Even without a cohesive understanding of genetics, Darwin was able to propose a mechanism for evolution based on phenotypic observations. Developments in microbiology were then able to support the idea of shared common ancestry and descent with modification by comparing the nucleotide sequences in the DNA of different species — the greater the similarities, the more closely the two species were related. Paleovirology has taken this method one step further to suggest that endogenous retroviruses could serve as an additional indicator of evolutionary relationships. What Darwin would have found most surprising, however, is that despite posing numerous health risks, viruses provide the raw material for selective environmental pressures to act upon.
While endogenous retroviruses have the potential to come back to life and haunt humans, they are also a source of diversity for the human genome. I was fascinated when the article discussed how “persistent viruses actually grow weaker over time” because being lethal to every host they infected would hinder their ability to reproduce. This relationship aligns with the theme of cost and benefit that we’ve seen recurring in biology all year long. Each advantage comes at some sort of a cost, and a recurring characteristic means that it has proven to be advantageous in a particular environment. For example, although humans developed a mechanism that chimps were not able to develop to fight off PtERV, this immunity left us vulnerable to HIV. Furthermore, when tests were conducted on TRIM5, the gene that manufactures a protein that destroys PtERV, scientists found that the protein functioned differently in each primate species — it either protected the organism from HIV or PtERV, but never both.
Given the amount of research that still needs to be done, I think that reviving dead viruses is a valuable and necessary effort to answer many of the questions that remain. While it does raise some ethical concerns, biologists do not take this matter very lightly and recognize the urgency of the issue. With conjectures that “the entire population of Africa will eventually perish” without an effective AIDS vaccine, this has become a public health concern that simply cannot be ignored.