Hand Fossil Turns Back Clock on Complex Tool Use
University of Missouri
Researchers have discovered a 1.42-million-year-old hand fossil that possesses the styloid process, a vital anatomical feature that allows the hand to lock into the wrist bones, giving humans the ability to make and use complex tools.
May 6, 2011 --
Neanderthals shared Europe with a mysterious member of our genus that may represent an entirely new species of human, suggests a paper accepted for publication in the Journal of Human Evolution. The study describes the recently unearthed remains of a hominid from what is now Serbia. The remains -- a fossilized jaw and teeth -- date to at least 113,000 years ago.
"The specimen is primitive and does not show any Neanderthal-derived traits," lead author Mirjana Roksandic told Discovery News. "It could be a simple case of one non-representative member of a larger population that is morphologically primitive, or a representative member of a more primitive population that remained in the Balkans while Neanderthals developed in the rest of Europe." Roksandic, an associate professor of anthropology at the University of Winnipeg, and her team have not, however, ruled out that the individual belonged to a new Homo species. Europe appears to have been home to several such species over the past 1.7 million years, including Homo georgicus, Homo antecessor, Homo heidelbergensis and Homo neanderthalensis.
For the study, the researchers performed a CT scan and other analysis of the jaw and teeth that were discovered at Mala Balanica Cave in Serbia. Co-author Dusan Mihailovic told Discovery News that "a rich tool assemblage" was found in an upper part of the geological sequence at the site. Additional excavation work may uncover older tools, he said.
The cave complex is located in a Central Balkans region that has been called a "hotspot of biodiversity." "Hotspot of biodiversity as a characteristic of the Balkans was put forward by biogeographers to indicate that most of the plant and animal species that repopulated the continent after glaciations came from the Balkans," Roksandic explained. "In the north of the continent all species of the eastern, and a fair number of the western, part are from the Balkans source." It remains unclear whether or not a new human species originated in the Balkans. This region was never very isolated, as its southern portion remained open throughout the Pleistocene. The new Homo discovery is therefore all the more puzzling.
The researchers cannot conclude much about its possible appearance and behavior, but they can tell it possessed a large jaw and small teeth relative to other known human fossils. Muscle markings associated with the jaw "are not prominent," according to Roksandic.
The fate of Neanderthals and the Serbian individual's group remains unclear, but prior research has determined that modern humans did interbreed, at least to some extent, with Neanderthals. Other anthropologists have suggested that modern humans also may have interbred with additional Homo species from Europe. "It would probably be best to describe Neanderthals and other Pleistocene humans as morphospecies," Roksandic said. "This acknowledges differences but does not discuss their phylogenetic relationship. They are morphologically different, (so) would it prevent them from recognizing each other as potential mates? Hard to say." She added that according to some researchers it takes more than 2 million years to achieve complete genetic incompatibility between species. The various prehistoric human groups may therefore have enjoyed connections despite their anatomical and behavioral differences.
Fred Smith, chair of the Department of Sociology and Anthropology at Illinois State University, told Discovery News that Roksandic and her team "have done excellent work on this site and specimen." Smith, however, questions the possibility that the remains are of a new human species, since he wonders if "they are actually older than the current dating suggests. Furthermore, there is a wide range of variation within Neanderthals, so it is not impossible that the Mala Balanica mandible is part of that variation." Such questions may be answered in the future, as Mihailovic hopes future excavations will take place in Greece, Romania, Bulgaria and other parts of the Balkans. Over the past 10 years he and his colleagues have identified more than 100 caves with potential Paleolithic sediments in Serbia and Montenegro alone.
The discovery of a 1.4-million-year-old hand-bone fossil reveals that the modern human ability to make and use complex tools may have originated far earlier than scientists previously thought, researchers say.
A critical trait that distinguishes modern humans from all other species alive today is the ability to make complex tools. It's not just the extraordinarily powerful human brain, but also the human hand, that gives humans this unique ability. In contrast, apes — humans' closest living relatives — lack a powerful and precise enough grip to create and use complex tools effectively.
A key anatomical feature of the modern human hand is the third metacarpal, a bone in the palm that connects the middle finger to the wrist.
"There's a little projection of bone in the third metacarpal known as a "styloid process" that we need for tools," said study lead author Carol Ward, an anatomist and paleoanthropologist at the University of Missouri."This tiny bit of bone in the palm of the hand helps the metacarpal lock into the wrist, helping the thumb and fingers apply greater amounts of pressure to the wrist and palm. It's part of a whole complex of features that allows us the dexterity and strength to make and use complex tools." (In Images: The Oddities of Human Anatomy)
Until now, this styloid process was found only in modern humans, Neanderthals and other archaic humans. Scientists were unsure when this bone first appeared during the course of human evolution. (The human lineage, the genus Homo, first evolved about 2.5 million years ago in Africa.)
"We had thought the modern human hand was something relatively recent, maybe something that appeared as a recent addition near the origin of our species," Ward told LiveScience.
Now, researchers have discovered a fossil almost 1.5 million years old that possesses this vital anatomical feature, meaning it existed more than 500,000 years earlier than it was previously known to have existed.
"This suggests this feature might be fundamental to the origin of the genus Homo," Ward said.
The scientists discovered a third metacarpal bone in northern Kenya, west of Lake Turkana. The fossil was found near the sites where the earliest Acheulean tools — named for St. Acheul in France where tools from this culture were first discovered in 1847 — were unearthed. The Acheulean artifacts were the first known complex stone tools, rough hand axes and cleavers that first appeared some 1.8 million years ago.
Researchers have discovered a 1.42-million-year-old hand fossil that possesses the styloid process, a vital anatomical feature that allows the hand to lock into the wrist bones, giving humans the ability to make and use complex tools.University of Missouri
"It's an arid badlands desert area now," Ward said. "There's not much vegetation to cover up fossils — there's cobble and rock everywhere, and we try and find fossils by going out and looking under all that cobble and rock on the surface."
The hand-bone fossil is about 1.42 million years old. The researchers suspect it belonged to the extinct human species Homo erectus, the earliest undisputed predecessor of modern humans.
"Back then, this area was an open woodland area much more lush than today, probably with some trees and some areas of grassland," Ward said. "The fossil was found near a winding river, which often deposits things like fossils."
By revealing the early human lineage had a modern handlike anatomy, the fossil "suggests this feature may have a pre-adaptation that helped set the stage for all the technology that came later," Ward said.
Intriguingly, "at this time, in addition to early members of Homo, there were some late-surviving members of Australopithecus still around — close relatives of humans that don't seem to have this adaptation," Ward said. "This raises the question of how important our hands were in the success of our lineage and the extinction of their lineage (Australopithecus)."
The researchers now want to find older hand bones "to see when this feature evolved," Ward said. "We want to get closer to 2 million years ago to find out when this transition to modern hand anatomy took place."
Ward and her colleagues detailed their findings online Dec. 16 in the journal Proceedings of the National Academy of Sciences.
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