After reading a number of books by Dr. F. Collins, Dr. D. Venema, Dr. J. Swamaidass as well as looking at numerous articles and videos from BioLogos, on ERVs as evidence of common descent, there are some questions that remain open:
My understanding is that most primates share some ERVs at the same loci in genome. This is used as strong evidence of common descent.
Questions about this:
Is my assumption correct that all humans and all Chimpanzees share some ERVs at the similar loci in the genome?
When a RV infection occurs in a species, I assume it occurs in a subset of the species population as a whole. In other words, it is impossible for the entire species to get the same RV in the same loci at the same time. Is this correct?
My understanding is that some ERVs are shared by all humans and all Chimpanzees. How does a ERV propagate to an entire population of a species?
Also correct. A particular RV insertion occurs in a single individual of the species.
The same way every other mutation (which also occurs in a single individual) propagates to the entire population: very slowly, over many generations. Usually this is a result of ‘genetic drift’, the random increases and decreases in the number of copies of a variant as it gets passed on, generation by generation. To be concrete… the individual in whom the insertion first occurred might pass it on by chance to one offspring, or to two, or to zero. If it is passed on, the same thing happens with each copy in the next generation. Eventually everyone in the population can end up with it.
This process is slow and uncommon. If there were 20,000 individuals in the ancestral population leading to humans and chimps in which the insertion occurred, on average 39,999 insertions were lost to genetic drift for each one that ended up in the entire population. And the ones that did succeed took on average 80,000 generations to do so.
Those keywords help explain various processes at work. I would suggest looking at it from a fauna standpoint.
The flora tree of life is very different. It often contains lots of subspecies that became its own species over time being reunited with its loving ancestors and have a new subspecies born with crazy loops. It’s less common in fauna.
