How viruses evolved – and gave humans a placenta

Essentially, a virus is a package of proteins and genetic information that reproduces in the cells of another organism. Viruses are obligate parasites, meaning that they cannot replicate on their own.

Although it’s debated whether they’re alive or not, they certainly hold genetic information – some of which is similar to ours. But this does not mean that we evolved from viruses.

All life is related to each other to some extent (humans are even somewhat related to mushrooms). However, viruses don’t occupy any branch of the tree of life – there is no single common ancestor virus. Instead, viruses share some genetic information with their host.

As a virus replicates in one of your cells, it occasionally copies bits of your genetic information for itself. These related bits of information then evolve within the virus over millions of years and sometimes give it new abilities.

The opposite process also occurs, albeit rarely, where some of a virus’s genetic information gets taken by our own cells. This may seem like a bad thing, and can be, but it has also given us new abilities.

For example, bits of a virus that were incorporated into our genomes millions of years ago gave us the ability to make the placenta. Without this virus, pregnancy as we know it would be impossible.

So, no, we are not related to viruses in the standard sense. Instead we have a collection of shared interactions with viruses over millions of years. Many of these interactions cause disease, but some have helped make us what we are today

Read more:

• How much do viruses drive evolution?
• Can we make an artificial womb?
• Am I more bacteria than human?
• Why do mitochondria have their own genome?

Looking to read more about viruses? Check out our complete guide to the coronavirus vaccines.

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