Two well-preserved teeth recovered from sediments in Germany offer intriguing clues to how some of our distant primate relatives eked out a living in what is now northern Europe. But do these teeth, as many news outlets have proclaimed, “rewrite human history?” In a word, no.
The much-ballyhooed discovery comes in the form of two caramel-colored fossil teeth—one identified as a canine, the other as an upper molar—belonging to a primate that lived between nine and 10 million years ago. (Find out more about human evolution.)
Scientists dug up the teeth in September 2016 from Eppelsheim, a prehistoric site near Frankfurt that is famous for its primate fossils. A fossilized femur found at Eppelsheim in the 1820s helped kick start the fields of paleontology and paleoanthropology. Unfortunately, many of these fossils were lost during World War II, and few fresh samples have been found since. (See fossil teeth from the oldest modern human found outside of Africa.)
The two teeth described this week are the first new fossils of their kind to come out of Eppelsheim in 80 years, according to the researchers who examined them.
Study leader Herbert Lutz, the deputy museum director at the Mainz Natural History Museum, says that he and his colleagues have been dumbfounded by the teeth for the last year. Their paper, posted online Friday on the article-sharing platform ResearchGate, claims that the teeth bear a close resemblance to some extinct African relatives of modern humans.
In particular, they find that the oddly squat canine tooth closely resembles those of the extinct human relatives Ardipithecus ramidus and Australopithecus afarensis, the species best known from the fossil called “Lucy.” (Did a fall from a tree kill Lucy, one of our most famous ancient relatives?)
Lutz claims that the teeth are unlike anything found in Europe and Asia, but he's cautious about saying what that actually means.
“We want to hold back on speculation. What these finds definitely show us is that the holes in our knowledge and in the fossil record are much bigger than previously thought,” Lutz said in an interview with ResearchGate. “It’s a complete mystery where this individual came from, and why nobody’s ever found a tooth like this somewhere before.”
Perhaps the Eurasian primate bearing these teeth and its distant African relatives faced similar evolutionary pressures despite their geographic separation. This could have independently led them to similar tooth shapes, a widespread phenomenon in evolution called convergence.
Much Ado About Nothing?
Based on what Lutz's team has published, however, outside experts say that the teeth hardly “force us to reexamine the theory that humans originated from Africa,” as ResearchGate’s interview with Lutz attests.
For one, we must be careful not to confuse modern humans with hominins, the bigger lineage containing humans and our closest extinct relatives, or hominoids, the even bigger group containing hominins, chimpanzees, gorillas, and other apes.
Overwhelming fossil and genetic evidence points to an African origin for modern humans, who left Africa no earlier than 120,000 years ago and most likely between 50,000 and 80,000 years ago. The Eppelsheim teeth are roughly a hundred times older. If the Eppelsheim teeth say anything about human evolution, they help to clarify where and how the earliest hominoids lived and evolved.
But some experts in the field question if the teeth really belong to a hominoid.
The canine tooth described in the paper has an unusual, intriguing shape, says University of Toronto paleoanthropologist Bence Viola, an expert on the teeth of humans' extinct relatives. However, the molar—which he says is the more important tooth for classification purposes—contradicts any case for a human connection.
“I think this is much ado about nothing,” he says by email. “The second tooth (the molar), which they say clearly comes from the same individual, is absolutely not a hominin, [and] I would say also not a hominoid.”
Instead, most experts we contacted say that the molar probably belongs to a species of pliopithecoid, an extinct, primitive branch of primates that lived in Europe and Asia between roughly seven and 17 million years ago.
Pliopithecoids are very distant relatives of humans. Some paleontologists argue that this group diverged from the common ancestors of Old World monkeys and apes before those two branches even split from one another. In other words, it's likely that modern humans are more closely related to baboons than to the species represented by these teeth.
And as Lutz's team acknowledges in its paper, the molar closely resembles those of Anapithecus, a species of pliopithecoid known from a jawbone dug up in Hungary, says University of Toronto paleoanthropologist David Begun.
“The molar is important, because it validates an idea proposed by several researchers that a femur known from Eppelsheim since the 1820s actually does most likely belong to a pliopithecoid and not a hominoid,” says Begun.
Sergio Almécija, an anthropologist at George Washington University who also studies pliopithecoids, agrees. As for the supposedly hominin-like canine, the experts’ opinions range from interest to dismissal. Begun even doubts that it's a canine.
“The 'canine' looks to me like a piece of a ruminant tooth,” Begun says by email. Ruminants are cud-chewing, plant-eating mammals such as cows and sheep. “It has a funny break that makes it look a bit like a canine, but it is definitely not a canine, nor is it [from] a primate.”
Lutz cautions that he and his colleagues are only just beginning their analysis, which he says will include high-resolution x-rays and analyses of the teeth's wear patterns, which could help scientists reconstruct the primate's diet.
“Hopefully, in one or two years, we'll know a lot more about what we've got on our hands,” Lutz told ResearchGate. “It's definitely a fantastic, exciting story.”