Friday, November 14, 2014

Science, Mystery, and the Ultimate Family Tree

Over the last couple of decades, the general public's knowledge about the field of genetics has progressed to the point where most people have at least a vague understanding of what DNA is and that many scientists are interested in it. That said, the average person - myself included - probably doesn't understand a whole lot about the differences between terms like "gene" and "genome" or "chromosome" and "mitochondrial".

Last year, I was convinced to add a few of my cheek cells to the growing pool of DNA data being collected for the purposes of analysing heredity. Genealogists are an obvious target group for this service, since our primary goal is to prove relationships between small populations over time - and musty old documents can really only take you so far.

Being a novice in every sense of the word on this subject, I can't really speak to the details of how DNA analysis works. (I could try right now, but I would get those details very, very wrong.) What I do know is that  studying DNA can tell us quite a lot about the past. Comparing my sample to samples from thousands of other people can show me where my ancestors came from, and where to look for modern relatives. Right now, our ability to use this tool is still developing; after all, it has only been 61 years since Crick and Watson published their paper revealing the structure and nature of the molecule. But it is developing.

The discovery of DNA is for biology what the invention of the telescope was for astronomy. In the same way that looking at the stars and measuring the characteristics of their different wavelengths can allow us to observe the history of the universe for 13 billion years in every direction, the DNA of every organism on this planet also allows us to observe the distant past and learn about a much larger family tree than the one that even the most ambitious genealogist would dare to tackle.

I borrowed the following from something PZ Myers posted on Pharyngula:
"The image below is a phylogram, illustrating the degree of variation in a sequence of mitochondrial DNA. The concept is fairly simple: if two DNA samples are from individuals that are evolutionarily distant from one another, they’ll have accumulated more differences in their mitochondrial DNA, and will be drawn farther apart from one another. If the two individuals are closely related, their DNA will be more similar, and they’ll be drawn closer together. That’s the key thing you need to know to understand what’s going on."

Unrooted phylogram of mitochondrial DNA sequences.
Gagneux P1, Wills C, Gerloff U, Tautz D, Morin PA, Boesch C, Fruth B, Hohmann G, Ryder OA, Woodruff DS. (1999) Mitochondrial sequences show diverse evolutionary histories of African hominoids. Proc Natl Acad Sci USA 96(9):5077-82.

As he goes on to talk about the tiny clump of red branching off to the upper right of the image, he points out how the data demonstrates just how closely related all humans are to each other. This reinforces what we family historians have always known - if you can go back far enough, we're ALL related! And just as DNA analysis has begun to help us prove and disprove things that we thought we knew about our human relatives, it is also proving things about our past that were previously only guessed at.

It probably won't happen very often, because I'm slow and this science stuff is complicated, but I hope to continue learning from my DNA analysis, and if I can find some things that I understand well enough to share here, I certainly will!

To get in on the act yourself, there are a number of services offering DNA analysis for family history. The biggest is, naturally, but if you want to measure yourself against my sample, you'll need to check out - let me know if you do and if you suspect we might be cousins, so I know to look for you.

And that invitation is open even if you are a Sumatran Orangutan - the most distant cousin on the map!


  1. I know how controversial this is in some quarters, but in my experience, that controversy is driven by fundamental misunderstanding of what science claims to be able to prove. To learn more about what we know and how we know it, I highly recommend taking the time to watch PBS's presentation of "Your Inner Fish" hosted by Neil Shubin, and based on his book.

    The YouTube channel is online here:

    It really drives home the point that studying DNA does for biology what telescopes did for astronomy!