Scientists Used Modern DNA to Reconstruct Part of a 19th-Century Man’s Genome

Have you ever wondered about one of your relatives from long ago? Maybe he was famous or you want to know where your family’s blue eyes came from or you’re just plain curious.

Until recently, you pretty much had to rely on family stories that were passed down through the generations to learn about your ancestors. But that is now set to change. With a little luck, a whole lot of science and genealogy, you may be able to use passed down DNA instead of stories to learn a bit about that great-great-great-grandfather.

This is exactly what the good folks at the San Francisco-based company AncestryDNA just did with David Speegle, a man born sometime around 1806. They were able to use the DNA of Speegle’s living descendants to piece together around 12% of the length of his genome. From this work, they were able to figure out that either he or one of his two wives probably had blue eyes and had the genes for early baldness.

This is just a start. As we learn more about human DNA, we will be able to learn a whole lot more about this long dead man from his recreated genome.

And now that AncestryDNA has worked out how to do this, they may be able to apply it to other deceased individuals as well. We may soon have a whole new way to learn about our past.

A Little Bit of Luck

Most everyone knows that they get half their DNA from their mom and half from their dad. What they might not have thought about is what happens to their DNA if they have just one child. Basically, at its simplest, half their DNA is lost forever!

Now of course it isn’t as simple as that. If you have brothers or sisters, they share right around half of their DNA with you and so their kids will share some of your DNA too. And if your parents had brothers and sisters they will share some of your DNA too. And so on.

Still, it becomes very tricky to track down DNA from people with few descendants. Which is why David Speegle made such an ideal test case.

He had 26(!) kids with two different wives and over 150 grandkids. His full set of DNA was pretty much passed on to the next generation multiple times.

This is where the luck comes in. For now, if you wanted something similar done for one of your relatives, you’d need to focus on someone that had lots of kids. That long-lost relative with two kids and four grandkids will probably remain a mystery for the foreseeable future.

So the first step is picking a relative with lots of kids and grandkids. But this is by no means the whole story. You also need to know the DNA of lots of your relatives and have lots of accurate, overlapping family trees.

A Lot of Science and Genealogy

David Speegle, his kids and his grandkids have all been dead for a very long time. What this means is that anyone alive today has, at most, tiny splinters of his DNA in theirs. These wisps of DNA need to be recognized and then combined to recreate David Speegle’s DNA.

Remember, you can’t compare the DNA of a relative with David’s DNA. His DNA is not available.

So, basically you are looking at as many of the people as you can at the bottom level of an enormous family tree that starts with David and his two wives. Fortunately, AncestryDNA has a good number of David Speegle’s descendants in the over 500,000 genomes in their database.

The researchers at AncestryDNA compared the DNA of all of the pairs of people for whom Speegle was the most recent common ancestor, one pair at a time, and looked for common DNA. They found a whole lot of it.

The next step was to find the DNA that is actually David’s and not some other shared relative’s DNA. This is trickier than it sounds because DNA doesn’t get passed down in predictable chunks from generation to generation. It gets all mixed, matched, and diluted in each generation.

This is where those family trees come in handy. You can subtract out DNA that is shared because of other relatives.

In fact, this is where the David’s two wives really helped. They made it easier to separate out the DNA that came from these two women compared to the DNA that came from David.

Not Just a Parlor Trick

Recreating David’s genome is more than just some heroic academic exercise. It also points to what we can learn about ourselves from testing the DNA of many relatives.

For example, people are using their DNA to trace their family’s ancestry. In fact, whole companies (including AncestryDNA) are based on just that premise.

Unfortunately, you can lose a lot of information if you test only yourself. Remember, you have only half of your mom and dad’s DNA. What this means is that you may miss more distant ancestry information.

Imagine that you had an Asian ancestor 5 or 6 generations back. This might mean that your parent has less than 5% of that Asian ancestor’s DNA in his or her DNA. If you happened to not inherit that part of your parent’s DNA, then the history of your Asian ancestry would be lost. (Click here for more information on these scenarios.)

One way to recover that information would be through something similar to what was done here for David Speegle. By comparing the DNA of lots of relatives you might be able to piece together that lost Asian history and learn a bit about yourself or confirm a family story.