More Virus Than Human

In popular culture, scientific inventions seem to get all the hype, but scientific discoveries are arguably far more edge-of-your-seat. Discovering a phenomenon that makes the world work, that occurs in real-time, and explains how we came to be, beats out any flying car. But if you need science to be as thrilling as Jurassic Park, look no further than paleovirology.

Paleovirology explores how viruses have evolved through history and how they have evolved in us. Yes, a certain type of virus has been incorporating itself into our genome for millennia. These endogenous retroviruses have the ability to convert RNA into DNA, defying the order scientists have long considered the central dogma. When these retroviruses invade our germ cells, the egg and sperm, they can be passed down as part of our genes. The human genome is, in fact, only 2% human and 8% viral!

Viruses are driving the speed of our evolution by forcing us to adapt and change to evolve against them. They are also responsible for some thing we consider uniquely human, the placenta. The placenta has been found to have an endogenous retrovirus in the outer layer that connects the fetus and the mom. This type of retroviruses is used to latch on to cells they infect, so the human babies act like parasitic retroviruses.

This is crazy mind-blowing by sheer intrigue, but it’s practical uses are also very interesting. Paleovirology is currently trying to resurrect some of these endogenous viruses in order to study current viruses like HIV, which may also be endogenous. Chimps do not become sick when exposed to HIV and one of the most striking differences between the human genome and the chimp genome, is a certain endogenous retrovirus called Pterv. Humans have adapted a gene Trim5A to defend ourselves against Pterv but it made us susceptible to HIV. Some scientists hypothesize that we can trace the split in evolutionary paths between humans and chimps to around the same time a this virus was active. And, not only that, but we may be able to predict future spits in the same way.
All the hows and whys, we are not yet sure, and that is the exciting part. On the timescale of evolution and in the short blip that is human time, humans have faced near extinction from several viruses and the humans that survived managed to incorporate the viral DNA into their genome. Part of the reason we were able to incorporate them harmlessly is because over the course of evolution, the virus collected mutations. One genius paleovirology is trying to apply this ideas to combat AIDs by speeding-up the evolution of AIDS until it mutates to inactivity. This logic would seem totally, counter-intuitive and certainly Jurassic Park-scary but it may offer us the most innovative way to combat a horrible disease, and that is exciting.

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