Sunday, 13 February 2011
How Did Lucy Walk?
A reconstruction of Lucy at the Natural History Museum in London.
A paper recently published in the journal Science on the discovery of the metatarsal bones (the long bones connecting the toes to the rest of the foot) of Australopithecus afarensis has given rise to many kinds of headlines in the popular press. In the wildest scenario, we see a high heeled Lucy walking down a city street without attracting any attention from the other city dwellers.
It is good to remember that researchers have debated Lucy’s bones for over 35 years.
Paleoanthropologists Carol Ward of the University of Missouri and Donald Johanson of the University of Arizona analysed 35 fossils assumed to be A. afarensis specimens that were discovered in the past 15 years in Hadar, Ethiopia. They believe that the fourth metatarsal shows that Lucy was not flat footed but could almost walk like modern humans.
According to Ward, the bone suggests that when its one end touched the ground, the other formed an angle of eight degrees with it, functioning like a shock absorber.
Donald Johanson belonged to the research team that discovered the first A. afarensis remains in 1974 so this might cause him to see Lucy as a very special link leading to modern man.
The history of paleoanthropology knows surprisingly many cases in which the discoverer of a fossil believed that it was the find of the century.
Not all paleoanthropologists share Ward’s optimism. ScienceNOW mentions the dissenting view of Will Harcourt-Smith of the American Museum of Natural History in New York:
“Although he agrees that A. afarensis had some arching, it may have lacked the most important arching on the inside of the foot. Lucy's fingers and toes also were more curved than those of living humans and her shoulder was more apelike—traits useful for tree-climbing.”
According to Harcourt-Smith, Lucy would have been more at home in trees than on the open ground.
Once again, it seems that the headlines do not match reality. We cannot even be sure that the foot bones belong to A. afarensis although they were dated at roughly the same age as the ”original” Lucy found in 1974.
Usually, researchers do not date fossils but they date the ground below or around them, which makes radioactive dating somewhat unreliable.
The assumptions behind the methods also lessen their reliability.
Gibbons Ann. 2011. Lucy Had a Spring in Her Step. Science NOW (10 February).