Most of us are familiar with "Lucy," the famous hominid skeleton discovered by Donald Johanson and colleagues back in 1974 along a dried out gully in Ethiopia. Lucy lived over 3 million years ago and was assigned the name Australopithecus afarensis; a species many believe led to the rise of Homo sapiens. But a new discovery may rewrite our origins, for it seems Lucy was not the only type of Australopithecine roaming the African plains so long ago.
Researchers at the Cleveland Museum of Natural History recently announced a new species of Australopithecine that lived between 3.3 and 3.5 million years ago, around the same time Lucy and her relatives inhabited the continent. They have dubbed the new species Australopithecus deyiremeda, based on a jaw fragment that contained 5 well-preserved teeth. And as with each new discovery, the convoluted tree of human evolution grows that much bushier.
It was once thought that the evolution of Homo sapiens followed a linear path. After splitting from a common ancestor around 6 million years ago, humans went one direction, chimps went another and a succession of ancestors gradually gave rise to us moderns. But each year, that straight line is further fractured by new discoveries that prove the path to modern humans was anything but straight.
In fact, A. deyiremeda is not the first to be considered a contemporary cousin to Lucy. Australophithecus fossils were discovered in 1995 by researchers from the University of Witwatersrand, who have tentatively named what they believe to be a new species, A. prometheus. New dating of the rocks that held the remains indicate a date of 3.67 million years old - placing it right in Lucy's neighborhood. But not everyone agrees.
The naming of new species has always been a contentious subject. Typically, paleoanthropologists - those tasked with sorting out our complex evolutionary tree - fall into two schools: the lumpers and the splitters.
Lumpers tend to assign species to well-established genera, keeping the number of ancient ancestors to a rather narrow list of candidates. Splitters tend to divide species into ever-expanding categories, based on subtle differences in the skeleton, such as variation in tooth shape or different dimensions of the skull.
Which camp is right? No one knows for sure. But it's apparent the family tree is a lot more complicated than we ever could have imagined.
So the quest continues and the arguments rage on. New fossils will be discovered, new names will be proposed, and scientists will continue to haggle over just how we humans came to be.
