The 3 million-year-old fossil skull Australopithecus africanus doesn't belong to ancient humans, a new study suggests. The researchers say that the skull lacks a key feature possessed by modern humans.

The ancient skull of Australopithecus africanus - a young hominin - was found in South Africa some 90 years ago. The researchers had earlier believed that the skull belonged to a human child.

The skull is generally referred to as The Taung Child and was found by Wits University Professor Raymond Dart.

Latest research by scientists at the University of the Witwatersrand shows that the cranial features of the ancient hominin doesn't resemble those seen in modern human children. Specifically, the fossilized skull lacks a "soft spot" that is usually seen in human babies with large heads.

Modern human babies have several bony plates in their skull. These plates fuse later in life to form the hard skull, abc news reported.

Scientists used Microfocus X-ray Computed Tomography (CT) to study the skull in detail. The specimen is considered to be the oldest and best-preserved skull of an early human child. Several theories have tried to explain that the ancient skull has key cranial adaptations found in modern human infants.

"A recent study has described the roughly 3 million-year-old fossil, thought to have belonged to a 3 to 4-year-old, as having a persistent metopic suture and open anterior fontanelle, two features that facilitate post-natal brain growth in human infants when their disappearance is delayed," said Carlson in a news release.

The current study did not find any evidence that support the idea that Australopithecus africanus' brain development was like that seen in humans.

"The results as well as comparisons with the hominin fossil record and chimpanzee variation do not support the hypothesis that the features evolved in A. africanus or early Homo hominins," they report, according to abc news.

The study is published in the journal Proceedings of the National Academy of Sciences (PNAS).