You find a sheet of paper in a pile on your desk. The pile is a set of papers for a friend of yours you do some "pro bono" work for. He's your average 30 yr old single male with no animals and--as far as you know--nothing really going on in his life.

Most of it is pretty normal, stuff like food and gas. (Known Normal Human DNA)

But there's also some atypical instances, like "Victoria's Secret", various shoe stores, and a couple runs to Petsmart. There's also a strange charge from a local OB/GYN office and a donation to PETA and a breast cancer research fund. ((Differences from Known Human DNA))

You recently spoke to your friend and they made no mention of any of these and no mention that their card/account information was missing. ((The Human Genome has not notably changed recently and has no indication of recent unstudied change))

Which do you think is more likely?
1) Your friend is making strange purchases? (Variation in Human Genome)
2) One of your other client's papers ended up in his stack of papers (Genome is not Human)


Let's take this a step further. Let's assume you're a sexist bastard who refuses to do any accounting work for women--and always have--despite the fact that your office works for a Femi-Nazi Coalition ((You're unfamiliar with those combinations of DNA variations))

Which do you think is more likely?

1) This one of your other clients? ((This is another Homo-species you're familiar with))

2) One of your coworker's papers ended up on your desk. ((This is a Homo-species you have not encountered before))


I hope I put that into terms that make more sense to you? There are probably holes in my metaphor, but please try to ignore them for my greater point