In his Journal of Researches as well as the condensed recount found in The Voyage of the Beagle, a young Charles Darwin describes his considerable astonishment

In his Journal of Researches as well as the condensed recount found in The Voyage of the Beagle, a young Charles Darwin describes his considerable astonishment at the constitutional robustness of the indigenous peoples he encountered in Tierra del Fuego in the 1830s. At that time they were called Fuegians, though in more modern times they are referred to as Yaghans. Despite their homelands being situated among the harshest, most inhospitable climes on Earth, with year round temperatures frequently near or below freezing and constant powerful circumpolar winds from the 'furious fifties,' they were able to tolerate such extreme conditions despite their traditional attire consisting of little more than a loincloth and an occasional loosely draped shawl. They frequently went without protection on their upper body and lower extremities altogether. Darwin describes a vivid scene where a Fuegian mother is standing in a shallow boat that approaches the Beagle in order to conduct raid. She's wearing nothing but newborn nursing at her breast, and she and her child both seem indifferent to the the snowfall and freezing rain melting on their skin. They did not use permanent dwellings, and basically lived as gatherers using simple temporary makeshift huts with one side facing the wind and the other side open, and of course a fire, which gave the region its name. But it was not uncommon for them to spend days foraging for mussels, drenched in the frigid crashing breakers of the Southern Ocean. This is 30 years before he published the Origin of Species and long before he had developed an articulated concept of natural selection, but The experience did inspire him to remark how it made intuitive sense that as the population of mankind spread across the Earth, that it would have differentiated and adapted to different climates in accordance with whatever underlying principles had driven the same process he had observed this happening with other species. If curious, Google around for Jemmy Button and York Minster, these being too individuals who had been kidnapped from Tierra del Fuego and taken to England on a prior Beagle expedition, and returned on the one accompanied by Darwin.