In a cave called the "pits of bones" up in the Atapuerca mountains in Spain, the 430,000-year-old teeth collection is unusually smaller than could be expected for skulls in which they were found. In an anomaly, one scientist suggested that the lines of modern humans and neanderthals were divided some 800,000 years ago, tens of thousands of years earlier than the genetic studies predicted.
Aida Gomez-Robles, anthropologist at University College in London, studies how the teeth of ancient hominine species have evolved over the centuries. He believes that ancient teeth are too modern to their ears, but they have developed unusually fast, or, more likely, they have had more time for evolution than they generally believe. A new survey was published today in Zagreb Scientific progress.
As different types of hominine evolved, their teeth changed in significant ways, generally becoming smaller over time. Studying the teeth of various early human ancestors is one of the most common ways of distinguishing species and even identifying new ones. Previous studies by Gomeza-Robles show that teeth usually develop at a relatively standard rate in hominine history. If that's true, the thoracic and premolars dug out of the Spanish cave are smaller than they would have expected in view of their age.
"When we look at these teeth, they are very similar to the neanderthal teeth, though older," says Gómez-Robles. "In this study, we have been trying to examine how long this early Neanderthal need to develop this dental form, [which] it is similar to the dental form of Neanderthals much later.
Neanderthals i Homo sapiens to share a common ancestor, but exactly who this was, and when later the grapes separated from it, it is difficult to disclose. But there are traces, and the new study on teeth is far from the first evidence that even emerged from Sima de los Huesos, a fossil cave site in the Atapuerca mountains in Spain. The hominids who lived here, about 30 people who have been well studied over the years, by morphology and DNA, look like early Neanderthals – in fact, the remains are some of the oldest known Neanderthals. But how far were they actually close to the common one and the other missing species and our own?
Genetics has helped us to look into the past and sketch the ancient branches of the hominine family tree. Study of Neanderthal Remnants from Sima de los Huesos in 2016 estimates the time of Neanderthal separating from Homo sapiens genus from 550,000 to 765,000 years ago. Other genetic studies similarly suggest divergence times that were less than 800,000 years ago.
Paleoanthropologist Rick Potts, director of Smithsonian's Human Rights Program, says that although Gómez-Robles raises some persuasive ideas, he is far from convinced that the tooth evolution rates are standard or predictable as suggests work. "She has bitten an interesting subject here, but I just do not see the argument that the tooth evolution rates are absolutely known to the extent that we can say that Neanderthals-contemporary human divergence had to be 800,000 years ago," Potts said. "A lot of molecular-genetic studies suggest it's newer."
It is possible, says Gómez-Robles, that the teeth developed at an unusually high speed because of a strong selection for genetic changes. This accelerated change could occur if the remote population lived isolated from other neanderthals in Europe. However, Gómez-Robles believes that the teeth are easy to develop over a long period of time, which would, according to its time-frame, evolutionary changes to the teeth, divide between Homo sapiens and neanderthal genus 800,000 years or older before.
– Everything else, like a face [and] the anatomy of these hominines seems somewhat mediocre, "says Gómez-Robles. "It looks like we expected from the hominine that age, but the teeth look very, very different, they look very Neanderthal, and only the teeth are different … If there is a choice, we would expect it to affect something else, like a face and not just on the teeth. "
Potts also points to several possible causes of misinterpretation, including a variable called "generation time" that could greatly affect the evolution of tooth evolution over many thousands of years. "If you have faster or slower tooth development, growth, this would affect the assessment of the rate of evolution," he says.
Scientists have evidence that tooth development has changed during evolutionary times. Microscopic studies of tooth enamel layers allow researchers to calculate days between the birth of fossil hominine and the eruption of the first molar, showing that 1.5 million years ago, young people Homo erectus it has received its first spin about 4.5 years. About 200,000 years ago, Neanderthals had the same tooth for about 6 years, as we do today. "And we do not know when that 1.5 million years ago and 200,000 years ago, that rate changed to a much slower degree of tooth development," says Potts. "So that's a lot of room for bargaining."
Hybridization between different species, which appears to have spread throughout the ages, is still a possible complication. (The match between the modern human and neanderthal species occurred only 50,000 years ago.) "In this interglacial Europe, in this period of time, hell is broken, where the populations are separated from each other at certain times, are likely to evolve rapidly, returning to the thousands up to tens of thousands of years later, "says Potts. "We do not know what the effect of this evolutionary population history, which is always shared and returned, during the ice age and interglacial Europe, has had on the mechanisms of tooth evolution."
Considering the difficulty of spreading the various lines of ancient evidence and the relatively small difference between the genetic and evolutionary estimates of modern human-neanderthal divisions, one may wonder why finding the right time line is so important. But filling such gaps is the only thing we can accurately chart many evolutionary shoots and branches of our family tree – and learn how we became what we are.
"Even when the difference is not great," Gómez-Robles says, "the implications of these differences can be very important in terms of understanding the relationship between the different species and which are far from each other."
Do you like this article?
Sign up for our newsletter