Despite the absence of advanced microscopy or knowledge of DNA, Darwin outlined a mechanism that species utilize to modify into more capable organisms. His discovery paved the way for further inquiry, and eventually, a newfound understanding of both our historical past and our modern day existence. The Origin of Species created a foundation for evolutionary biology, yet, even today, new discoveries challenge and reaffirm the ideas presented. Darwin’s Surprise outlines how the presence of viruses assisted the development of life on earth and also acted as a constant threat to its existence.
Viruses are one of the only outliers to Darwin’s model of descent with modification. For Darwin, all changes in a community were random mutations that coincidentally were advantageous. The presence of viral DNA in cells is not a random mutation, it’s a completely new segment of DNA inserted permanently into a species blueprint. Granted whether the new DNA helps or harbors the life processes in the organism is dependent on the environment (like Darwin predicted) the idea that our DNA is littered with “junk” DNA changes how we perceive evolution.
We assumed, like Darwin, that once a trait was surpassed by a better modification, it gradually dies out. The fact that our genome maintains viral DNA segments, says that just because a trait is phenotypically dead doesn’t mean that will be reflected by our genetic code. Though we can’t blame Darwin for not recognizing this fact, especially since his work was limited by the lack of a microscope. Since he only could study the features he observed, it makes sense that problematic adaptations would end with the organism. The continuation of junk DNA plays out well for scientist though, especially because DNA sequencing can look at patterns in viral DNA to find evolutionary links.
The idea that viruses are integrated into our DNA and now some play a role in our survival, seems contradictory to everything a virus is. The sole purpose of a virus is to inject DNA into a host cell and replicate, often times leading to distress. Except, some viruses don’t harm people. Instead, without their presence, what we perceive as human now would be very different. For instance, the protein syncytin utilizes the same mechanisms as retroviruses to fuse placental cells together. Thierry Heidmann and other virologist argue that without viruses the placenta would not exist. It’s hard to imagine how our species would differ based on one small change in our historical environment.