10 Extinct Hominids

Ardipithecus Ramidus
Ardi's skeleton suggests she and her family were both bipedal and tree dwellers. T. Michael Keesey/Used under Creative Commons CC BY 2.0 License/Flickr

It's an exciting time for archaeology because we're still discovering fascinating artifacts and fossils that clue us in to the history of hominids. As recently as 2009, archaeologists found "Ardi," a surprisingly intact skeleton of the species Ardipithecus ramidus, one of the earliest known species of extinct hominids. Ardi and her family existed about 4.5 million years ago in what is now Ethiopia [source: Roberts].

Paleoanthropologists are interested in studying how our hominid ancestors moved. Specifically, they'd like to pinpoint when and how bipedalism developed, which is a significant advancement that distinguishes us from our primate ancestors because it is more energy efficient than walking on four limbs.

Finding so much of Ardi's skeleton, rather than just the skull and teeth of the species we had found before, was a major discovery. It revealed much of Ardi's body structure. Ardi's arms and fingers were long with short palms and wrists that were likely flexible. The pelvis was short and broad, and the feet could both grasp and support bipedalism. All of this suggests that Ardi climbed trees, could probably walk on two feet and didn't use her knuckles for walking much [source: Roberts].

Other environmental evidence suggests Ardi lived among trees and shrubs, which called into question the prevailing theory at the time that bipedalism developed on the savanna [source: Smithsonian].

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