Tim Bromage, an adjunct professor at New York University College of Dentistry, has reconstructed a skull belonging to the species Homo rudolfensis, which was discovered in Kenya in 1972.

Bromage used a deformable cast and computer-generated models to create replicas of the skull that could be shaped.

The analysis suggests that the specimen had a smaller brain than scientists had believed as well as a distinctly protruding jaw.

But other experts expressed skepticism about Bromage's argument that the repositioning of the specimen's face means its brain size must have been smaller.

"It's probably right that the face should stick far more forward. But to say that because they've changed the angle of the face, the brain size has to get smaller doesn't make any sense," said Robert Martin, a biological anthropologist at the Field Museum in Chicago, Illinois.

"The [specimen's brain] certainly isn't as small as [Bromage is] now arguing."