A majority of the genes that can cause diseases in humans were already in existence at the origin of the first cells, German researchers have revealed.
Tomislav Domazet-Loso and Diethard Tautz from the Max Planck Institute for Evolutionary Biology in Plon systematically analysed the time of emergence for a large number of disease genes uncovered by the Human Genome Project using a novel statistical method called "phylostratigraphy".
The researchers said that their analysis allowed them to determine the point of origin for the genes by tracing the last common ancestor in which they gene existed.
They found that the vast majority of the genes traced back to the origin of the first cell.
Other large groups emerged more than one billion years ago around the first appearance of multi-cellular organisms, as well as at the time of origin of bony fishes about 400 million years ago.
The team got surprised to see that there was almost no disease-associated genes among those studied that emerged after the origin of mammals.
According to them, the new findings suggested that genetic diseases affected primarily ancient cellular processes, which emerged already during the early stages of life on Earth.
Based on their observations, the researchers came to the conclusion that all living organisms these days would be affected by similar genetic diseases.
The researchers further said that their findings also suggested that genetically caused diseases would never be beaten completely, as they are linked to ancient evolutionary processes.
While many disease-associated genes are known to occur in other organisms distant to humans like fruitflies and the round worm Caenorhabditis, the new study has for the first time shown that this is systematically true for the vast majority of these genes.
The team conceded that they were yet to uncover why the more recently evolved genes do not tend to cause diseases when mutated.
They, however, insisted that their findings had some practical consequences, for they might make it easier to identify candidates for further disease genes, in particular for those involved in multi-factorial diseases.
The findings are also significant because they confirm that the functional knowledge gained about such genes from remote model organisms is also relevant for understanding the genes in humans.