The distinctive facial and physical characteristics of Neanderthals have been shown to have been a relatively short stepwise evolution that included mating with European homonims. An analysis of all the ancient remains found in the Sima de los Huesos site in Spain serves as evidence to bring an end to an 80 year debate about Neanderthal development according to Juan-Luis Arsuaga, Professor of Paleontology at Madrid's Complutensis University, and colleagues. The study was reported in the June 19, 2014, edition of the journal Science.
The skeletons of 28 individuals from different time frames form the basis for the researcher’s conclusion. Neanderthals developed their distinctive jaw and forehead over a short period of time through adaptation and mating with other early species of hominin that were primarily European. The Sima de los Huesos site is the only site ever found that exhibits an accumulation of both homonin and Neanderthal remains that show a slow but steady evolution of Neanderthals. The excavation of the remains and the analysis has taken the better part of 30 years.
The researchers conclude that one group of early human ancestors ventured out of Africa into Europe about 500,000 years ago. These were the ancestors of Neanderthals. Climate, weather, or geographic changes may have isolated Neanderthal’s early ancestors and allowed this species of human ancestor to evolve independently. Resident species of other early human ancestors mated with Neanderthals and may have introduced the genetic component that eventually led to the demise of Neanderthals through breeding with modern humans.
The study shows that Neanderthals developed their defining physical features in stages. This concept is directly in opposition to a commonly held thought that the development of Neanderthal characteristics occurred quickly and all the defining characteristics of Neanderthals developed together. The researchers note that the shape of Neanderthal’s jaw may have been the result of using the jaw as a third appendage while feeding.