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Yohannes Haile-Selassie
Yohannes Haile-Selassie

Scientists Say They've Found a New Species of Human Ancestor

Yohannes Haile-Selassie
Yohannes Haile-Selassie

Lucy, our famous human ancestor who for decades held the title of the oldest most-complete ancient hominin ever found, may have had some surprising neighbors in Ethiopia more than 3.3 million years ago. New research contends that Lucy’s species, Australopithecus afarensis, wasn’t the only ancient human relative in the area.

Based on the discovery of teeth and jawbones from between 3.3 and 3.5 million years ago, Yohannes Haile-Selassie of Case Western Reserve University and the Cleveland Museum of Natural History and his fellow researchers describe a new hominin species called Australopithecus deyiremeda in a new paper in the journal Nature. (Hominins include humans and their extinct relatives.) The bones were found just 20 miles from where Lucy was discovered in Ethiopia in 1974. 

The researchers argue that the size and shape of the teeth found are different enough from previously discovered human ancestors—including A. afarensis and other proposed species like Kenyanthropus platyops (found in Kenya) and Australopithecus bahrelghazali (found in Chad)—to be classified as a new species. “There is now incontrovertible evidence to show that multiple hominins existed contemporaneously in eastern Africa during the Middle Pliocene,” they write. Only a few years ago, the same researchers found a hominin foot fossil that also suggested another species besides Lucy—one that would not have walked upright. 

Image Credit: Haile-Selassie et. al, Nature, 2015

However, the issue of how many species of hominins existed at this time is far from solved. As evolutionary anthropologist Fred Spoor writes in a Nature article accompanying the research, “the increasingly rich fossil record of the middle Pliocene provides plenty of opportunity for lively debate,” which is a polite way of saying that plenty of anthropologists will be ready to duke it out for the next few years over the coexistence of multiple hominin species during this era.

Whether or not different species of human ancestors (and just how many) were around in addition to Lucy’s A. afarensis has been debated since the 1980s, with some anthropologists arguing that the diversity between some of the fossils discovered is too great for them to be one species. However, it can be difficult to determine how many species may have existed, because the bones that have been discovered have been only fragments of skeletons. (Lucy's skeleton is only 40 percent complete.) It can be hard to figure out how a particular species may have walked, for instance, if scientists have not found hip and foot bones. 

“It doesn’t really make sense for these four fossils to be isolated there as the only record of this species, when there are hundreds of fossils from the same time period so nearby,” anthropologist John Hawks explained via email. “If Haile-Selassie is right, then our fossil collection should already include some of this species, and a lot of what others have written about the evolution of early hominins in this part of the world will fall apart.”

This finding "undeniably shows that there’s more diversity than we thought in the early branches of human evolution,” says Brian Richmond, curator of human origins in anthropology at the American Museum of Natural History. “Early human evolution is more complicated than we thought." 

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Mark Golitko
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Stones, Bones, and Wrecks
6000-Year-Old Skull Might Belong to World's Oldest Tsunami Victim
Scientists speak to residents in Aitape.
Scientists speak to residents in Aitape.
Mark Golitko

Tsunamis and other natural disasters have taken a deadly toll on human populations for millennia, and now we may have the oldest example of that truth yet. An international team of anthropologists and environmental researchers recently analyzed a cracked skull that belonged to a person who likely died in a tsunami some 6000 years ago. They detail their find in a new study published in PLOS One.

The partial skull in question, known as the Aitape skull, was found in Papua New Guinea in 1929 during a geological survey by an Australian scientist named Paul Hossfield. It has since been dated to the mid-Holocene epoch, or around 6000 years ago.

For the current study, the scientists returned to the site of the 1929 discovery to sample and analyze the sediment there to find out more about what might have killed the person millennia ago. They had only Hossfield's basic field descriptions to go on, but University of Notre Dame anthropologist Mark Golitko, one of the study’s authors, says that based on those descriptions, they think they were able to sample within 100 yards or so of the skull's original location.

The top of a brown cracked skull against a pink background
Arthur Durband

Based on the grain size, chemical signature, and marine microalgae found within the sediment samples, they were able to determine that around the time that the skull was buried, the area was inundated with water, probably from a tsunami. At that time, the site, located near the present-day town of Aitape, would have been just along the shoreline. Aitape was also the site of a devastating tsunami in 1998, and the Holocene sediments resembled the ones associated with that disaster.

