In the mid-1960s, a well-preserved hominin fossil is discovered in the Moroccan desert. Examination of the fossil, known as Fat Man, shows it to be around 550,000 years old. Decades later, DNA and protein analyses of the Fat Man skull in the OMICS National Laboratory in the U.S.A. reveal proteins of unknown function. The proteins are classified as olfactory receptors but distinctly different from known receptors. Why did humans 550,000 years ago have these receptors, and what were they used for?