Big-Toothed Prehistoric Human Lived Alongside 'Lucy'

The human family tree has a new member: a big-toothed early human ancestor that lived in Ethiopia 3.3 to 3.5 million years ago, according to a paper in the latest issue of the journal Nature.

The newly discovered human, named Australopithecus deyiremeda, overlapped in both time and region with yet another prehistoric human, "Lucy" (Austrolithecus afarensis). The find is strong evidence for the presence of more than one closely related early human ancestor species prior to 3 million years ago.

Because this particular species' teeth had super thick enamel and its jaws were built to last, "it probably engaged in heavy chewing and consumed harder, tougher, and more abrasive dietary resources," lead author Yohannes Haile-Selassie, curator of physical anthropology at The Cleveland Museum of Natural History, told Discovery News.

Photos: Faces of Our Ancestors

Haile-Selassie and his team analyzed the remains, which were collected from the central Afar region of Ethiopia. Combined results from three established different dating processes yielded the estimated age of the fossils.

The location where the fossils were found is just 21.8 miles south of where "Lucy" lived in Hadar, Ethiopia. The researchers think the species could have lived in even closer proximity. The two might have co-existed, which would be like Homo sapiens now sharing turf with another type of human.

While such a scenario today seems unfathomable for humans, it was likely common back in the day.

As for why, Haile-Selassie said, "There is some evidence that during the middle Pliocene time period (about 3.3 million years ago) when multiple hominins (early humans) were running around, there were rivers supporting gallery forests that laterally extend to woodlands and grasslands."

"It was an ecosystem that supported numerous and varied habitats," he continued. "With niche partitioning, a number of related taxa can co-exist in such an ecosystem."

Photos: What Did Prehistoric Humans Eat?

Anthropologists debate about which species is the stem of Homo sapiens, meaning that it should be positioned at the very bottom of the human family tree. Candidates now include two other early humans, Ardipithecus ramidus and Australopithecus anamensis, but it could also be an as-of-yet undiscovered species.

Whichever it was, the stem species, via evolution and divergence, could have later resulted in more than 20 different types of humans, including Homo sapiens.

In terms of what happened to this crowded field of early relatives, Haile-Selassie said, "Some of them gradually gave rise to a new form and went extinct. Others went extinct with no descendants."

He added, "When the environment changes and their habitat diminished, or when they faced harsh competition with others for resources and failed to be good competitors, they had no alternative but extinction."

The fossil evidence for the earliest anatomically modern humans comes from Ethiopia, so it cannot be ruled out that A. deyiremeda and/or "Lucy" is our direct ancestor.

Sophisticated Tool Kit Predates Humans

Other than what the tooth and location evidence might reveal about their diets and habitats, little is known about the culture of such early humans. Intriguingly, a collection of stone tools dating to 3.3 million years ago was recently found at a site called Lomekwi 3 in Kenya. For now, though, the maker of those relatively sophisticated tools–consisting of anvils, hammers and more–remains a mystery.

Yet another mystery is a 3.4-million-year-old partial foot found by Haile-Selassie and his colleagues in the same region of Ethiopia where A. deyiremeda was discovered. Could it have belonged to yet another different type of human?

That remains to be determined. What's clear, for now, is that East Africa was bustling with early human activity long before our species ever evolved.

"It is remarkable to have two closely related species that appear to have lived in the same area, during approximately the same time period," said Fred Spoor of both the Max Planck Institute for Evolutionary Anthropology and University College London, and author of a "News & Views" article in Nature about the find.

"This raises the important question whether and how they differed in their behavior, diet or other ways that made long-term co-existence possible."

Shown are casts of the jaws of

Back in the Beginning

To put a human face on our ancestors, scientists from the Senckenberg Research Institute used sophisticated methods to form 27 model heads based on tiny bone fragments, teeth and skulls collected from across the globe. The heads are on display for the first time together at the Senckenberg Natural History Museum in Frankfurt, Germany. This model is Sahelanthropus tchadensis, also nicknamed "Toumai," who lived 6.8 million years ago. Parts of its jaw bone and teeth were found nine years ago in the Djurab desert in Chad. It's one of the oldest hominid specimens ever found.

