Day 46 has only 18 protein-coding genes (browser view). One encodes lactase, which lets baby mammals digest their mothers’ milk. In most people, the lactase gene is turned off after childhood, which means they are lactose intolerant. Lactase persistence, allowing adults to drink milk, recently evolved. In Europe, this change in the control of the lactase gene was the result of a single nucleotide change upstream of the gene, rs4988235.
Click here to see nucleotide view of Day 46, with the rs4988235 SNP flashing.