The 10,000-year-old bone and the first dogs in America

Scientists have sequenced the genes of the oldest known dog in the Americas. Its only remains are a 10,000-year-old scrap of bone, but by comparing its DNA to its closest Siberian relatives, they’ve been able to figure out roughly when its ancestors split and moved into the Americas - and interestingly, this date corresponds with when we think humans did the same.

This story actually began in the 90s, when geologist Timothy Heaton excavated an Alaskan cave, and uncovered piles of bone fragments. He brought them back to the University of South Dakota, and spent decades sifting through them, alongside a number of collaborators that include the University at Buffalo's Charlotte Lindqvist. Charlotte told Phil Sansom there was one, unassuming, little piece of skeleton that ended up being more that it seemed…

Charlotte - This particularly tiny bone here we weren't sure of. We knew it must have come from a mammal, and we thought it could be a bear because there were all these other bear bones in this cave. We got the DNA from it, and then we discovered this doesn't really look like bear DNA. And then comparing it to just a large database of DNA sequence data we could see that it matched best to dog or potentially wolf, because dogs and wolves are closely related. And that was not what we were expecting, I mean, from all the bones that we have analysed from these caves, we have never before come across a dog. And of course a dog is quite spectacular, because we know if there was a dog, there must have been humans.

Phil - Right, because dog is the version of wolf that we've domesticated, so if you find it's dog and not wolf, humans must have been around?

Charlotte - Exactly, yes.

Phil - How old was this dog?

Charlotte - It's actually the oldest bone in this cave. It's around 10,000 years old. Actually it is then among the oldest domesticated dogs from the New World that we have confirmed.

Phil - Is New World... is that the Americas?

Charlotte - Yes.

Phil - Wow, a 10,000 year old dog bone. It must have been in pretty bad condition after so long. How much of the DNA, then, did you end up piecing together?

Charlotte - What we focused on, and have focused on so far, is the mitochondrial DNA. But we were able to... the DNA was fairly well preserved, and we were able to put together an entire mitochondrial genome from this little bone.

Phil - Does that then tell you sort of where this dog came from - a bit about its family tree?

夏洛特-是的。所以当我们有这个mitochondrial genome sequence, we can compare that with dogs from the New World, modern dogs, and what we have available of other ancient dogs, of wolves, and including ancient dogs that have been found in the Americas. And we've found that our ancient 10,000 year old dog from Alaska was a close relative of these dogs. So it sort of suggested to us that it must be a descendant of a very early or extinct lineage. It came from Siberia, like humans did, moved along the coast and into the rest of the Americas south of the ice sheets.

Phil - You're saying that this dog might've been kind of the puppy, of the puppy, of the puppy, of the first dog in America?

Charlotte - Something like that!

Phil - Oh my god!

Charlotte - They probably diverged from these Siberian dogs more than 16,000 years ago.

Phil - You already talked about how they're really closely linked with humans. So do you know what humans they would have come with?

Charlotte - It's fairly clear... and we can see that too from the diet of this dog that it had a largely marine diet. And dogs are not very good marine mammal hunters or fishers, so it must have eaten food that humans gave it. So this dog must have been with humans, right. We also do have human artefacts and actually human remains from this area, even from around this time around 10,000 years ago. From genetic data as well we have estimates that these native indigenous people that moved into America split from their Siberian ancestors around the same time as the date that we find for these dogs. So it strongly suggests that the first people that moved into the Americas brought their dogs with them.

Phil - That's wild. The very first people?

Charlotte - The very first people and the very first dogs.

Phil - What should I be picturing? Were these people coming through Siberia and over into Alaska with chihuahuas, or what?

Charlotte - All these modern dog breeds that we know of today, everything from chihuahuas to great Danes, are really only a few hundred years old. I think you would probably more like imagine something like a malamute or a sled dog, something maybe looking a little more closer to a wolf.