Australopithecus afarensis

With each new discovery, paleoanthropologists have to rewrite the origins of man's ancestors, adding on new branches and tracking when species split. This model was fashioned from pieces of a skull and jaw found among the remains of 17 pre-humans (nine adults, three adolescents and five children) which were discovered in the Afar Region of Ethiopia in 1975. The ape-man species, Australopithecus afarensis, is believed to have lived 3.2 million years ago. Several more bones from this species have been found in Ethiopia, including the famed "Lucy," a nearly complete A. afarensis skeleton found in Hadar.

Australopithecus africanus

Meet "Mrs. Ples," the popular nickname for the most complete skull of an Australopithecus africanus, unearthed in Sterkfontein, South Africa in 1947. It is believed she lived 2.5 million years ago (although the sex of the fossil is not entirely certain). Crystals found on her skull suggest that she died after falling into a chalk pit, which was later filled with sediment. A. africanus has long puzzled scientists because of its massive jaws and teeth, but they now believe the species' skull design was optimal for cracking nuts and seeds.

Paranthropus aethiopicus

The skull of this male adult was found on the western shore of Lake Turkana in Kenya in 1985. The shape of the mouth indicates that he had a strong bite and could chew plants. He is believed to have lived in 2.5 million years ago and is classified as Paranthropus aethiopicus. Much is still unknown about this species because so few reamins of P. aethiopicus have been found.

Paranthropus boisei

Researchers shaped this skull of "Zinj," found in 1959. The adult male lived 1.8 million years ago in the Olduvai Gorge of Tanzania. His scientific name is Paranthropus boisei, though he was originally called Zinjanthropus boisei -- hence the nickname. First discovered by anthropologist Mary Leakey, the well-preserved cranium has a small brain cavity. He would have eaten seeds, plants and roots which he probably dug with sticks or bones.

Homo rudolfensis

This model of a sub-human species -- Homo rudolfensis -- was made from bone fragments found in Koobi Fora, Kenya, in 1972. The adult male is believed to have lived about 1.8 million years ago. He used stone tools and ate meat and plants. H. Rudolfensis' distinctive features include a flatter, broader face and broader postcanine teeth, with more complex crowns and roots. He is also recognized as having a larger cranium than his contemporaries.

Homo ergaster

The almost perfectly preserved skeleton of the "Turkana Boy" is one of the most spectacular discoveries in paleoanthropology. Judging from his anatomy, scientists believe this Homo ergaster was a tall youth about 13 to 15 years old. According to research, the boy died beside a shallow river delta, where he was covered by alluvial sediments. Comparing the shape of the skull and teeth, H. ergaster had a similiar head structure to the Asian Homo erectus.

Homo heidelbergensis

This adult male, Homo heidelbergensis, was discovered in in Sima de los Huesos, Spain in 1993. Judging by the skull and cranium, scientists believe he probably died from a massive infection that caused a facial deformation. The model, shown here, does not include the deformity. This species is believed to be an ancestor of Neanderthals, as seen in the shape of his face. "Miquelon," the nickname of "Atapuerca 5", lived about 500,000 to 350,000 years ago and fossils of this species have been found in Italy, France and Greece.

Homo neanderthalensis

The "Old Man of La Chapelle" was recreated from the skull and jaw of a Homo neanderthalensis male found near La Chapelle-aux-Saints, in France in 1908. He lived 56,000 years ago. His relatively old age, thought to be between 40 to 50 years old, indicates he was well looked after by a clan. The old man's skeleton indicates he suffered from a number of afflictions, including arthritis, and had numerous broken bones. Scientists at first did not realize the age and afflicted state of this specimen when he was first discovered. This led them to incorrectly theorize that male Neanderthals were hunched over when they walked.

Homo floresiensis

The skull and jaw of this female "hobbit" was found in Liang Bua, Flores, Indonesia, in 2003. She was about 1 meter tall (about 3'3") and lived about 18,000 years ago. The discovery of her species, Homo floresiensis, brought into question the belief that Homo sapiens was the only form of mankind for the past 30,000 years. Scientists are still debating whether Homo floresiensis was its own species, or merely a group of diseased modern humans. Evidence is mounting that these small beings were, in fact, a distinct human species.

Homo sapiens

Bones can only tell us so much. Experts often assume or make educated guesses to fill in the gaps in mankind's family tree, and to develop a sense what our ancestors may have looked like. Judging from skull and mandible fragments found in a cave in Israel in 1969, this young female Homo sapien lived between 100,000 and 90,000 years ago. Her bones indicate she was about 20 years old. Her shattered skull was found among the remains of 20 others in a shallow grave.