they are identical at the d.n. allyl. unrelated humans? do i have any guesses as to how much an unrelated pair of humans differs at the d.n.a. level. one in what? well it is not very much. one in a thousand. so at the d.n. allyl, the most fundamental unit of our biology, we are 99.9% identical. there is an important message right there. if we compare ourselves to our nearest biological relative the chimp we are 99% identical to the chimp for d.n.a. sequencing we can line up and compare. we are more different from mice and thank goodness if you compare us to broccoli we are mostly different from broccoli at the d.n.a. level. but if you think about it, we have three billion d.n.a. bases even if we are 99.9% identical that means there are three million differences on average between each pair of humans. that is important because that provides a basis for forensic identification. each of us is genetically unique unless we are an identical twin. there are roughly three to four million differences between individuals. that means there are at lea