Significant genetic differences are not only in the DNA sequence (gcttaatgc…), but also in other things that stick above it (epigenetic modifications over the genes). Scientists at the Hebrew University, the Max Planck Institute in Leipzig and the Universities of Oviedo and Cantabria have rebuilt first epigenetic maps Neanderthals and Denisovans, and compared with modern humans. There are 2,000 different genomic regions, including those that house the Hox genes that organize the body of all animals, which explains the morphological differences between the three groups of humans.
The researchers analyzed the genomes of high quality data from fossil bones of two women to call females is somewhat shocking – that lived about 50,000 years ago: A Neanderthal and denisovana. The latter species has been defined in recent years from its fossil DNA, and little is known of their morphology or their geographic extent. The great innovation of this study is that scientists have found a way to infer patterns of gene activation of these two species.
A major epigenetic modifications is the addition of a methyl group (-CH3, one carbon atom and three hydrogen bonds) to one of the letters of the DNA (the c, or cytosine). This methylation activity evolutionarily born as a system to inactivate transposons, ancient virus genomes that have lost their infectivity but retain the move from one place to another by the genome.
Methylation today also serves to inactivate large stretches of human DNA, including an entire X chromosome in females (females have two, or XX, while males only have one or XY). Human development started with the most open d genes, and embryo development involves the progressive deactivation of a gene or other in each body.
Methylation patterns are 99% identical between modern humans and the two former species. Diamonds reside in the remaining 1%, and the jewels in the crown are the two Hox genes whose pattern of activity differs markedly between ancient and modern species. These rows are genes in the genome (the Hox1 to Hox13), and also define consecutive body areas. For example, head, neck, back, lumbar and others; or shoulder, arm, forearm, wrist, palm and fingers.
Methylation changes in these two Hox genes correspond to the morphological differences between ancient and modern humans, such as femur length, the size of the hands and fingers and the width of the elbows and knees.
Can we deduct one day all the characteristics of a species based only on their genome? All signs point to yes.