Scientists have long classified different species of hominids based on sometimes subtle variations as well as when and where they were found.
But the five Dmanisi skulls exhibit a range of characteristics ascribed to hominid species spanning a vast geography and time period, from 2.4 million year old African remains to finds from Asia and Europe that are half that age.
Scientists now have accurate methods (see below ) for dating fossils.
methods rely on characteristic faunal and geological patterns to bracket the period when the fossil existed.
A complete skull found in the Eurasian country of Georgia could be evidence that early hominids are actually all members of a single species.
The view challenges long-held ideas about human evolution and could upend decades of classifying early hominids into different species, such as today argue that the skull’s combination of primitive and more evolved features make it difficult to classify by currently accepted definitions of early hominid species.
Ernst Mayr reduced all the hominid (human ancestor: (see hominid books)) fossil records to three species, A.
Sahelanthropus may represent a common ancestor of humans and chimpanzees.
However, if Toumaï is a direct human ancestor, then its facial features bring the status of Australopithecus into doubt because its thickened brow ridges were reported to be similar to those of some later fossil hominids - such as Homo erectus - whereas this morphology differs from that observed in all australopithecines, most fossil hominids and extant humans.
The skull’s cranium and jaw bone were found five years apart, about six feet from each other, but researchers are confident they came from the same individual.
The skull has a mosaic of both primitive and more evolved features, such as a small braincase and long face, not previously seen together in the fossil record.