Scientists on Wednesday announced landmark discovery in Ethiopia of a nearly complete skull of an early human ancestor that lived 3.8 million years ago, and species boasting an intriguing mixture of apelike and humanlike characteristics.
The fossil dubbed MRD, which provides insights into a pivotal period for evolutionary lineage that eventually led to modern humans, belongs to the species Australopithecus anamensis, which first appeared roughly 4.2 million years ago.
These species are considered the direct ancestor of Australopithecus afarensis, the species best known from the famous partial skeleton nicknamed Lucy unearthed in 1
MRD and Lucy together stand as watershed fossils for illuminating early human ancestors.
“This is a once-in-a-lifetime discovery, and there was nothing mo re exciting than that, ”said Cleveland Museum of Natural History paleoanthropologist Yohannes Haile-Selassie, the leader of research published in the journal Nature. “We are talking about the most complete cranium of an early human ancestor ever found in the fossil record older than 3 million years.”
Until now, the only Australopithecus anamensis cranial remains isolated jaw fragments and teeth, making it difficult to fully understand the species. The skull is critical to learning about species' diet, brain size and facial appearance.
The discovery finally allows scientists to "put a face to the name" regarding Australopithecus anamensis, said paleoanthropologist and study co-author Stephanie Melillo of the Max Planck Institute for Evolutionary Anthropology in Germany.
"The anatomical features in this skull help us characterize these species, which turn our ideas about the evolutionary relationships among species," Melillo added.
MRD's species, which was bipedal but may also be able to move around in trees, was much smaller than modern humans.
Its skull, found about 340 miles (550 km) northeast of Ethiopia's capital Addis Ababa, measures about 8 inches (20 cm) wide and 4.5 inches (11.5 cm) wide. Previous research suggested the species reached about 5 feet (1.5 meters) tall, but the researchers did not give a height estimate for this individual, apparently an adult male.
'A PRIMITIVE FACE'
The upper jaw, sticking out of the ground, was the first piece found, leading to the recovery of the skull rest.
“What we see in the new cranium is like a primitive face,” Haile-Selassie said.
It had a robustly built and long face with protrusive jaws and a well-developed "sagittal crest," a ridge of bone atop the head indicating strong jaw muscles. The researchers said it apparently inhabited arid shrubland near a river delta and lake.
It hails from a time between 4.1 million and 3.6 million years ago when early human ancestor fossils were extremely scarce.
The evolutionary lineage that led to people split from the chimpanzee lineage roughly 6 million to 7 million years ago, gradually acquiring traits such as bipedal walking, flatter face and increased brain size through the success of species. Our species, Homo sapiens, appeared roughly 300,000 years ago in Africa.
In scientific parlance, MRD's species was hominin, a group containing modern humans, extinct human species and immediate ancestors including various Australopithecus species. MRD's skull shows a combination of primitive traits seen in older species as well as characteristics resembling those in later hominins.
In MRD, there are some primitive features similar to those in an earlier group called Sahelanthropus, including a long and narrow shape of
The MRD also shows a reduction in canine size from older species, although these teeth are still larger than Lucy's species, as canine size progressively diminished among later hominins.
Until now, the earliest Australopithecus anamensis fossils were 3.9 million years old. The MRD fossil age indicates these species co-existed for approximately 100,000 years with Lucy's species, challenging previous notions that earlier species had evolved into later ones with no overlap.
“The fact that these two very closely related species were overlapping both temporally and spatially bringing up new questions about whether they were competing for resources like food or space, ”Melillo said.
“ What we are seeing here is that our evolution was not completely constituted by a linear transformation by one species to another, ”Haile-Selassie added.
(This story has been published from a wire agency feed without modifications to the text. Only the headline has been changed.)
First Published :
Aug 29, 2019 07:59 IST