Varied diet of early hominid casts doubt on extinction theory, says Colorado U studyNovember 10, 2006
The new study shows that Paranthropus robustus, once thought to be a "chewing machine" specializing in tough, low-quality vegetation, instead had a diverse diet ranging from fruits and nuts to sedges, grasses, seeds and perhaps even animals, said CU-Boulder anthropology Assistant Professor Matt Sponheimer. The findings cast doubt on the idea that its extinction more than 1 million years ago was linked to its diet, he said.
Paranthropus was part of a line of close human relatives known as australopithecines that includes the famous Ethiopian fossil Lucy that lived over 3 million years ago. Lucy is regarded by many anthropologists as the matriarch of modern humans.
"One line of Lucy's children ultimately led to modern humans while the other was an evolutionary dead end," he said. "Since we have now shown Paranthropus was flexible in its eating habits over both short and long intervals, we probably need to look to other biological, cultural or social differences to explain its ultimate fate."
A paper on the subject appears in the Nov. 10 issue of Science. Co-authors include the University of Utah's Benjamin Passey and Thure Cerling, Texas A&M University's Darryl de Ruiter, Ohio State University's Debbie Guatelli-Steinberg and Julia Lee-Thorp of the University of Bradford in Bradford, England.
Roughly 2.5 million years ago, the australopithecines are thought to have split into the genus Homo - which produced modern Homo sapiens - and the genus Paranthropus, Sponheimer said. Paranthropus stood about four feet tall and probably weighed less than 100 pounds, and its pelvis and leg structure indicate it was bipedal. Although the brain to body-size ratio in Paranthropus robustus is slightly larger than that of chimpanzees, "Paranthropus was not a mental giant," Sponheimer said.
The researchers used a technique called laser ablation to examine teeth from four individuals collected from the Swartkrans site in South Africa which contain isotopes of carbon absorbed from food during each hominid's lifetime. Since trees, shrubs and bushes produce a different carbon isotope signal than grasses and sedges, the team was able to determine that Paranthropus was often dramatically altering its diet over periods ranging from months to years.
"This is the first study to paint a portrait of an early hominid eating its way across a varied landscape," Sponheimer said. "None of us involved in the study dreamed Paranthropus would have had such a variable diet over thousands of years, much less in just a few months time."
Sponheimer speculated some Paranthropus individuals were moving back and forth between forested areas rich in fruits to a savanna and grassland landscape, perhaps along sedge-rich waterways. Since there also is evidence of year-to-year diet variation in the teeth, the team speculated the movements of Paranthropus may have been based to some degree on rainfall-related food variability, including the onset of droughts which can cause individuals to consume foods not normally preferred.
"We've never before been able to see dietary change within a single individual's lifetime," Sponheimer said. "It's like having a motion picture running over months and years instead of just having one still image."
Swartkrans is a renowned early hominid cave site containing remains of both Paranthropus robustus and early members of the genus Homo, he said. The cave is of high interest to archaeologists because it contains both bone and stone tools used by early hominids - including bone digging sticks thought to have been used to obtain termites or tubers - as well as one of the earliest known records of fire. The site contains animal bones burned at temperatures consistent with controlled fires.
While anthropologists are confident that the varied diet of early homo species - including meats and a wide variety of plant species - helped to propel the line into a successful run on Earth that continues today, the notion that an overly specialized diet doomed Paranthropus to extinction in a changing environment is now in doubt, he said.
So what ultimately led to the end of the line for Paranthropus? It could well have been direct competition with Homo - which was becoming skilled in extensive bone and stone technology - or it could have been a variety of other issues, including a slower reproductive rate for Paranthropus than for Homo, he said.
"One thing I do believe is that we need to seriously re-think the reason behind the ultimate fate of Paranthropus," said Sponheimer. "This 'who done it' or 'what done it' mystery is not likely to be resolved any time soon."
University of Colorado at Boulder
Related Early Hominid Current Events and Early Hominid News Articles
MU Expert Analyzes Fossil of Great Ape
Researchers who unearthed the fossil specimen of an ape skeleton in Spain in 2002 assigned it a new genus and species, Pierolapithecus catalaunicus.
Human, artificial intelligence join forces to pinpoint fossil locations
In 1991, a team led by Washington University in St. Louis paleoanthropologist Glenn Conroy, PhD, discovered the fossils of the first - and still the only - known pre-human ape ever found south of the equator in Africa after only 30 minutes of searching a limestone cave in Namibia.
'Nutcracker Man' Had Fundamentally Different Diet
An ancient, bipedal hominid needs a new nickname. Paranthropus boisei, a 2.3 million to 1.2 million-year-old primate, whom researchers say is an early human cousin, probably didn't crack nuts at all as his common handle suggests.
Ancient bipedal hominid dubbed 'Nutcracker Man' preferred grass to nuts, new study finds
An ancient, bipedal hominid sporting a set of powerful jaws and huge molars that earned it the nickname "Nutcracker Man" likely didn't crack nuts at all, preferring instead to slurp up vast quantities of grasses and sedges, says a new study.
Animal bone markings show evidence that 'Lucy' species used stone tools, ate meat
Two Arizona State University researchers conducting zooarchaeological and archaeometric analyses of four fossilized animal bone fragments found by the Dikika Research Project in northeastern Ethiopia - within walking distance of the discovery of the hominin skeleton "Lucy" (Australopithecus afarensis) - confirm that unusual marks on the bones were inflicted by stone tools.
First studies of fossil of new human ancestor take place at the European Synchrotron
Palaeoanthropologist Prof. Lee Berger of the University of the Witwatersrand, Johannesburg, South Africa, has discovered a new species of early human ancestor in one of the best-preserved skeletons of an early hominid, dated around 1.9 million years old, in the Cradle of Humankind, a World Heritage Site.
International team discovers new species of hominid
An international team of scientists has described a new fossil find and a new species of hominid, Australopithecus sediba, thought to be at least 2 million years old in an area of South Africa known as the Cradle of Humankind.
Microcephaly genes associated with human brain size
A group of Norwegian and American researchers have shown that common variations in genes associated with microcephaly - a neuro-developmental disorder in which brain size is dramatically reduced - may explain differences in brain size in healthy individuals as well as in patients with neurological and psychiatric disorders.
Early hominid first walked on two legs in the woods
Among the many surprises associated with the discovery of the oldest known, nearly complete skeleton of a hominid is the finding that this species took its first steps toward bipedalism not on the open, grassy savanna, as generations of scientists - going back to Charles Darwin - hypothesized, but in a wooded landscape.
'Peking Man' older than thought; somehow adapted to cold
A new dating method has found that "Peking Man" is around 200,000 years older than previously thought, suggesting he somehow adapted to the cold of a mild glacial period.
More Early Hominid Current Events and Early Hominid News Articles