YouTube A supposed sighting of “Bigfoot,” as broadcast over YouTube

In November 1976 Peter Byrne, the director of a group called the Bigfoot Information Center, wrote a letter to the FBI. His request? Byrne wanted the agency to analyze some hairs which he suspected might belong to Bigfoot, the hairy, ape-like figure of folklore.

A month later, the FBI wrote back to Peter Byrne. The agency admitted that Byrne’s request was unusual but said that it was willing to make an exception to their usual practices. The FBI agreed to examine the hairs to see whether they really belonged to Bigfoot…in the interest of “research and scientific inquiry.” The agency wrote,

“The FBI Laboratory conducts experiments primarily of physical evidence for law enforcement agencies in connection with criminal investigations. Occasionally, on a case-by-case basis, in the interest of research and scientific inquiry, we make exceptions to this general policy. With this understanding, we will examine the hairs and tissue mentioned in your letter.”

The letters and accompanying analysis were sealed in the FBI’s vault until this week, when they were released under the Freedom of Information Act. You can see the FBI’s file on Bigfoot here.

Spoiler Alert: the Mysterious Hairs Came from a Deer, not from Bigfoot

The FBI sent the mystery hairs to its lab, which carried out an in-depth analysis. By February of 1977, the FBI had an answer: the hairs in question did not belong to Sasquatch. They were, in fact, from a deer. Here’s what the agency wrote:

“The hairs which you recently delivered to the FBI laboratory on behalf of The Bigfoot Information Center and Exhibition have been examined by transmitted and incident light microscopy. The examination included a study of morphological characteristics such as root structure, modullary structure, and cuticle thickness in addition to scale casts. Also, the hairs were compared directly with hairs of known origin under a comparison microscope.”

The conclusion, after the in-depth examination? Here it is. “It was concluded as a result of those examinations that the hairs are of deer family origin.”

The FBI Said This Was the First Time They’d Analyzed a Possible Bigfoot Hair

The FBI’s Bigfoot file shows that the Bigfoot Information Center first wrote to the agency as early as August 1976. Peter Byrne, the director of the Bigfoot Information Center, wrote to the FBI because, he said, he’d heard that the agency had already carried out a few investigations into possible Bigfoot hairs. Byrne said he wanted to know, for once and for all, whether that was true.

The FBI wrote back to say that no, they’d never analyzed a potential Bigfoot hair before. A few back-and-forths followed, with Byrne pushing for details. The FBI responded that they had often been asked to analyze hairs to see whether they belonged to Bigfoot — but the agency said it had never complied with those requests. The FBI said that any reports that they had, in fact, investigated Bigfoot in the past were false.

The FBI’s Bigfoot file includes two photographs of the “Bigfoot” hairs sent in by the Bigfoot Information Center (the hairs, which were submitted to rigorous analysis in the FBI lab, turned out to belong to the deer family). The file also includes a statement that by agreeing to analyze the hairs, the FBI was not in any way changing its policy on Bigfoot or on its willingness to analyze objects sent in by members of the public.