Now try putting those documents back together.
That’s the analogy that Bill Hart, chairman of the Miami University geology department, uses to describe the challenge faced by the hundreds of scientists who worked on the 17-year project to uncover a 4.4-million-year-old female partial skeleton nicknamed “Ardi,” whose discovery was announced last week in the journal Science.
Hart and Brian Currie, associate professor of geology, are among the 47 researchers who worked together to write the 11 scientific papers that comprise the special issue of Science detailing the project’s results.
Their part was to examine material surrounding the skeleton — rather than the skeleton itself — to determine what kind of environment Ardi lived in, and perhaps to speculate about her lifestyle.
The project will be detailed in a Discovery Channel special “Discovering Ardi: Changing Our Understanding of Human Origins,” airing at 9 p.m. Sunday, Oct. 11.
“While Brian and I won’t be among the talking heads you’ll see on that special, I was there for some of the filming,” Hart said. “So you might see my feet or rear end.”
Miami scientists help find human ancestor
Today, Ethiopia’s Afar Rift is a dry, barren place, similar to America’s Badlands, inaccessible to only the most intrepid scientific researchers willing to make the two-day trek from Addis Ababa, the nearest city some 140 miles away.
But 4.4 million years ago, it was a relatively lush forest and the home of hominid Ardipithecus ramidus, which thanks to an international team of scientists including Bill Hart and Brian Currie of the Miami University geology department, is now the oldest-known human ancestor.
The discovery includes the skull with teeth, arms, hands, pelvis, legs and feet of a female nicknamed “Ardi,” and pieces of 35 other hominid skeletons.
Hart and Currie are co-authors of “The Geological, Isotopic, Botanical, Invertebrate and Lower Vertebrate Surroundings of Ardipithecus ramidus,” one of the 11 papers by 47 scientists from 10 countries that comprise the special issue of Science detailing the results of a 17-year exploration of the area.
Laboratory research conducted at Miami was instrumental in producing a detailed chemical profile of the major constituents of the glass shards found in volcanic ashes sandwiching the fossils.
This unique chemical “fingerprint” allowed the Ardipithecus-bearing layer, which varies from 3 to 6 meters thick, to be tracked across a 9-kilometer arc of exposure, providing an unparalleled view of an ancient landscape.
“If you look at that layer, you’ll see all sorts of organic material, fossilized seeds and micro-fossils that point to a dense forest setting, a lot wetter than what you see there today,” Currie said. “There was some undergrowth, but mostly trees.”
The fossil evidence shows that Ardi shared her world with a variety of plants and animals that included fig and hackberry trees, land snails, parrots and peafowl, small mammals resembling shrews, mice and bats, two kinds of monkeys and several kinds of antelopes.
The results are historic because Ardi lived around 1.2 million years before Lucy, also found in Ethiopia, who until last week was the oldest-known human ancestor.
The new fossils reveal the early evolutionary steps that our ancestors took after we diverged from our common ancestor with chimpanzees, Hart said.
“The most important thing is that Ardi was an upright walker,” Hart said, “which challenges the long-held notion that our common ancestors with modern apes were more chimp-like.”
Ardi, he said, had feet with large digits resembling thumbs, which would have made running difficult, but well-adapted for climbing trees. Ardi’s hands indicate that she also may have walked on all fours, but palms down whereas modern day chimps walk on their knuckles.
Ardi lived only a few million years after the human line diverged from the line leading to modern-day chimpanzees and provides new insights on how modern hominids might have emerged from a common ancestral ape, but that long-sought after “missing link” remains a mystery, though Hart and Currie suspect the answer may well be in the Afar Rift.
“Finds like this will stimulate more research and give people more of an idea what to look for,” Currie said. “I’m sure some older fossils will be discovered and the gaps filled in further.”
In previous research projects, Hart was part of the team that identified the remains of the first Homo sapiens (published in Nature, 2003), and he and Currie were among scientists who recovered and identified fossils of the earliest species of the genus Australopithicus anamensis (published in Nature, 2006).
Contact this reporter at (513) 820-2188 or rjones@coxohio.com.
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