Enlarge (credit: Italian Culture Ministry)

Archaeologists in Italy recently unearthed the remains of at least nine Neanderthals in Guattari Cave, near the Tyrrhenian Sea about 100 km southeast of Rome. While excavating a previously unexplored section of the cave, archaeologists from the Archaeological Superintendency of Latina and the University of Tor Vergata recently unearthed broken skulls, jawbones, teeth, and pieces of several other bones, which they say represent at least nine Neanderthals. That brings the cave’s total to at least 10; anthropologist Alberto Carlo Blanc found a Neanderthal skull in another chamber in 1939.

Italy was a very different place 60,000 years ago. Hyenas, along with other Pleistocene carnivores, stalked rhinoceroses, wild horses (an extinct wild bovine called aurochs), and people.

“Neanderthals were prey for these animals. Hyenas hunted them, especially the most vulnerable, like sick or elderly individuals,” Tor Vergata University archaeologist Mario Rolfo told The Guardian. The archaeologists found the Neanderthal remains mingled with the bones of rhinos, giant deer, wild horses, and other hyenas. Predators and scavengers tend to leave behind different parts of the skeleton than, say, flowing water or simple burial—and tooth marks are usually a dead giveaway.

Enlarge / A mammoth tusk thaws out of the ground in Siberia.

Ancient DNA has revolutionized how we understand human evolution, revealing how populations moved and interacted and introducing us to relatives like the Denisovans, a "ghost lineage" that we wouldn't realize existed if it weren't for discovering their DNA. But humans aren't the only ones who have left DNA behind in their bones, and the same analyses that worked for humans can work for any other group of species.

Today, the mammoths take their turn in the spotlight, helped by what appears to be the oldest DNA ever sequenced. DNA from three ancient molars, one likely to be over a million years old, has revealed that there is a ghost lineage of mammoths that interbred with distant relatives to produce the North American mammoth population.

Dating and the mammoth family tree

Mammoths share something with humans: like us, they started as an African population but spread across much of the planet. Having spread out much earlier, mammoth populations spent enough time separated from each other to form different species. After branching off from elephants, the mammoths first split into what are called southern and steppe species. Later still, adaptations to ice age climates produced the woolly mammoth and its close relative, the North American mammoth, called the Columbian mammoth. All of those species, however, are extinct, and the only living relatives are the elephants.

Enlarge / The puppy's remains are dried out but mostly intact thanks to being buried in permafrost. (credit: Government of Yukon )

This Ice Age wolf puppy doesn’t look much like a fearsome predator, what with her tiny puppy teeth and soft little ears. According to her DNA, however, the mummified puppy, named Zhùr, came from a population that's among the ancestors of all modern wolves. Canada’s permafrost freeze-dried her remains shortly after her death around 57,000 years ago.

“She’s the most complete wolf mummy that’s ever been found. She’s basically 100 percent intact—all that’s missing are her eyes,” said Des Moines University paleontologist Julie Meachen.

Puppy surprise

In July 2016, miner Neil Loveless of Favron Enterprises was searching for gold in Alaska’s famed Klondike gold fields. He was water-blasting the frozen mud along the banks of Last Chance Creek. It’s a process called “hydraulic thawing,” meant to thaw and soften the frozen permafrost so miners can search for gold in the streambed deposits, an approach called placer mining. But Loveless found something far stranger and even more interesting than Klondike gold: a frozen, mummified wolf puppy.

Comparison of Modern Human and Neanderthal skulls from the Cleveland Museum of Natural History. (credit: hairymuseummatt )

We know that Neanderthals left their mark behind in the DNA of many modern humans, but that exchange worked both ways. The groups of Neanderthals our species met in Eurasia around 45,000 years ago already carried some Homo sapiens genes as souvenirs of much earlier encounters. A recent study suggests that those early encounters allowed the Homo sapiens version of the Y chromosome to completely replace the original Neanderthal one sometime between 370,000 and 100,000 years ago.

Evolutionary geneticists Martin Petr, Janet Kelso, and their colleagues used a new method to sequence Y-chromosome DNA from two Denisovans and three Neanderthals from sites in France, Russia, and Spain (all three lived 38,000 to 53,000 years ago). The oldest Neanderthal genomes in Eurasia have Y chromosomes that look much more like those of Denisovans. Later Neanderthals, however, have Y chromosomes that look more like those of us humans.

Gene flow is a two-way street

Tens of thousands of years ago, our species shared the world with at least two other hominins. The tools, beads, and art they left behind hint that these other humans were probably a lot like us. And we were definitely all alike enough to have, apparently, a bit of sex.

Enlarge / Modern reconstruction of a Viking longboat. (credit: Dun.can / Flickr )

A recent study of ancient DNA sheds light on who the Viking groups were and how they interacted with the people they met. The Viking Age, from around 750 to 1100 CE, left a cultural and economic impact that stretched from the coast of North America to the Central Asian steppe, and archaeology shows several examples of cultural exchange spanning continents. But to see patterns in how people swapped not only ideas, but genes, we need to look at the DNA of ancient people.

“We know very well that the Viking Age changed the cultural and political map of Europe a thousand years ago, but we don't really know much about the demographic changes that accompanied these changes,” University of Copenhagen genomicist Ashot Margaryan told Ars. “This can be addressed based on population genetics methods.”

Who were the Vikings?

Today, we tend to think of the Vikings as one big mass of bearded raiders, swooping down European coasts, up rivers, and across the North Atlantic. But the Vikings themselves didn’t see themselves that way at all. The people who set sail to raid, trade, fish, and settle during the Viking Age saw themselves as members of distinct groups, with a shared culture but not a shared identity. The genetic evidence, it turns out, is on the Vikings’ side.