Biology

98% of Korean people carry a mutation in the ABCC11 gene that makes body smell nearly undetectable, and 99% have dry, flaky earwax. In contrast, 97% of Europeans and Africans have strong body odor and wet earwax. A single gene variant produces both differences simultaneously.

Mammal milk evolved from skin secretions that originally kept eggs moist. The platypus, the only surviving egg-laying mammal, still coats its soft eggs with secretions to prevent drying, and its hatchlings feed on these secretions for nutrition.

Most birds lack a penis—both sexes mate by pressing a single opening called a "cloaca" together. Ducks are an exception: their corkscrew-shaped penises can reach 42.5 cm, rivaling their body length. Unlike mammals, they achieve erection via lymph fluid in about one second.

In mammal births, a round lump of flesh covered in skin and fur sometimes appears, called 'amorphous globosus.' It is a twin that failed to develop and survives by parasitizing the other's blood. In cattle, it occurs about once in every 3,500 pregnancies.

Submerging your face in cold water triggers the "diving reflex." Heart rate drops 10-25% and blood flow shifts to protect the brain and heart. This ancient mammalian reflex is especially strong in babies under six months.

Menthol makes your mouth feel cool without changing the actual temperature. It raises the activation threshold of cold receptors, making you perceive coldness at temperatures that would not normally trigger it.

Honeybees can understand that zero is smaller than 1, 2, 3, or 4.