Venomous animals have been admired and feared since prehistoric times, and their venoms have been used to both benefit and impair human health. In 326 BCE, Alexander the Great encountered lethal arrowheads in India that, based on the symptoms of dying soldiers, were most likely laced with venom from the deadly Russell's viper. By contrast, snake venom has been used in Ayurvedic medicine since the 7th century BCE to prolong life and treat arthritis and gastrointestinal ailments, while tarantulas are used in the traditional medicine of indigenous populations of Mexico and Central and South America. The modern era of venom research has so far yielded six venom-derived drugs. Recent work has elucidated the evolutionary biology of venoms and provided an impressive diversity of new therapeutic drug candidates.