For some the "Bigfoot skull" was reminiscent of the famous Piltdown Man find, a huge skull found around 1908 in Sussex, England, that seemed to be evidence of a previously unknown humanlike animal. It was later determined to be a hoax. In his book "Encyclopedia of Dubious Archaeology: From Atlantis to Walam Olum," anthropology professor Kenneth Feder calls it "almost certainly the most significant fraud in the history of paleoanthropology. It was successful, in the dual sense of generating so much support and being so long lived, because it precisely fulfilled a preferred vision of human evolution."
As Feder explains, the Pildown forgery was revealed only a few decades after Darwin's "On the Origin of Species" was published, and "scientists in the late nineteenth century expected the first human ancestor to be, essentially, an ape with an oversized head." Whoever engineered the hoax-the culprit remains unknown though the handful of suspects includes Sir Arthur Conan Doyle, creator of Sherlock Holmes-was aware of this and created the fake (using human skull fragments and an orangutan jawbone) to fool scientists.
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Thus when many people of the time looked at the Piltdown Man skull, they saw what they wanted to see and interpreted it as they wanted to interpret it. This is in what psychology is called "confirmation bias." It's the very human tendency to interpret information (and especially ambiguous information) in ways that support our pre-existing ideas and beliefs.
In the case of the Utah rock, Todd May clearly believes in the existence of Bigfoot (having seen the elusive creature twice, though apparently without a camera handy either time). It's likely that many other people had noticed the same rock but thought nothing of it (other than that it looked vaguely like a head), because they didn't have the psychological bias that May did toward seeing Bigfoot.
Another example occurred in 2010 when a woman diving off the coast of Aruba photographed a vaguely human-shaped form which she believed might be a skeleton. It was later determined to be a rock formation, but the interesting psychological question is why she would have thought it was a skeleton in the first place, instead of rock or coral common in the area. The answer is that Aruba was at the time the center of one of the best-known missing persons cases in the Caribbean, if not the entire world. That's where a young woman named Natalee Holloway went missing in 2005, and visitors to the island had been asked to look for any sign of the woman-dead or alive.
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Unlike the Piltdown skull, there is no indication that the Bigfoot rock is faked or hoaxed in any way; it's just a rock that happens to look (kind of) like a huge head. In fact people often see faces and heads where they don't exist: It's a phenomenon called pareidolia, in which the brain sees faces in ambiguous stimuli such as clouds, coffee stains, and rocks.
Though news stories and social media have presented the find as recent, the Bigfoot rock was actually found in June 2013. Sharon Hill, a geologist and former editor of the website "Doubtful News," explained to Seeker in an e-mail why the story is in the news again: "I'm thinking this was a result of it being a 'throwback Thursday' link that got picked up by some content seekers at other outlets. Over the past decade, there has certainly been a shift to producing lots of content that sounds sensational over researched news articles. The Internet-connected public now has access to news feeds of all kinds, at all times and everywhere. Media outlets have to feed this beast and they do it by recycling and copying a lot of content that hardly qualifies as 'news.'"
In the end, Hill notes, "A guy who finds an interesting-shaped rock is hardly news [but] certain buzzwords are used to grab attention and make a non-story into a clickable opportunity... people can't resist checking it out, even if just to laugh and feel superior. Humans are wired to be curious about the weird and seemingly mysterious." Ultimately the story of the "Bigfoot skull" tells us nothing about the mysterious manlike monster said to roam North America, but much about psychology and social media.