The human gene ABCC11 determines whether your sweat smells bad or not. It also determines whether your earwax is wet or dry.
ABCC11 is a gene in one of the oldest gene families on the planet. That family, the ABC transporters, are responsible for moving stuff around the body at a cellular level: amino acids, peptides (made of amino acids), and so on. The gene family so old that everything alive today has ABC transporters somewhere in its genetic setup. But the variation in ABCC11 in humans also answers one rather specific question: does your sweat stink?
There are two alleles (variants) of ABCC11. If you get the dominant gene expression, your body odour is very smelly. You sweat a lot, and the sweat produced under your arms and elsewhere is a great breeding ground for various types of Staphylococcus bacteria. This all contributes to the characteristic stink. If you get the recessive gene expression, though, the situation is completely different. You sweat less, and when you do sweat it does not produce the same bacteria-breeding melange. To put it another way, with the right allele, your sweat simply smells better.
In addition to being the sweat gene, ABCC11 also determines what your ear wax looks like: thick and gloopy, or dry and flaky. If you have dry ear wax you can scoop it out of your ear with a special spoon; if you have the gloopy kind, you cannot.
The recessive variant of this gene is more common in people from East and Northeast Asia. Scientists hypothesize that it’s the result of a mutation a few millennia ago that spread around the region but not beyond it (at least until global migration became a thing).