Paleoanthropologists have always used to visualize the famous skeleton of the human ancestor found 40 years ago as a petite female because of the size of the bones.

But now with the classification of a variety of specimens as Australopithecus afarensis, some researchers have said that the determination a fossil's gender is harder than they thought.

In a news release, Penn State anthropologist Philip Reno said that they can’t really determine sex of Australopithecines.

On Tuesday, in the open-access journal PeerJ, Reno and Kent State evolutionary biologist C. Owen Lovejoy reported that there are such kinds of size variations in the long-extinct species' bones that the scientists shouldn't assume the smaller-sized skeletons belonged to females.

The Gender-related differences in size are known as sexual dimorphism. Gorillas are highly dimorphic, whereas humans and chimpanzees are only moderately so.

The newly published analysis which was based on a study of over 40 specimens, has found that Australopithecines were more like humans than like gorillas when it came to size differences.

Anthropologist think that Lucy used to stand about 3-foot-6 (107 centimeters) in height, while a more recently found specimen nicknamed Kadanuumuu stood about 5-foot-6 (168 centimeters) tall.

Kadanuumuu, meaning ‘Big Man’ in Ethiopia's Afar language is thought to have been a male of the species, but according to Reno and Lovejoy the two individuals were merely on the lower and upper ends of the Australopithecene size range, with many sizes in between.

Thus, they argued that size isn't a reliable yardstick for the separation of the Lucys from the Brucies. However, other paleoanthropologists will probably question that conclusion.

According to researchers from Penn State and Kent State University, Lucy and other members of the early hominid species Australopithecus afarensis were most likely similar to humans in the size difference between males and females.