Archaeologists discover oldest hominid skeleton

On Oct. 1, researchers revealed a skeleton in their closet. After 17 years of extensive research, Ardi, a 4.4 million-year-old hominid, replaces Lucy as the oldest remnant of early human evolution by approximately 1.2 million years.

In November of 1992, two pieces of Ardi's palm were discovered in the Middle Awash region of Ethiopia, an area that proved to be quite rich in historical artifacts. In fact, the site at which Lucy was found more than 30 years ago is only 45 miles away. Ever since, researchers have scrambled to find the remains of Ardipithecus ramidus, or "Ardi" for short. They ultimately unearthed 125 bone fragments, a rare wealth of information. But the bones were in need of reassembling. The skull alone was in 60 parts.

Ardi was assembled using digital reconstruction. "Tim [White] showed me pictures of the pelvis in the ground, and it looked like an Irish stew," Alan Walker said, a paleoanthropologist from Penn State, in an interview with Time magazine.

Her bones were so delicate that they would disintegrate upon touch. Scientists used a needle and microscope to disengage them "millimeter by submillimeter," as the researchers described the process.

Although quite a bit of archaeological evidence had been amassed over the years, researchers refrained from discussing the findings with the public, even though they predated other findings that were being made during that time.

Archaeologists at the excavation site were also able to uncover over 6,000 remains from Ardi's habitat. These precious fossils included the bones of 36 individuals of the same species. In addition to the human bones, there were also fragments of plants and animals from the same time period, all suspended between two sediment layers of volcanic ash.

Using these remnants as clues, scientists were able to piece together Ardi's world. They concluded that she lived in a humid woodland, lined with fig and palm trees. She was among various species of monkeys and birds. However, Ardipithecus ramidus were mostly herbivores, their diet consisting of fruit and nuts. Amazingly, scientists were able to conclude this based on isotopes found in their teeth.

Once assembled, Ardi resembled an adult female, standing at four feet tall and weighing an estimated 120 pounds. Based on the size of her skull and teeth compared to other fossils found at the site, they were able to determine her gender.

The structure of her pelvis, legs and feet indicate that she walked upright, rather than on all fours, as scientists imagined our early ancestors would. She had a sideways big toe, with which she latched onto trees in order to hoist herself up. Yet it is believed that she mostly stayed grounded.

The structure of her wrist, hand and shoulder reveal that unlike chimpanzees, Ardi did not use her knuckles for walking, nor did she swing from trees.

Ardi exhibited other features that distinguished her from apes. She had a dexterous hand which was significantly more flexible than a chimpanzee's and was capable of grasping objects with her long fingers and opposable thumb. This unique structure allowed her to simultaneously walk and make use of her hands. Furthermore, the flexibility of her wrists allowed weight to be placed on her palms.

Her canine teeth were not sharp, indicating that she did not use them for battle, as monkeys do. Because these teeth were used less for intra-species conflict, researchers speculate that Ardipithecus developed a less competitive social system.

These noteworthy differences between chimps and Ardi disclaim a theory that used to be ubiquitous within the scientific community. This theory points to a common ancestor between apes and humans that resembled a chimpanzee more than it did a human. Ardi's proximity to this common ancestor, paired with her physical traits that unmistakably differ from those of a chimp, suggest that the common ancestor did not resemble an ape at all.

"This skeleton flips our understanding of human evolution," C. Owen Lovejoy, a Kent State University anthropologist and member of the Middle Awash excavation team, said to Time. "It's clear that humans are not merely a slight modification of chimps, despite their genomic similarity."

For now, there is no way of knowing what the common ancestor might have looked like before the lineages diverged. Ardi is the closest hominid fossil we have to the divergence. Ardi's discovery exposes a previously unvisited sector and fills a gap in our knowledge of human evolution.