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

Something I've always wondered is rather than natural selection occurring and survival of the fittest and so on, is that a viral epidemic caused a mutation in the survivors, i.e. DNA was inserted from the virus that modified the survivors genome. There is some evidence that a significant percentage of the human genome comes from viruses. Probably a naive question - so is there any evidence that this has occurred? From my lay perspective this is what attempts at genetic engineering use, so it's possible nature already did this?

It's always seemed to me that natural selection and point mutations, and the chance meeting of two people with the same mutation would be too slow and viruses would be a more efficient method to evolve a large population at the same time. Things like punctuated evolution might support this? not really sure.

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Why would two people with the same mutation have to meet unless the allele was recessive? –  Rory M Oct 29 '12 at 16:34
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There is plenty of evidence of integrated viral genomes (eg, retroviral genomes) within the human genome. I don't think we currently understand the role the left over genetic material plays in human evolution, but we are certainly "stamped" with viral interactions. –  leonardo Oct 29 '12 at 19:53

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There is some nice work from Pardis Sabeti in this broad area (not just viruses but pathogens in general). Her colleagues have found polymorphisms in SLC40A1, encoding an iron transport protein, that influence susceptibility to tuberculosis. She's also looked at human genetic variation and susceptibility to Lassa fever. And this paper talks about CD36 and malaria in sub-Saharan African populations (no association). Look at her work from 2009 onward, as there is a lot there. They're also looking at variation in the pathogen because it is a two-way interaction.

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The simplest example, that I can recall are the flu pandemics. The 1918 pandemic is the first to be described because of its severity, but quite possibly not the first in human history (see for example the Black Death - Yersinia pestis is a bacterium, but in the 15th century in just a few years it covered almost all of Europe, sometimes killing up to 40% of population in a given area).

Influenza pandemics appeared quite regularly during the 20th century, usually every 20 years and killed suspiciously many people compared to yearly influenza strains. Additionally, a person who survived one pandemic, was unaffected or only mildly affected by the next pandemic.

All this suggests, that the pandemics "clear" the population from susceptible individuals, and regularity of pandemics (notice, that 20 years is more or less the time of one human generation!) assures that the new generations also go through this kind of selection. The surviving individuals are more resistant to all strains of influenza then those, who never suffered from a pandemic. Maybe the influenza didn't mutate our DNA, but it could be a major force of natural selection.

And one more note: did you notice the great noise in media every time a new potentially pandemic strain is discovered? Actually, it's not just hyperboly of the danger. Last pandemic was in the '70s, so it's high time for a new one. And, since the last one was almost 40 years ago, the new one (when it happens) will probably be very severe.

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indeed, but the selection there is can this virus/bacteria kill me. You could argue that certain personality traits/intelligence etc was a byproduct of this - e.g. a fear of rats from the plague, and perhaps an intelligent person would be more inclined to notice patterns and adjust their behaviour to avoid infection. I was wondering if there was a more direct result - fragments of dna inserted into genomes that altered organisms, certainly possible I'd imagine - was wondering if it ever actually happened - that anyone knows about anyway. –  daven11 Oct 29 '12 at 13:11
    
I think it did, but right now this is just a vague memory of an Evolutionary Genetics lecture. I'll find more time tomorrow, and try to locate my notes and the actual data. –  jkadlubowska Oct 29 '12 at 18:05

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