While the differences between modern humans and Neanderthals may seem obvious in terms of appearances and physiology, the two species are actually very similar from a genetic standpoint. Physiological differences aside, new genetic findings have uncovered key genetic differences between the two species.

Today, modern humans are known to carry Neanderthal genes. Scientists first found out about the fact after the Neanderthal genome was decoded. These genes are indisputable proof that humans and Neanderthals interbred sometime in the past. New research on the Neanderthal epigenome has also brought about novel and interesting theories about modern human characteristics such as physiology and brain size.

Scientists estimate that human and Neanderthal DNAs are around 99.8 percent similar. However, the key difference between the two species was brought about by the "flipping" of certain genetic switches. These genetic switches are controlled by the epigenome and the latest studies on the Neanderthal epigenome have put forward possible answers to why the two species are so different despite their shared genetic similarities.

The new research was conducted by an international team of researchers led by scientists from the Hebrew University of Jerusalem in Israel. The team was able to accurately map out the epigenetic landscape of three different species including Neanderthals, modern humans and another extinct early human species called the Denisovans. By comparing the epigenetic maps of the three species, the scientists zeroed in on a number of important differences. The researchers published their findings in the online peer-reviewed journal Science.

"This study provides insight into the epigenetic landscape of our closest evolutionary relatives and opens a window to explore the epigenomes of extinct species," the study says.

One of the most glaring differences between the three species is related to disease, specifically, mental and neurological diseases. This discovery adds further credence to the fact that one of the most significant differences between modern and early humans lies in the brain. While the three species shared a common ancestor more than half a million years ago, humans proceeded down an evolutionary path involving marked changes in the way their brains work.

Liran Carmel, a scientist from the Hebrew University of Jerusalem and the lead researcher of the study, says that there is a possibility that common neurological disorders such as Alzheimer's disease, schizophrenia and autism may be strange side effects of the changes that the human brain went through in the course of its development.