We share over 99% of our genome with Neanderthals. Yet the differences between us and them are pretty huge - from physical appearance, to brain development... and the fact that we're still here and they're not. So, what gives?
A recent comparison of the the 2 genomes - Neanderthal and human - reveals that the differences are not in the sequence of the 3.2Gb (or 3.2 billion bases) of DNA, but in which genes were switched on or off. Hundreds of genes turned on in modern humans, were found to be turned off in Neanderthals. And vice-versa, hundreds of genes turned off in modern humans were turned on in Neanderthals.
This discovery is pretty huge. Termed the epigenome, (which lets us reserve the term "genome" for the actual DNA sequence), this finding demonstrates the power of these on/off switches. You have to marvel at the efficiency of genome organisation and control; all the information needed by the 2 species is already there - we just access different parts of it.
This finding has implications on our understanding of many things with a genetic basis - not just informing us about our evolutionary history. Similar epigenomic effects have also been implicated in various neurological and psychiatric disorders including autism, schizophrenia and Alzheimer's disease.
Hundreds of Neanderthals' genes were turned off while the identical genes in today's humans are turned on