It is generally believed mitochondrial dysfunction contributes to the aging process. As mitochondria age, they develop mutations which makes them less efficient at producing energy and causes them to spill increasing amounts of reactive oxygen species (ROS) into the cell damaging it on the whole.
It has been known that plant mitochondria harbor what it called selfish DNA. This is mitochondrial DNA that replicates excessively causing harm to its parent cell and conferring no obvious benefit.
For the first time researchers have thoroughly described and characterized this DNA in animals. In the study it was shown that c. elegans nematodes have selfish DNA. Large segments of DNA sequences harboring deletions were observed and found to be generationally inherited in the animals.
It was also found that the worms with selfish DNA appeared older; they had less offspring and less muscle activity.
The study also showed that selfish DNA was surprisingly not removed by natural selection, even though it clearly put those animals possessing it at an adaptive disadvantage.
The authors conclude:
The extent to which selfish mtDNA threatens other animal species is also unknown. We speculate that selfish mtDNA in animals, though sometimes characterized as rare, might be more widespread but has remained a cryptic phenomenon owing to difficulties in discovering heteroplasmic selfish mtDNA variants, demonstrating transmission advantages, and characterizing phenotypic effects of particular mtDNA elements.
Conceivably selfish DNA if it exists in humans may play a role in accelerated aging and development of disease, and may be something important for science to look for.