Photo shows what former rodeo rider Roger Patterson said is the American version of the Abominable Snowman. He said pictures of the creature, estimated at 7 1/2 feet tall, were taken northeast of Eureka, California. Bettmann | Getty Images

Yeti persisted. An Oregon man intent on proving the existence of the mythical creatures known as Bigfoot, Sasquatch, the Abominable Snowman and Yeti in 1976 managed to get the FBI to test hair and tissue samples that he believed might help his case, according to newly released records. "The FBI has analyzed hair in connection with the search for Sasquatch, aka 'Bigfoot,'" an internal FBI memo noted in February 1977. On Wednesday, the same man who spurred that analysis, 93-year-old Peter Byrne, told CNBC that he still hasn't given up hope of proving that Bigfoot is a real — if exceedingly rare — creature. "It's a great challenge," Byrne said, when asked to explain his interest over nine decades in finding creatures widely believed to be figments of imagination, or the inventions of con men. Byrne's web page says that he "has always had an interest in the unknown and the mysterious" since his father used to tell him bedtime stories about the Yeti of the Himalayas. The page says his "first opportunity to go looking for the Yeti occurred in 1946, when he was still in the British Royal Air Force in Bombay, India." A photo on that page shows him "with the famous Yeti scalp" at a temple in the Himalayas in Nepal in 1958. Another photo shows a very big footprint of a possible Bigfoot. His desire to see a Yeti for himself led him to launch three extensive expeditions searching for the Yeti in Nepal in the late 1950s.

Peter Byrne in the Himalya during the searches for the Yeti in 1957. Source: Peter Byrne

Byrne said that in the past 50 years he had found two or three sets of possible Yeti footprints, with five toes on each foot, left in tracks in the Himalayas, at altitudes of 15,000 feet. But he conceded Wednesday that those prints could have been left by Hindu holy men, or sadhus, whom he has seen walking barefoot in the snows at such heights. After moving to the U.S. the 1960s, Byrne went on to direct "The Bigfoot Information Center and Exhibition" in Oregon. With the backing of what he said were wealthy men, he tried to find conclusive evidence of Bigfoot, also known as Sasquatch in America's Pacific Northwest, "I was in it full time, seven days a week," Byrne said of his earlier Bigfoot hunts, which last were funded in the 1990s. "Right now, I'm still active," Byrne said. "We have motion-sensitive cameras out in the mountains" of Oregon, he said. But, he added, "it's a hobby for me now." When told about the FBI documents showing his correspondence with the agency in the 1970s asking it to test hair samples, Byrne chuckled. But he also said, "I don't remember this." Read the FBI's "Bigfoot" File here:

"It's out of my memory," he added, while noting that he does recall asking the FBI in the 1970s about an incident at a campground in Washington state where a Bigfoot was suspected However, FBI records disclosed by the agency on its public documents page show that in 1976, Byrne repeatedly wrote the FBI asking for the tests to be conducted on both hair his group had obtained, and on other samples that he had heard might be in the agency's possession. "We do not often come across hair which we are unable to identify and the hair that we have now, about 15 hairs attached to a tiny piece of skin, is the first that we have obtained in six years which we feel may be of importance," Byrne wrote in a Nov. 24, 1976, letter to FBI Assistant Director Jay Cochran Jr. In an earlier letter, in August of that year, Byrne had asked if hair, "supposedly of a Bigfoot," that he believed had been sent to the FBI by others had been examined. "Will you kindly set the record straight, once and for all, inform us if the FBI has examined hair which might be that of a Bigfoot, when this took place, and if it did take place what the results of the analysis were," he wrote. "Please understand that our research here is serious," Byrne wrote. "That this is a serious question that needs answering." In a response finally sent to Byrne on Dec. 15, 1976, Cochran, of the bureau's scientific and technical services division, noted that the FBI laboratory normally conducts examinations "of physical evidence for law enforcement agencies in connection with criminal investigations." But Cochran added, "occasionally, on a case-by-case basis, in the interest of research and scientific inquiry, we make exceptions to the general policy." "We will examine the hairs and tissue mentioned in your letter," Cochran wrote to Byrne. It was the first time that the FBI apparently tested a sample of hair to see if it was a Bigfoot, according to the records, which contain photocopied images of the hairs. The FBI acted relatively quickly after Cochran told Byrne the tests would be done.

14-1/2 inch Bigfoot footprint found by Peter Byrne's Bigfoot research team in the Six Rivers National Forest in Northern California in 1961. Source: Peter Byrne