Flip it around as well. Take for example Zika. When passed from mother to unborn it can cause various brain abnormalities. But perhaps eons ago a virus is what made homo sapiens more intelligent. If a virus can mangle the brain it can also nudge it in a positive direction.

Finally, human DNA is peppered with traces of viruses.

https://www.smithsonianmag.com/science-nature/virus-genes-hu...