October 6 is the birthdate of Thor Heyerdahl (1914 - 2002).  His insights, analysis and expeditions provided some of the most important evidence for what is often called the "diffusionist" theory versus the "isolationist" theory.  

The diffusionist theory argues that ancient peoples had the capability of deliberately and repeatedly crossing the oceans, including the Atlantic and the Pacific, and that they did so as far back as the time of the ancient Egyptians.  It thus stands agains the isolationist theories taught by most conventional academicians today, which categorically rejects any suggestion of the possibility of cultural contact between peoples from different continents in ancient times, despite abundant evidence around the world that seems to suggest such ancient contact.  

Thor Heyerdahl entered into this momentous question by several happy circumstances beginning in his early life, which -- when brought into contact with his boundless curiosity and irrepressible optimism and adventurous spirit -- led to several famous adventures and discoveries of tremendous significance.  

This webpage from the Kon-Tiki museum explains that as a young student at the University of Oslo, Thor Heyerdahl met Bjarne Kroepelien, who had traveled to the South Pacific, a part of the world that had fascinated Heyerdahl since childhood.  Kroepelien assisted the young Thor Heyerdahl when Thor and his new bride Liv decided to try to live on an undeveloped island (Fatu Hiva) in the Marquesas to study the local flora and try to determine the route that had brought the various species to the island.  

It was Kroepelien's letter to the Tahitian Chief Teriieroo which enabled Thor and Liv to spend a month with Teriieroo on Tahiti, for practical training in the traditional methods of living off the land.  They stayed a year but insect-borne disease forced them to seek medical attention on neighboring Hiva Oa.  There, another Norwegian who had permanently settled there on a coconut plantation showed Heyerdahl some stone statues in the jungle, which -- along with his friend's suggestion that similar statues could be seen in Colombia, in South America -- fired Thor Heyerdahl's imagination and started him on the pursuit of theories that went against the settled opinion of the historians and anthropologists of his day, and launched him on the many adventures and investigations that would become his life's work.

Heyerdahl became convinced that the islands of the Pacific had been peopled originally by people from South America, perhaps a people who were the predecessors of the Inca, who had traveled eastward on balsa rafts, and who were later joined by another wave of people from the northwest tribes of North America, who had traveled southeast on double-hulled canoes.  These two peoples later mixed (sometimes peacefully and sometimes violently) on the various islands of the wide Pacific, leaving a distinctive Polynesian culture that stretched all the way from Easter Island (Rapa Nui) to New Zealand (Aotearoa).  

Meeting solid opposition from those who said this theory was impossible, Heyerdahl in 1947 undertook his most famous adventure, the Kon-Tiki expedition, to prove that long-distance travel over the open ocean in balsa rafts was not only possible, but extremely practical.  In his best-selling account of that expedition (still thrilling reading today), he explains the origin of the expedition's now-famous name:
Virakocha is an Inca (Ketchua) name and consequently of fairly recent date.  The original name of the sun-god Virakocha, which seems to have been more used in Peru in old times, was Kon-Tiki or Illa-Tiki, which means Sun-Tiki or Fire-Tiki.  Kon-Tiki was high priest and sun-king of the Incas' legendary 'white men' who had left the enormous ruins on the shores of Lake Titicaca.  The legend runs that the mysterious white men with beards were attacked by a chief named Cari who came from the Coquimbo Valley.  In a battle on an island in Lake Titicaca the fair race was massacred, but Kon-Tiki himself and his closest companions escaped and later came down to the Pacific coast, whence they finally disappeared oversea to the westward. . .  18-19.  
Heyerdahl explains that the existence of strong traditions as far away as the Marquesas of a founding anscestor named Tiki, who had come to the islands "from a mountainous land in the east which was scorched by the sun" (18).  Hence, his voyage and the vessel he and his companions used in order to prove such a direction of travel was possible, even over the vast distances and mighty ocean swells of the broad Pacific, was dubbed the Kon-Tiki.

Later in his life, Heyerdahl undertook similar voyages across the world's largest oceans in ships built of traditional materials and design, including the Ra voyage across the Atlantic and the Tigris voyage across the Indian Ocean.

For previous posts referring to some of Thor Heyerdahl's arguments against the isolationist theories, see also:
For a partial list of some of the overwhelming pile of evidence which supports the "diffusionist" theories and casts serious doubt on the "isolationist" theories, see the links in this previous post entitled "The Calixtlahuaca head."

Also, while October 6 is an important date because of the birthday of Thor Heyerdahl, October 5 (still the date here in California as this is published) is even more important, as it is the birthday of my father -- Happy Birthday!  He taught me to make Norwegian crepes, which I had for breakfast this morning.  He also introduced me to the love of looking at the stars, beginning with the wonderful book Find the Constellations, by H.A. Rey -- and plenty of trips outside together to look up at the night sky and try to find the constellations ourselves.