Our Overlapping Family Trees

“If I did not believe that anthropology could also serve as an instrument of peace and a tool for human conviviality … I would have long since renounced this uncomfortable and difficult science and somewhat marginal way of life.”

— Nancy Scheper Hughes, “Saints, Scholars, and Schizophrenics” (2001: 53)

“One sunny mornin’ we’ll rise, I know/  And I’ll meet you further on up the road.”

— Johnny Cash, “Further On Up the Road


I thought it might be helpful to visualize just how quickly the number of direct ancestors can grow, and how we can confidently say that all people share ancestors. Let’s say that this is your biological family tree for a just a handful of generations, keeping in mind that ‘family’ here refers to direct biological ancestors. This might not exactly be the family you recognize during holidays and get-togethers, and we all have people who fall in and out of our lives. But everyone has two biological parents. OK, OK, some people might have more than two biological parents, but let’s keep it simple.

Going back a mere three generations, you have 8 direct biological great-grandparents, as this number doubles with each generation we go back.


Family Tree1

If we extend this to 6 generations (roughly 150 years for humans), our family tree increases even more dramatically to 64 direct ‘great-grandparents.’  

Family Tree2

And if we go back nine generations (about 225 years), we’re up to 512 direct ‘great-grandparents.’  

Family Tree5

I have to stop somewhere, since it’s tedious making these images. Essentially, the farther we go back in time, the larger our family trees (or is it pyramids?) become. And, the greater the chances that we share an ancestor. In the purely hypothetical example below, you and I may have an ancestor in common 9 generations ago. That’s obviously not the case for everyone reading this, but if we keep going back, our ancestry will inevitably meet somewhere down the road. 

Family Tree6

The reason for this is simple. If we do the math and keep doubling our ancestors every generation we go back, we very rapidly get into some enormous numbers, easily dwarfing the number of people who have ever lived. The only way that this can be true is if you and I — and everyone — share ancestors. This shared ancestry may not occur as recently as nine generations ago, but we’ll get there.

I think if we remember that while we all have our differences (biological, cultural, political, etc.), and we assign meaning to how our identities are not like everyone else’s, it can provide some perspective to remember that under the surface we connect somewhere. Further, those differences didn’t always exist, at least not in the same way they do in today’s world. Our differences matter, of course, but perhaps we can try to remember the similarities as well. After all, in a way, you’re family.



Scheper-Hughes, N., 2001. Saints, Scholars, and Schizophrenics: Mental Illness in Rural Ireland. Univ of California Press.

One thought on “Our Overlapping Family Trees

  1. Pingback: Human Family (We Are More Alike, My Friends, Than We Are Unalike) – Patrick F. Clarkin, Ph.D.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.