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Brian Villmoare's cast of the jaw bone. (Photo by Seth Love)
Brian Villmoare's cast of the jaw bone. (Photo by Seth Love)

UNLV Researcher Helps Unearth 2.8 Million-Year-Old Jaw Bone

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With some patience, and a little luck, a research assistant working with the Human Origins Project unearthed a piece of a jawbone with but five teeth, a few molars and a skewed premolar, out of literally hundreds of other fossils.

The slender quality of the jawbone, along with the lack of blocky, apelike molars, provides evidence that gets science once step closer toward the shift from ape to human.

The Human Origins Project that Brian Villmoare works with found this small jaw bone in 2013. It belonged to an early hominid, dating to about 2.8 million years ago. As recent addition to UNLV’s anthropology department as an associate professor, Brian Villmoare’s research brought the university a link to global interaction. This global fossil previews the progenitor human genus.

“It does answer one important question, which is, how early did homo arrive?” Villmoare said. “It also suggests there was this fairly rapid transition from an apelike to humanlike state that probably was caused by a change in the climate.”

Villmoare and the Human Origins Project have been in the Ledi-Geru area of the Afar Regional State of Ethiopia since 2002. This region provides regular opportunities for archaeological excavations.

‘Lucy,’ an ancient hominid dating 3.2 million years ago, was found in this region. And this new fossil serves as evidence that Ethiopia keeps revealing important transitional fossils to expand the understanding of the homo genus.

“All fossils are transitional fossils,” Villmoare said.

Each ancient piece of bone, whether it is this jawbone with five teeth or even Lucy Australopithecus Afarensis, which was a nearly half complete skeleton discovered back in 1974, provides an important piece to the puzzle.

Villmoare used what we already understood today to answer what happened during this vital change of the homo genus between 2 and 3 million years ago.

“Before 3 million years ago, the fossil record is pretty good, going back to at least 4.5 million,” Villmoare said. “Human ancestors before 3 million years ago were sort of ape-like. Which means they were partially arboreal, had long arms, relatively short legs, their brains were not much bigger than chimps, and they lived in a forested environment.”

Understanding these apelike ancestors only gives us the starting point. This understanding arches over paleo-archaeology since Lucy was found in the 70s, as this created the Human Origins project.

Villmoare and the Human Origins project only have about a million years of data to sift through, if it has not already eroded away.

“In the human fossil record there has always been a gap, and the gap was from roughly 2 million to 3 million years ago, a million year gap,” Villmoare said. “Then after 2 million years, ‘they’ are living in the open, with big brains and stone tools. So, that means the gap between 3 and 2 million years is pretty important. It just didn’t happen to preserve in the geology virtually anywhere, and it seems to have eroded away everywhere we have been.”

At least that is what the last ten years show. Ten years of sifting through sand day after day in the hot sun, knowing that a shower is not in the forecast, for there is only enough water to drink. However, success does not come in a void, and great trials bring great rewards.

“It is hard to find the spot to look for that will answer, when did this major shift from apelike to human-like lifestyle happen?” Villmoare said. “We found a place with a lot of fossils, but there are a lot more non-human fossils than human fossils.”

However, we have used our current understanding of apes to further focus the view of our ancient ancestors.

“Apes use their teeth as their tools,” Villmoare said. “When they open a fruit, it is not like an apple. Native fruits are much tougher, so they use their big incisors to peel the fruit, and they use their canines as weapons.”

The teeth of these primates evolved for their purpose. Gorillas, for example, use their large honing canines to crush vegetation.

“We no longer do either of those things, so that allows the teeth to get smaller,” Villmoare said. “The same goes in the back, if you are grinding up hard seeds with your teeth, you need much wider, heavier molars.”

Think of a cow, or a horse, they do not have many teeth in the front. Their incisors work to cut the grass from the ground, and then their molars grind it up.

“But if you are preprocessing things with a tool in some way,” Villmoare said. “When you cut a steak, you don’t need carnivorous teeth anymore to cut a steak.”

Villmoare believes we now need an example of tool usage of about the same time period to help infer why the jaws and brain sizes began to change in our ancient ancestors. Tools defined our genus in the past, and they continue to do so today. Such menial tasks as cutting a steak influence our own evolution.

“We don’t have any stone tools, but we are looking for them,” Villmoare said.

The closest fossil record that has tools is about 2.6 million years ago.

“If we can bridge the gap between 2.6 million years ago and 2.8 million years ago with tool use, we can then infer why our dentition changed,” Villmoare said.

The increase in tool use is most likely related to the drastic shift in climate.

“We have a very different climate at our site in 2.8, then you find at 3,” Villmoare said. “At 3 it is wet and forested, and at 2.8 it’s dry, like the Serengeti.”

Barbara Roth, chair of the anthropology department, agrees that the purpose of anthropological research is to use the past, as Villmoare has done, to inform our present and future.

“To learn about the past, and about human adaptation and behavior,” Roth said. “We are very excited because this is an important find.”

Excitement like this may not be instantaneous. It was almost 3 million years in the making. It has already endured time.

But against fighting time, especially against the knowledge of the ancient past, is always an uphill battle.

Fortunately for UNLV, one of the lead researchers of this find, Kaye Reed, will be on campus giving a talk titled, “Paleoanthropology of the Ledi-Geraru, Ethiopia: New Evidence for habitat change in the Afar between 3.4 – 2.8 MA.”

Reed’s presentation will be on April 27th from 11:30 a.m. to 12:30 p.m. in room 212 of the Frank and Estella Beam hall.

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