It's possible that the skull was buried before the tsunami hit, and the grave was ripped apart by the waters and the rest of the bones scattered. However, during the powerful 1998 tsunami that killed more than 2100 people in Papua New Guinea, bodies buried in modern cemeteries were not uprooted even as the sediment above them washed away, making it more likely that the ancient skull belonged to someone killed in the disaster.

The new analysis has "made us realize that human populations in this area have been affected by these massive inundations for thousands of years," study co-author James Goff of the University of New South Wales said in a press statement. "Given the evidence we have in hand, we are more convinced than before that this person was either violently killed by a tsunami, or had their grave ripped open by one."

Field Museum anthropologist John Terrell, another co-author of the study, said, "If we are right about how this person had died thousands of years ago, we have dramatic proof that living by the sea isn't always a life of beautiful golden sunsets and great surfing conditions."

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science
6 Pioneering Facts About Mary Leakey

Fossil bones and the earliest footprints of our human ancestors are just a few of Mary Leakey’s groundbreaking discoveries. Get to know the legendary paleoanthropologist, and learn how her serendipitous finds forever altered scientists’ understanding of human origins.

1. MARY LEAKEY WAS A BORN EXPLORER.

Mary Leakey (1913-1996), née Mary Nicol, was destined to be an explorer: Her father, Erskine Nicol, was a landscape painter, and the family traveled extensively through France, Italy, and Switzerland. While staying in a commune in southern France, 12-year-old Mary became interested in archaeology after meeting Elie Peyrony, a French prehistorian excavating a cave. Mary dug through his tiny finds—which included fine points, scrapers, and flint blades—and sorted them into an amateur classification system.

2. FOSSIL HUNTING WAS IN HER BLOOD ...

Leakey’s parents were artists, but hunting for fossils was part of her heritage: Her maternal great-great-grandfather was John Frere, an 18th-century English government official and antiquarian who’s credited with first recognizing Stone Age flint objects as early weapons and tools.

3. ... BUT SHE WASN'T A GREAT STUDENT.

Leakey was intelligent, but she also had a rebellious streak. As a teen, she was expelled from several Roman Catholic convent schools—once for intentionally creating an explosion in a chemistry lab. Figuring she wasn’t cut out for a classroom, Leakey never finished high school, and decided to pursue independent studies in art, geology, and archaeology at the University of London instead. (“I had never passed a single school exam, and clearly never would,” the scientist later wrote in her 1986 autobiography Disclosing the Past.)

4. LEAKEY WAS AN ARTIST WHEN SHE MET HER FUTURE HUSBAND AND RESEARCH PARTNER, LOUIS LEAKEY.

Mary Leakey—who inherited her father’s artistic skills— ended up working as an illustrator for archaeological digs. An archaeologist introduced her to Cambridge University paleontologist Louis Leakey, who needed an illustrator for his book Adam’s Ancestors (1934). The two became lovers, but their union resulted in scandal, as Leakey was still married at the time. The couple married in 1936, after Leakey divorced his first wife.

5. MARY LEAKEY'S FIRST BIG DISCOVERY WAS PROCONSUL AFRICANUS.

Mary Leakey's first major discovery came in 1948 when she found a fossil skull fragment of Proconsul africanus, an ancestor of apes and humans, which later diverged into two separate species. The fossil was thought to be more than 18 million years old.

6. ANOTHER ONE OF MARY LEAKEY'S FAMOUS FINDS CAME COURTESY OF ELEPHANT POOP.

In 1978, Leakey was on an expedition in Laetoli, in Tanzania, when members of her camp engaged in a spirited elephant dung fight. A scientist fell down, and he noticed strange indentations on the ground that had been recently exposed by erosion. They turned out to be tracks made around 3.7 million years prior, from animals that had walked over damp volcanic ash. Examining these prints took several years, but the team's efforts paid off when Leakey noted that one of the prints seemed to be made by a hominin. This discovery showed that early humans began walking upright long before scientists thought they had.

Additional source: Ancestral Passions: The Leakey Family and the Quest for Humankind's Beginnings, Virginia Morell

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