Please feel free to ask more questions.....
Question: Surely, if there was a gene that codes for immortality, and this has been inactive for millions of years, it would have mutated over time and eliminated into oblivion
Answer: The ELPIs hypothesis does not explicitly refer to a definite 'immortality' gene on the genome. It merely suggest that there is 'a mechanism' that acts against ageing. Current knowledge suggest that this may involve the DNA molecule, but according to one of the hypothesis' principles, the technology is yet to be discovered. In any case, there are examples of genes that have remained unchanged, and still active on our genome for millions of years:
1. The genes for developing a tail. This ability is encoded in the foetal development and active, but new genetic controls have been added during evolution to overwrite it. The genes exist but their action is suppressed or inhibited. Human embryos have tails when a month old. Then the tail regresses and disappears through action of newer genetic controls, causing apoptosis and remodelling. This regulation is under the control of Hox10 and Hox 11 master regulatory genes (http://scienceblogs.com/pharyngula/2007/09/the_hox_code.php).
2. The genes for developing webbed digits. This is the same principle as above. The genes exist but their function or action is suppressed at a late stage of development. Examples of genes coding for fusion of digits in humans are 2q34 or 7q36.
3. Non-retroviral RNA elements (Horie M, Honda T, Kobayashi Y et al. Endogenous non-retroviral RNA virus elements in mammalian genomes. Nature, 2010, 463(7277);84-87). It has been shown that elements homologous to the nucleoprotein gene of bornavirus are found in the genomes of many mammalian species including humans, and that these have been formed more than 40 million years ago. These elements are active today. If these elements have remained unchanged and can be currently active in the human genome, then it becomes more likely that other genes may have the same fate.
Question: How is it possible that such immortality gene, although inactive, has the ability to function properly after such a long time?
Answer: Although it is true that DNA in the long term can spontaneously decay, it is not impossible for genes to show evidence of repair. It is known that ancient bacteria, although dormant for millions of years, exhibit evidence of active repair to their DNA. Therefore, if a mechanism exist for active DNA repair in ancient bacteria, it is logical to assume that such a mechanism could exist for repair of other DNA (such as in humans). In a paper (Stewart Johnson S, Hebsgaard MB, Torben R et al. Ancient bacteria show evidence of DNA repair. Proc Nattl Acad Sci USA, 2007, 104(36): 14401-14405) it has been shown that bacteria in 500,000 year-old samples can survive by using active DNA repair. The reason why some bacteria have been found to be viable after so many millions of years is not that they are biologically dormant and biologically inactive, thus suffering less damage. They are viable, because they exhibit active DNA repair.
Question: Is it reasonable to assume that an immortality mechanism currently operates but is not fully active, and it is repressed or inhibited?
Answer: Yes. It is possible that there are existing genes on the genome that have this capability but their current function remains sub-optimal or minimised. It could be that there are also existing molecules or factors that can operate against ageing but currently function sub-optimally. These may need to be activated to make them work at full capacity. Immortalisation mechanisms operate fully in germ-line cells but not in somatic cells.