Wait: this looks like a science post, but it is really history! Very long-time ago history, like 160 million years ago. But, due to the science of evolutionary genetics, we know this very old story is of immediate relevance to every human, as well as to a very special virus that made our lives possible.
Our genome contains about 3 billion base pairs of DNA, built up over the eons to contribute to what we are, and some of that DNA (maybe 4%, still debated) are actually ancient copies of viruses. These special viruses (called “endogenous retroviruses) have managed to insert themselves into our DNA to get passed along through sexual reproduction. This is a very back-door way for viruses to reproduce, but it has led to some amazing symbiotic developments in evolutionary history.
Like placentas, for instance. It turns out that the gene called “synctin” is reponsible for forming part of the placenta that shapes the boundary between maternal and fetal tissue, and synctin comes from one of these retroviruses. As science writer Carrie Arnold states, “these snippets of DNA are helping to blur the boundaries between human and virus.” This mind-blowing fact drives home a realization that the line separating humanity from our environment is artifical.
Source(s): Carrie Arnold, _NOVA_, “The viruses that make us human,” Wednesday Sept 28, 2016. (@pbs.org/wgbh/nova/article/endogenous-retroviruses/). Image getty images plus. Also see “virology lectures 2020 #9, reverse transcription and integration,” Columbia University, Professor Vincent Racaniello.
