https://en.wikipedia.org/wiki/File:Penisstacheln.jpg Day 171 has 18 protein-coding genes (browser view) including the gene AR for the androgen receptor.
A regulatory sequence (an enhancer) near the AR gene is found in most mammals except human (an hCONDEL). The deletion is believed to have caused humans to lack the penile spines found in other mammals.
Click here to see all 8668939 letters of Day 171 with AR underlined.