Why do humans have hair almost everywhere… except our palms, soles, and mysteriously bare elbows? In this episode of Explain It Like I’m 5, Alex unpacks the weird and wonderful world of human hair—what it is, why we still have it, and why it grows in some places and not others. We explore how each strand of hair grows from a hair follicle, how keratinforms the dead hair shaft we see, and why humans are actually “mostly hairless” compared to other mammals, even though we still have about 5 million hair follicles.

Alex explains the functions of hair: protection (eyelashes, eyebrows, nose hair), temperature control, touch sensitivity, and social signaling in attraction and communication. We dive into why we have thick scalp hair, fuzz on arms and legs, hair in armpits and the groin—but smooth palms, soles, and low-hair areas like elbows and knees, where hair would interfere with grip, walking, or constant bending. The episode also covers why human head hair grows so long, how hair growth cycles work (anagen, catagen, telogen), and why shaving doesn’t actually make hair grow back thicker.

Along the way, you’ll hear fun hair facts—from record-breaking long hair and “werewolf syndrome” (hypertrichosis) to ancient wig culture and how evolution may have favored less body fur for sweating, parasite control, and social signaling. Alex also touches on hair loss, culture and identity, and why your elbows aren’t truly bald—they’re just rocking very fine, almost invisible hair. By the end, hair goes from a daily annoyance to a fascinating story of biology, evolution, and self-expression growing right out of your skin.