Thirteen hominin teeth have been discovered in Ethiopia in layers of volcanic ash between 2.6 and 2.8 million years old. The researchers think some of the teeth belong to one of the earliest members of the Homo genus, while others appear to be from a new hominin, suggesting both species lived alongside each other.
鈥淭hey either shared resources, and everything was hunky-dory, or maybe one of them was marginalised,鈥� says at Arizona State University. 鈥淲e just don鈥檛 know at this point.鈥�
Previous discoveries show that before around 3 million years ago, several species of early hominins in the genus Australopithecus lived in this region, including Australopithecus afarensis, the species to which the famous Lucy fossil belonged.
Advertisement
From around 2.5 million years ago, the first hominins from the genus Homo start appearing, with features more similar to those of modern humans. So what happened in between? To find out, Reed and her colleagues have been digging in an area called Ledi-Geraru, where there are volcanic deposits from this crucial time.
In 2013, her team found a 2.8-million-year-old jaw that appears to be from a Homo species, pushing back the origin of this genus. Now her team has found 13 teeth in three different layers of ash.
The teeth in the oldest and the youngest layers 鈥� which are dated to 2.79 and 2.59 million years ago 鈥� also belong to the genus Homo, according to the team. But they think the teeth in the middle layer 鈥� which is dated to 2.63 million years 鈥� are from an Australopithecus. The sites are all within a kilometre of each other.
鈥淲e were expecting to find more of our genus Homo, and then we found Australopithecus as well,鈥� says Reed.
What鈥檚 more, the Australopithecus teeth are different enough from those of A. afarensis and other australopithecines that the team thinks it is probably a new species. If they are right, it means the evolutionary tree leading to modern humans is bushier and more complex than we thought.
It is a great discovery, says at the University of Wisconsin鈥揗adison, but it is hard to draw conclusions based on a few teeth.
鈥淲hen you find evidence that spans 200,000 years, as these teeth do, you can鈥檛 be sure that they lived at the same time,鈥� says Hawks. 鈥淭hat鈥檚 a huge amount of time.鈥�
The identification of the teeth as separate species is also questionable. 鈥淢any fossils that we find combine features that are sometimes found in different species. You can always take a small sample and break it up into the most Homo-like and most Australopithecus-like,鈥� says Hawks.
鈥淭he question is what, statistically, you can say, and in this case the statistics on size measurements don鈥檛 show that the teeth are very different from each other. They鈥檙e in the range of overlap of early Australopithecus species and early Homo 蝉辫别肠颈别蝉.鈥�
Nature
Neanderthals, ancient humans and cave art: France
Embark on a captivating journey through time as you explore key Neanderthal and Upper Palaeolithic sites of southern France, from Bordeaux to Montpellier, with 快猫短视频鈥檚 Kate Douglas.
