Jocelyn Timperley

Sharks have survived all five of Earth’s major mass extinctions and possess a range of unexpectedly advanced traits. They can distinguish patterns, colors and some numerical differences; learn tasks associated with music; form long-term social bonds; and, in some species, develop temporary umbilical scars or exhibit in-utero cannibalism. Their skin is covered with tooth-like denticles that reduce friction, while specialized sensory systems allow them to detect water movement, electrical signals, magnetic fields and possibly a human heartbeat. Fossil evidence indicates that shark ancestors date back roughly 450 million years, making them older than the first trees, dinosaurs, Saturn’s rings and the Pole Star.

Before affordable personal alarm clocks, people relied on daylight, animal sounds, church bells, servants, candles, incense, water clocks and specialized human wake-up callers. During the Industrial Revolution, knocker uppers became essential in British factory towns, waking workers by tapping windows or firing dried peas through tubes; the profession largely disappeared in the 1920s as mechanical alarms became cheaper. Historical sleep patterns were more varied than the idea of a uniformly natural pre-industrial schedule suggests, but researchers note lessons that remain relevant today, including regular sleep times, morning exposure to natural light, reduced evening artificial light and attention to the bedroom environment and pre-sleep habits.

Sharks are presented as ancient, highly evolved predators with surprising capabilities, including mathematical discrimination, musical associative learning, social bonding, and advanced sensory systems that detect vibrations, electric fields, and magnetic orientation. Their biology includes umbilical development, intrauterine cannibalism in some species, and skin composed of denticles that reduce drag. Fossil evidence shows sharks predate trees, dinosaurs, and Saturn’s rings, and their evolutionary history reveals deep divergence from humans despite shared distant ancestry.