Homo erectus wasn’t the first human species to leave Africa 1.8 million years ago, fossils suggest
The earliest ancestral members of the human lineage may have left Africa earlier than generally thought, a new study of fossil teeth suggests.
Modern humans, Homo sapiensare the only living member of the human lineage, Homowhich appeared in Africa around 2 to 3 million years ago and first left this continent a a few hundred thousand years ago. But many others extinct human species previously roamed the Earth, like Homo habilisbelieved to be an early stone tool maker, and Homo erectusthe first to regularly preserve the tools she made.
The Dmanisi fossils have sparked intense debate due to the unusual level of variation they exhibit. Many researchers have suggested that these specimens all belong to H. erectusthe anatomical diversity observed between specimens resulting from factors such as natural differences between the sexes. Other scientists have argued that the Dmanisi fossils represent two distinct human species. One, nicknamed Georgian homoseemed more closely related to the predecessors of humans known as australopiths, while the other, Homo caucasianseemed more similar to early human species.
Resolving this controversy could reveal whether H. erectus was the first human species to leave Africa, or if others preceded it, study co-author Victor Néryhistorian and archaeologist at the University of São Paulo in Brazil, told Live Science.
Previous analyzes of the Dmanisi fossils have focused primarily on the skulls. In the new study, published December 3 in the journal PLOS Oneinstead, researchers focused on the similarities and differences between the teeth.
Scientists analyzed 24 teeth from three individuals in Dmanisi. They compared them not only with each other, but also with 559 teeth from other species, including australopiths, early humans such as H. habilis And H. erectusand modern humans.
The researchers found that the teeth appeared to fall into two groups, one closer to australopiths and the other more similar to early humans. The differences between these groups were particularly evident in the teeth of the upper jaw.
These dental findings suggest “that there was probably more than one species present in the Dmanisi region”, co-author of the study. Mark Hubbedirector and professor of anthropology at the University of Tennessee at Knoxville, told Live Science.
The scientists noted that the differences between these two groups of teeth were similar to the levels of differences observed between the sexes in chimpanzees and gorillas. This raises the possibility that they represent the teeth of both sexes in the same species. However, researchers argued that the Dmanisi fossils did not come from a single human species, since the group most similar to australopiths had relatively large third molars, in contrast to the tendency for humans to have smaller third molars compared to their parents.
“I agree with the authors that Dmanisi probably has more than one lineage represented,” Chris Stringera paleoanthropologist at the Natural History Museum in London who was not involved in this study, told Live Science. The big but little brain “the skull looks much more primitive than the others – at least [H.] habilis-like, otherwise Australopithecus. The others could still represent a very primitive form of [H.] erectuswhich has been the dominant opinion until now.
If one accepts the new study’s findings that two species were present in Dmanisi at the same time, then the larger implication is that “there was an older, more ‘primitive’ species that migrated out of Africa than is generally thought, which is quite interesting.” Karen Baaba paleoanthropologist at Midwestern University in Glendale, Arizona, who was not involved in this work, told Live Science.
If the human species had actually left Africa before H. erectusthese early humans “could have given rise to distant descendants like [H.] luzonensis, [H.] floresiensis And Meganthropist“, added Stringer. (Fossils of Meganthropistan extinct primate, were first discovered in Indonesia in the 1940s, and scientists have long wondered whether they were an ape, an australopith, or a member of an early human species.)
However, Baab cautioned that these new findings do not conclusively prove that there was more than one species in Dmanisi. For example, she noted that the new study’s analysis of lower jaw teeth suggested that these fossils might belong only to H. erectusand not two species.
Although the new study claims that the simplest explanation for its results is that multiple species existed at Dmanisi, the simplest explanation might actually be “to propose a single, albeit highly variable, species where some individuals retain more ancestral characteristics and others drift more toward later species.” Homo erectus” said Baab.
