A 400,000-year-old skull found in Portugal is puzzling scientists about the ancestors of modern humans and the evolution of man.

The fossil was found in a 2014 archaeological project in the Aroeira cave area, according to the US National Academy of Sciences specialty journal. This is the oldest human fossil bone ever found in Portugal.

Anthropologist Rolf Quam of Binghamton University, who is also the author of the study, says there is much debate over the origins of this skull.

The 400,000-year-old skull fossil found in the Aroeira cave area. (Source: phys.org)

Based on some bone characteristics, Quam’s team suggested that the skull was not of the Neanderthals, a species of extinct genus, but could belong to the Neanderthals’ ancestors. In addition, scientists have not been able to determine whether the skull is male or female, as well as the cause of death.

However, based on the surface characteristics of the cliffs and surrounding sediments, the team determined that the fossil was about 400,000 years old. Meanwhile, bone structure shows that this is an adult’s skull. According to Portuguese archaeologist Joao Zilhao, the human skull fossils at the Aroeira cave are a rare and significant discovery in archeology.

In the near future, experts will continue to study the details of the skull and the environment of the Aroeira cave area to build a panoramic picture of ancient life as well as human evolution.

This 400,000-year-old fossil will be on display at the National Archaeological Museum in Lisbon this October.