Ancient DNA and the search for the dodo’s cousin

Ancient DNA can yield surprising answers to questions about the evolution and relationships between species.

Let’s get this out of the way: Ancient DNA is going to remind you of Jurassic Park. Recent headlines involving ancient DNA, or paleogenetics, involve reconstructing the DNA of the giant moa bird using its feathers, identifying the remains of a 4,000 year old mummy from its teeth, and sequencing the genome of a woolly mammoth from its hair. (Listen to our interview with Stephan Schuster for more on that mammoth.) Scientists’ quest to understand the building blocks of long-gone creatures could lead you down a slippery slope to visions of a potentially dangerous fun park out of moas, mammoths, and mummies (oh my!).

Sure, maybe one day we could impregnate an elephant with a woolly mammoth. But today, scientists are using ancient DNA to yield surprising answers to questions about the evolution and relationships between species. It was 25 years ago when scientists developed a technique for extracting DNA from mitochondria in old bones and other biological material, allowing us to get a glimpse of the genetic past.

Beth Shapiro is an evolutionary biologist who, at the age of 33, won a MacArthur Fellowship (also known as the “Genius Grant”) for her work using ancient DNA to trace the histories of extinct or threatened species. We spoke over the phone, and she told me that she’s interested in ancient DNA because as she says, “You can look into the past and see evolution as it’s happening.” Shapiro told me about her first foray into ancient DNA – looking for the modern-day relatives of the famously extinct dodo bird.

Beth Shapiro: Everyone knows what the dodo is – it’s a big flightless bird that’s extinct, probably because humans made it go extinct when they arrived on Mauritius [in the Indian Ocean] a couple hundred years ago. The question we wanted to ask was what kind of bird is the dodo? What’s the evolutionarily closest living bird to the dodo? To do this, we decided that we were going to extract a little bit of DNA from dodo remains, that we might have found either on Mauritius, or museums that were around Europe. And we tried, and we tried, and we failed.

But finally, we were able to get DNA from the only complete skeleton of a dodo that’s available. That’s at the Oxford University Museum of Natural History. We carved a little chunk of bone out of its leg. I think that’s one of the most frightening experiences of my time as an ancient DNA scientist so far – destroying this precious specimen. Well, not destroying it, but certainly making my mark.

So we carved a little bit of DNA out of its leg, and we were able to extract a small fragment of mitochondrial DNA. We found out that the dodo was most related to pigeons. It’s long been known that dodos were probably closely related to pigeons, but it was thought that they were in some kind of sister group. But in fact, the DNA tells us that the dodo falls within the diversity of pigeons in the world. So it’s just a big, flightless pigeon. And the most closely related pigeon to the dodo is a beautiful bird called the nicobar pigeon.

Shapiro is now focused on reconstructing the population dynamics of ancient species, using many samples of DNA to understand the history and behaviors of large animals many millennia into the past. She says that the next step for ancient DNA is to improve modern tools, in order to work with more degraded samples and get more information out of the DNA. She says eventually, the conclusions we can make from the past might tell us about surviving extinctions in the future – science that’s especially relevant as we lose species today.

To hear Beth Shapiro speak on how ancient animals fared in past climate, click here.

Lindsay Patterson