Is this new species a human relative?


Fossils found in an underground cave in South Africa may be from a previously unknown species of the human genus, Homo.

The fossils come from at least 15 individuals. They were pulled from a pit 30 meters (100 feet) deep. Lee Berger led the team of excavators. He works at the University of the Witwatersrand in Johannesburg, South Africa. His team reported details of its find September 10 in the journal eLife.

The skeletal remains display a mix of traits. They are unlike anything researchers had seen before. The bones and teeth have some features that are similar to humans. But the fossils also have some apelike qualities. The same traits are seen in 2-million- to 4-million-year-old fossils that belong to Australopithecus(Aw-STRAL-oh-PITH-eh-kus). It’s an extinct genus that is a close relative to the genus Homo.

As a paleoanthropologist, Berger studies fossils and cultural clues left behind by ancient humans and their relatives. The fossils his team has just recovered come from a new species. They’ve named it Homo naledi. The word naledi means star in South Africa’s Sotho language. “We don’t know how old these fossils are,” Berger said September 9 during a news conference. “But based on its anatomy, H. naledi clearly sits near or at the root of the Homo genus.” By anatomy, he means the shape and arrangement of body parts.

Remains of the new hominid were recovered in November 2013 and March 2014. That was shortly after two cave explorers discovered the fossils and alerted Berger. The fossils sat in a pit now nicknamed Dinaledi Chamber. But Berger and most researchers were too big to get to it. That’s because it sits at the end of a narrow hole 90 meters (300 feet) deep. So Berger’s team recruited six slender researchers who also were experienced cave explorers. They eventually found 1,550 H. naledi fossils on the cave floor and buried in the soil.

Berger’s team doesn’t yet know how old any of the bones are. The fossils lay in soft sediments that have partly mixed together over time. That means the researchers can’t know the bones’ original location. If they did know that, it could have helped the team determine their age. Nor were fossils of other animals found near the hominid remains. That deprived researchers of another clue to H. naledi’s age.

Without knowing how old the bones are, some researchers are skeptical about the find. Without those dates, it remains unknown how important the discovery is for understanding the human family tree, says Carol Ward. She, too, is a paleoanthropologist. She works at the University of Missouri in Columbia.

If the fossils date to more than 2 million years ago, though, H. naledi would become one of the oldest members of the human genus. A date younger than 2 million years would support the idea that manyHomo species once coexisted in Africa. They would have lived at the same time as many Australopithecusspecies.

Berger and his colleagues estimate that H. naledi stood an average of about 1.5 meters (5 feet) tall. Adults would have weighed around 45 kilograms (almost 100 pounds).

Nearly complete hands of Homo naledi display humanlike finger proportions. But the finger bones are curved, like those of ancient, tree-climbing hominids.

Many skull features link H. naledi to ancient Homospecies, the researchers say. So do small teeth and jaws. Long, relatively light leg bones and humanlike ankles and feet indicate H. naledi would have had a smooth, upright gait. The hominid’s wrists and hands also look much like those of early Homo species.

In contrast, H. naledi’s shoulder, rib cage, pelvis, upper leg and curved fingers should have enabled it to climb trees well, the investigators say. That is something seen in Australopithecus species. H. naledialso had an Australopithecus-sized brain. That means it was about the size of an orange.

Opinions about the finds vary among paleoanthropologists. For instance, “Despite the small brain, this new species is clearly part of the genus Homo because of the way the skull is built,” says Fred Spoor. He works at University College London. Still, he doubts H. naledi was a direct ancestor of modern humans.

Christoph Zollikofer agrees that the fossils probably belong in the Homo genus. But this University of Zurich scientist thinks the bones look “strikingly similar” to nearly 1.8-million-year-old Homo erectusfossils found in West Asia. So he wonders whether the South African hominids may have belonged to H. erectus. While living at the bottom of the continent, they might simply have evolved a few skeletal innovations, such as distinctive hands, he suggests.

7:00AM, SEPTEMBER 28, 2015
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Source: Fossils: Is this new species a human relative? | Science News for Students


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