An international team of scientists from the US, UK, and Spain have published a finding titled “Ontogeny of the Maxilla in Neanderthals and their Ancestors” in the journal Nature Communications, detailing the differences in the facial growths of Neanderthals and modern humans.
The study was led by Rodrigo Lacruz, an assistant professor in the Department of Basic Science and Craniofacial Biology at New York University's College of Dentistry (NYUCD).
This is the first study to ever examine the differences in the facial growths of Neanderthals and today’s humans. The team of scientists based their study on the fact that the way in which the bones of the faces of modern humans grow is quite different from the way those of extinct Neanderthals grew. Neanderthals lived nearly 300,000 years ago.
"This is an important piece of the puzzle of evolution," said Lacruz, a paleoanthropologist and enamel biologist. "Some have thought that Neanderthals and humans should not be considered distinct branches of the human family tree. However, our findings, based upon facial growth patterns, indicate they are indeed sufficiently distinct from one another.”
The researchers analyzed the morphological processes underlying the differences between the faces of Neanderthals and modern humans in order to fully establish the process of human evolution up to the present period of humanity.
Scientists already established that bone formation occurs when bone-forming cells or osteoblasts deposit bone and bone-absorbing cells or osteoclasts reabsorb bone. Outermost layer of human facial bones were found to contain resorptive fields while those of Neanderthals contained bone deposition – an exact opposite of what obtains with modern man.
The team of researchers utilized an electron microscope and a small confocal microscope invented by co-author Dr. Timothy Bromage of the Department of Biomaterials in NYUCD. These instruments were deployed to map the resorption and deposition – bone-cell growth processes – that occurred in the facial skeletons of Neanderthals.
"Cellular processes relating to growth are preserved on the bones," Bromage said. "Resorption can be seen as crater-like structures – called lacunae – on the bone surface, whereas layers of osteoblast deposits have a relatively smooth appearance."
The well-preserved skulls of Neanderthal children excavated in Gibraltar in 1926 as well as those excavated from La Quina in France in the 1900s were analyzed to differentiate them from the remodeled skulls of Neanderthals that lived about 400,000 years ago and unearthed in the Sima de los Huesos area of Spain.
Ultimately, the researchers found that humans deviated from the facial bone development of Neanderthals many years ago; and the researchers are now committed to knowing exactly when this happened down the ancestral lineage.