What does the article suggest about the role viruses have played in evolution? What do you think? Has this changed your view/understanding of viruses?
Viruses have helped shape the evolution of species by acting as a selective pressure. While endogenous retroviruses have inserted their DNA into human DNA, little have yet to be discovered about their direct impact (this DNA is part of what is considered “junk” DNA). There are a few notable exceptions, such as the development of the placenta in mammals, or protection against similar viruses. But the more important role these viruses have played is by acting as another way to influence natural selection. By examining the pieces of viral DNA scientists can determine what viruses early human ancestors were vulnerable to. These early infections then help researchers understand what viruses modern day humans are susceptible to and why. Early ancestors developed defenses against certain viruses; the virus would then mutate, and in response the population would have to adapt. The resulting adaptations protected against a certain virus, but not another (as in the example with PtERV and HIV).
The relationship between the evolution of viruses and humans reminded me of the idea of coevolution. I was not too surprised by the connection, but the resulting impacts on modern humans fascinated me. I did not know that a possible reason for having a placenta came originally from viruses, or that we may have “borrowed” a method from a virus and used it to our advantage. It was also interesting that certain early infections caused modern humans to lose immunity from viruses that infect us today. I did not consider that immunity from one virus may come at the cost of vulnerability to another. It seems like you just can’t win.
Viruses are more complex than what I had first thought. I always thought they were cool–they were these non-living things that ruthlessly pursued their targets until nothing was left. But after reading the article, I now see there is more to them than just the “determined killer.” While I would not say that viruses are here to help move human evolution along, I can appreciate their power to influence its direction.