The Writer's Almanac with Garrison Keillor

Thor Heyerdahl's 4,300-mile journey across the Pacific Ocean ended on this date in 1947. His balsa-wood raft, the Kon-Tiki, smashed into a reef in French Polynesia.

Heyerdahl had been trained as a zoologist, but had developed a strong interest in cultural anthropology. He and his bride spent their honeymoon living primitively on the island of Fatu Hiva, in the Marquesas Islands. They studied the local plant and animal life for a year. Heyerdahl served as a parachutist during World War II and never really stopped thinking about Polynesia. He came up with the theory that the islands had been populated by people from Peru, coming from east to west on the ocean currents, much as the flora and fauna had done. Scientists believed that the Polynesian people had originated in South Asia, and they scoffed at the idea that it was even possible for pre-Columbians to cross the Pacific Ocean with materials available to them at that time. Heyerdahl couldn't get any publishers or researchers to take his theory seriously, so he decided he would prove it by an actual demonstration instead.

Heyerdahl convinced five of his friends to join him on a daring expedition to test his theory. Besides Heyerdahl, the crew consisted of a navigator and artist; a steward; two radio experts; and an engineer who specialized in technical measurements. Funded by private loans, they built a 40-foot raft of balsa logs lashed together with hemp ropes, with gaps between the logs for the water to drain out. The cabin was built of bamboo and had a thatched roof of banana leaves. The mast was made of planks of mangrove, and it held a square sail. No metal was used in the raft's construction. It was a replica of the type of raft that native Peruvians would have used in the early 1500s, based on reports by Spanish conquistadores, and Heyerdahl named it Kon-Tiki after an Incan sun god who walked across the Pacific. Heyerdahl and his crew did carry some modern technology, like a radio, navigational equipment, and watches, as well as emergency survival equipment. They also brought coconuts, sweet potatoes, gourds, and some tinned army rations, which they supplemented with fish they caught along the way.

In 101 days, the raft traveled 4,300 nautical miles, weathered two major storms, and made it all the way to the coral island of Raroia, near Tahiti, proving that Peruvian Incans could have made the voyage themselves. Heyerdahl wrote a book about the adventure: The Kon-Tiki Expedition: By Raft Across the South Seas (1948), and made an Oscar-winning documentary film of the same name. Heyerdahl was a gifted storyteller, and his story was hugely popular with the public, but scientists were unconvinced. They believed that Polynesian language and culture point to Asian, not American, origins. One critic wrote, "It is unfortunate that he has allowed his obsession with a South American connection to overshadow the far more interesting and important subjects of the islanders' cultural history, way of life, and destruction of their environment."

Heyerdahl was never discouraged, and he used the royalties from the book to fund further expeditions: to the Galapagos Islands, to Easter Island, and across the Atlantic and Indian Oceans. He sailed a reed boat from Egypt to Barbados in 57 days in an attempt to prove that South American pyramids were inspired by their Egyptian counterparts. He was well into his 60s when he retired, saying that there were no other oceans to cope with and no more early boat designs that hadn't already been tested. He said: "I have challenged a lot of old dogma, and this has stimulated a lot of discussion. And in science you need discussion."

In 2011, nine years after Heyerdahl's death, Norwegian scientist Erik Thorsby presented evidence that shows a small amount of South American DNA in the genetic make-up of Easter Islanders, which lends some scientific support to Heyerdahl's theory, even if it doesn't fully vindicate him. "Heyerdahl was wrong," Thorsby said, "but not completely."

The Battle for Guadalcanal began on this day in 1942, in the Solomon Islands in the South Pacific. Japanese troops had started building an airstrip there the month before, and on August 7, in the Allies' first major offensive in the Pacific, 6,000 U.S. Marines landed and seized the airfield. Both sides then began pouring in reinforcements, with bitter fighting in the jungle. By January 1943, six separate naval battles were fought near Guadalcanal as both sides tried to land more men. The Japanese finally evacuated the island in February 1943.

It's the birthday of anthropologist and archeologist Louis Leakey, born in Kabete, Kenya (1903). His parents were Anglican missionaries to Africa, and he lived in Kenya until he was 16. He studied anthropology at Cambridge at a time when most anthropologists believed that human beings had originated in Asia. But Leakey had read Darwin's theory that human beings might have originated in Africa, because Africa is the home of our closest relatives, chimpanzees and gorillas. As soon as he graduated from Cambridge, he moved back to Africa to prove Darwin right.

In 1948, Leakey and his wife found one of the earliest fossil ape skulls ever discovered; it was between 25 and 40 million years old. It is now believed to be the skull of the ancestor of all large primates, including humans. Then, in 1959, they turned up another hominid skull, which was 1.75 million years old. It was the oldest skull of a close human relative ever found at that point, and it helped persuade other anthropologists that Africa was indeed the place where human beings had evolved.

Today is the birthday of author and editor Anne Fadiman (books by this author), born in New York City (1953). Her father was the critic and essayist Clifton Fadiman, and she grew up in a literary household, making castles out of the books in her father's library. She was working as a reporter when she got an assignment to write for The New Yorker about a young Hmong girl with epilepsy and her parents' difficulty dealing with the American medical system. The New Yorker decided not to print the article, so Fadiman turned it into her first book, The Spirit Catches You and You Fall Down (1997). It took her eight years to finish the book.

She's also written two collections of essays. Ex Libris: Confessions of a Common Reader (1998) is about her deep love of books. She believes that if you truly love a book, you should sleep with it, write in it, read aloud from it, and fill its pages with muffin crumbs. And in her other collection, At Large and At Small: Familiar Essays (2007), she writes about her many obsessions, from her childhood butterfly collection, to the lost art of letter writing, to English essayist Charles Lamb.

On this day in 1934, the U.S. Court of Appeals ruled that the novel Ulysses, by James Joyce (books by this author), was not obscene. It had been banned in the United States in 1920, and though it was a big-seller on the black market, and Joyce knew he was losing a lot of money to pirate publishers, the only way to fight the ban was to provoke the government into a new obscenity trial. So in 1933, Random House decided to import a single version of the French edition of Ulysses, and the company had people waiting at the New York docks for the book's arrival. It was a hot day and the U.S. Customs inspector didn't want to be bothered with another inspection, but the Random House people made sure that one book was seized. Random House and Joyce appealed, and the judge, John Woolsey, ruled that it was not pornographic. In his judicial opinion, Judge Woolsey wrote, "In respect of the recurrent emergence of the theme of sex in the minds of his characters, it must always be remembered that his locale was Celtic and his season Spring."