Philosophers of science use the word paradigm (pair – uh – dime) to describe the set of ideas and practices that define a field of scientific inquiry. If you studied human anthropology and evolution in the last few decades you were exposed to the paradigm that humans evolved from an ape-like creature that resembles modern day chimpanzees. You might recall learning about Lucy, the 3 million year old hominid found in Ethiopia that belongs to the genus Australopithecus.
A fossil discovered only 50 miles away from Lucy’s site in Ethiopia is radically changing the way biologists and anthropologists think about human evolution. The new fossil, named “Ardi” by the research team, is the remarkably intact skeleton of a female belonging to the new species Ardipithecus ramidus. Radiometric dating from the site indicates Ardi’s remains are almost 4.5 million years old. The researchers discovered the first piece of Ardi 15 years ago and since uncovering that single tooth, they painstakingly cataloged the remains of more than 30 other individuals from the same species in the area.
The skeletons reveal that this human ancestor was able to walk upright but was also a skilled tree climber. Their teeth suggest that Ardi and her relatives were omnivores, eating a varied diet. The findings suggest that the common ancestor of modern humans and chimpanzees probably looked and behaved more like humans than chimps and gorillas. This new emerging paradigm holds that many of the traits that separate humans from the great apes are evolutionary innovations that arose after the split between the two groups around 6-7 million years ago. In the human lineage, increases in brain size and adaptations for bipedal locomotion appear to be the greatest evolutionary developments.
If these findings hold up to scientific scrutiny, they represent a true paradigm shift. Decades from now people will look back at October 2009 as a point when our understanding of primate evolution changed dramatically. One of the world’s most important scientific journals, Science, devoted 11 separate articles to the discovery in the Oct. 2 issue, an unprecedented number of pages for any recent discovery.
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