Three percent may sound small, but it is actually a statistically large portion of the human genome. Though the sense of smell as a whole is complicated due to the sheer number of odors a human can identify, Buck and Axel’s assumptions were able to cut through the noise and find incredible results. Shubin does not explain how the genes for smell in mice were already known, but it is worth noting that the entire mouse genome has been sequenced, so isolating the genes for smell would be as simple as comparing a “normal” mouse genome to the genome of a mouse who had a dysfunctional sense of smell.