dean hamer: dna is like a blueprint that determines not t only our physical bodie, but also, at least in part, our brains. and our brains, of course, are what control our behavior, and so, although it surprises some people, our genes also play a role in the way we think about things, the way we feel about things, and the things that we do. so we have 100,000 genes, and all of us have to have two copies of each gene, one from each parent. each time they're being transmitted from parent to offspring, the genes have to be copied. and the copying system isn't perfect, so little mistakes are made, or changes, and most of them are irrelevant. but over time, we have in the population for any given gene, variance. in fact, my dna, and your dna, and somebody else's dna is 99.9% the same. but there's about one base out of 1000 that's different. so michael jackson's dna might read "a," and michael jordan's dna might read "g," and michelangelo's dna might read "c," and so on and so forth. and surprisingly those very few differences, that one out of 1000, is enough to make all the differences in t