Question

I was just reading Evolution of lactose tolerance, and in it oneline says "But there was a time in human history when our diet andenvironment conspired to create conditions that mimicked those of adisease epidemic".

Something I've always wondered is rather than natural selectionoccurring and survival of the fittest and so on, is that a viralepidemic caused a mutation in the survivors, i.e. DNA was insertedfrom the virus that modified the survivors genome. There is someevidence that a significant percentage of the human genome comesfrom viruses. Probably a naive question - so is there any evidencethat this has occurred? From my lay perspective this is whatattempts at genetic engineering use, so it's possible naturealready did this?

It's always seemed to me that natural selection and pointmutations, and the chance meeting of two people with the samemutation would be too slow and viruses would be a more efficientmethod to evolve a large population at the same time. Things likepunctuated evolution might support this? not really sure.