ Family lines merge ]
\ \ / /
[ Small Pool of Ancestors ]
You might have a single grandmother living in 1000 CE who fills 100,000 different slots in your family tree because her descendants married her other descendants over the centuries. In a small, historically isolated or regionally dense population (like medieval Europe), everyone was essentially marrying a distant cousin without knowing it. This is the basis of the "Charlemagne is everyone's distant grandparent" trope: for anyone with even a shred of European ancestry, this pedigree is, in fact, a hard mathematical and genetic reality.
The all-or-nothing rule#
Statisticians and geneticists (like Joseph Chang at Yale) modeled this network effect using probability theory. They discovered that in any closed or semi-closed population, as you move back in time, individual family lines mix so thoroughly that the 'branches' collapse back into a single 'puddle.'
Because of this intense mixing, when you look at the population of Europe in 1000 CE, the people of that population fall into exactly two categories:
- The Dead Ends: people whose children died out, or whose grandchildren didn't reproduce. They have zero descendants today.
- The Ancestors: people who had children, who had children, who had children, surviving all the way to the present day. Because the web is so tightly interconnected, their DNA spread into the entire pool.
There is no middle ground. A European living in 1000 CE cannot be the ancestor of just your neighbor but not you. If their lineage survived the wars, famines, and plagues of the last millennium to reach the modern era, their genetic footprints have expanded to cover the entire continent.
And then there's the Afro-Eurasian Isopoint#
If we continue past the European convergence (which applies to me) and also scope in Africa and Asia (every person presently living whose ancestry maps back to these three connected continents), my line begins to interweave with that entire population through history's massive, ancient trading routes and migrations. At somewhere between 2000 and 5000 thousand years ago, I share a complete, identical ancestral pool with every human being currently alive whose pedigree is of those continents. At that isopoint—lets arbitrarily call it 2500 years ago—all of those living cousins share distant grandparents in Rome, Egypt, Persia, and China.
More cousins: the Global Isopoint#
In the 15,000 to 20,000 years ago range: my 'tree' finally hits the true Global Isopoint. The lines reach back far enough to meet the populations before they crossed the Bering Land Bridge into the Americas or navigated out to distant Oceania.
If, instead of setting my threshold at my great-great-grandparents who immigrated from Norway, I reach back to a grandparent in that time range, then absolutely every living person anywhere on the planet is my cousin.
Consider the timeline of the modern brain#
Now a look at the important components of being an optimally functioning human at ANY of these isopoints...
We have to go back in the range of 100,000 to 50,000 years ago to reach what anthropologists call Behavioral Modernity. This is the point where the neural "wiring" or architecture of the brain achieves its modern state. Suddenly, humans everywhere start producing complex art, musical instruments, structured burials, and advanced tools.
By 50,000 years ago, the biological evolution of the human brain's raw cognitive capacity essentially plateaued. Since then, human history hasn't been a story of biological upgrades, but of cultural and technological software updates running on the exact same ancient hardware. Let me restate that: you and I, and every human presently living, are a 50,000-year-old model of human.
Any baby born at any point more recent than 50,000 years ago—long pre-dating either of the isopoints I mentioned, let's pick a birth year of 200 BC—had the exact same neural plasticity we do. If we were to time-travel that newborn into the loving arms of modern adoptive parents in the U.S., it would adapt to English syntax, digital screens, and mathematics just as easily as it would have adapted to Celtic farming techniques or Roman military discipline. The brain simply wires itself to whatever stimulus it receives in the first few years of life.
Cousins and alike#
So the facts are that we are cousins—relatives—one and all, and we are profoundly alike in our human hardware and capability. These are strengths we would be wise to marshal as we take on the millennium's major challenges.
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