A team of researchers have described the developmental processes that distinguish modern humans from Neanderthals for the first time. Human's flat faces are caused by bone loss after the time of Neanderthals.

Researchers from New York University's College of Dentistry found that modern humans have flatter faces compared to early ancestors. The oddly flat and oval facial features are much different than the features ancient men possess.

Neanderthals who existed more than 200,000 years ago are distinct from modern humans because of their heavy eyebrows, large noses and think skulls. They inhabited much of Europe and parts of Asia. However, they died around 40,000 years ago. So why do humans today have strangely flat and oval facial features?

In the study published in the journal Nature Communications, the researchers aimed to distinguish Neanderthal's faces from modern humans. Using several well-preserved Neanderthal skulls of a child found in 1926 in France, they mapped bone and cell growth processes that occurred in the outer layer of bones from Neanderthals buy using an electron microscope and a portable confocal microscope.

"Cellular processes relating to growth are preserved on the bones," Dr. Timothy Bromage of NYUCD's Department of Biomaterials said.

Findings show that facial and bone growth remodelling, a process wherein the bone is deposited and reabsorbed before forming the adult bone, contributed to the development of a prominent maxilla. This is because of widespread deposits by osteoblasts without a compensatory resorption.

"We always considered Neanderthals to be a very different category of hominin," Dr. Rodrigo Lacruz, assistant professor in the Department of Basic Science and Craniofacial Biology at New York University's College of Dentistry (NYUCD) said.

He added that modern humans strayed from the ancestral pattern. The next stage of their research is to determine how and when humans developed their facial growth plan.

"The growth remodelling identified in these fossil hominins is shared with Australopithecus and early Homo but not with modern humans suggesting that the modern human face is developmentally derived," the researchers wrote in their paper.

"Our results show that Neanderthals and SH hominins show extensive bone deposition over the maxilla, a process associated with midfacial prognathism. This is different from the resorption that dominates over the retracted human maxilla," they added.

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