Paleoanthropologists report that foot bones found at the Woranso-Mille site in Ethiopia in 2009 belong to Australopithecus deyiremeda, a species that lived alongside the famous Lucy (Australopithecus afarensis). The fossils are about 3.4 million years old. The Burtele Foot—eight foot bones recovered at the site—was at first hard to assign to a species because naming a species from lower-body parts is unusual; later fieldwork provided more material and a clearer link to A. deyiremeda. The study appears in Nature and received funding from the National Science Foundation and the W.M. Keck Foundation.
Arizona State University paleoanthropologist Yohannes Haile-Selassie led the team that found the foot. University of Michigan geochemist Naomi Levin sampled eight of the 25 teeth from Burtele to study diet. Her isotope analysis indicates that A. deyiremeda ate foods from trees and shrubs, whereas A. afarensis had a broader diet that included tropical grasses and sedges. The team also recovered a juvenile jaw with baby teeth in place and adult teeth forming in the mandible, which suggests similar growth patterns between the species.
Anatomy of the Burtele Foot appears more primitive than Lucy’s foot: it retained an opposable big toe and had longer, more flexible toes suited to climbing. When walking on two legs, A. deyiremeda likely pushed off with its second toe rather than the big toe. Haile-Selassie says the finds show that bipedal walking took multiple forms in early hominins. Levin adds that the fossils reveal how related species used different diets and behaviors to coexist, information that helps explain adaptation to changing climates and rising carbon dioxide levels.
Difficult words
- paleoanthropologist — scientist who studies ancient human ancestorsPaleoanthropologists
- fossil — remains or traces of ancient organismsfossils
- isotope — chemical variant of an element with different atoms
- mandible — lower jaw bone in humans and animals
- opposable — able to move opposite another finger or thumb
- bipedal — moving by walking on two legs
- adaptation — trait or process that helps survive environmental change
- juvenile — young individual not yet fully grown
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Discussion questions
- How do differences in diet and foot anatomy help related species like A. deyiremeda and A. afarensis coexist? Give reasons from the article.
- What does the existence of multiple forms of bipedal walking suggest about early hominin evolution?
- Why are later fieldwork and external funding important for identifying and understanding ancient species, according to the article?
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