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The ‘Humanzee’ conspiracy: The wild history, oddities behind Orange Park’s old ‘monkey farm’ mystery

1930s monkey lab in Orange Park remains shrouded in mystery

CLAY COUNTY, Fla. – More than anything else in Northeast Florida’s history, the old monkey research lab in Orange Park has sparked wild speculation.

Closed in the 1960s, the lab remains the focus of conspiracy theories and unanswered questions about what went on behind its secretive doors.

News4JAX dug into the mysterious history of the old monkey farm/lab, uncovering details that sound straight out of a science fiction movie.

Yale (Yerkes) Primate Research Laboratory

It all started in the 1930s in Orange Park, where a facility operated under the name Yale Primate Research Laboratory before being renamed the Yerkes Primate Research Lab.

Cynthia Cheatwood of the Historical Society of Orange Park told News4JAX that the lab was once headquartered in the old Granary building off Kingsley Avenue, now a health food store.

“Some of the work that was done was cited in scientific journals the world over,” Cheatwood said.

Yerkes National Primate Research Center (Slides provided to News4JAX by Cynthia Cheatwood with the Historical Society of Orange Park.) (Copyright 2025 by WJXT News4JAX - All rights reserved.)

Scientists came from around the globe to collaborate with the lab’s founder, Dr. Robert Yerkes.

Robert Mearns Yerkes, pictured in Orange Park, Florida, founded the Yale Laboratories of Primate Biology in New Haven, Connecticut, in 1928. A year later the facility moved to Orange Park, where it remained until Yerkes's death in 1956. The center was renamed in his honor and relocated to Emory University in Atlanta that same year. Courtesy of Yerkes National Primate Research Center (Copyright 2025 by WJXT News4JAX - All rights reserved.)

A short walk from the Granary in an office park, an unusual concrete building still stands, with stairs leading to nowhere on the second floor.

Related: Monkey sighting at Orange Park apartment complex sparks curiosity, questions

Steps on the second floor of a nearby building remain visible, leading to nowhere. (Copyright 2025 by WJXT News4JAX - All rights reserved.)

Th oddities surrounding the buildings have been a headscratcher for many.

“There’s a Tarzan-from-my-youth idea in your head,” Cheatwood said. “And what are they not telling me?

The Humanzee Conspiracy Debunked

Early media photograph of Oliver the chimpanzee. Oliver gained fame for his distinctive appearance as a chimpanzee. He was once promoted as a potential human-ape hybrid, though this claim was ultimately disproven. Image credit: Unknown origin via Wikimedia Commons. Fair use, illustrative. (Image credit: Unknown origin via Wikimedia Commons. Fair use, illustrative.)

(Above is an early media photograph of Oliver the chimpanzee. Although not connected to Orange Park’s old monkey research lab, Oliver made headlines after being a unique-looking chimpanzee. Oliver (1957–2012) was once promoted as a “humanzee” due to his somewhat human-like appearance and a tendency to walk upright.)

Decades of monkey research were conducted at the facility, sparking wild rumors over the years.

It sounds like a sci-fi movie. The most persistent conspiracy theory alleges that scientists at the lab were attempting to create a human-monkey hybrid, known as a “humanzee.”

Cheatwood dismissed the claim as pure fiction.

Yerkes Primate Research lab. (Slides provided to News4JAX by Cynthia Cheatwood with the Historical Society of Orange Park.) (Copyright 2025 by WJXT News4JAX - All rights reserved.)

“Yes, that one is on the web and occasionally it kind of goes viral,” she said. “It is a falsehood. There is no truth to it whatsoever. This idea of a humanzee did not happen.”

The lab’s location, hidden away in what was then a wooded area off Kingsley Avenue, added to the intrigue.

“It was in the woods here because Kingsley Avenue was a two-lane road out into the woods, and you couldn’t really see it because it was surrounded by a big fence,” said Nelson Hellmuth, who now owns the Granary building.

Hellmuth recalled the local gossip surrounding the lab and shared a story about Dr. Yerkes’ alleged experiments.

“The real gossip was the fact that Dr. Yerkes wanted to raise a young chimp as a human to see how humanized it would be,” Hellmuth said.

The True Oddity

However, the experiment didn’t go as planned.

“It didn’t work out too well because the babies started taking on the characteristics of a chimp,” Hellmuth said.

Hellmuth has searched the Granary for clues about the lab’s history for years. He hasn’t found much, but one oddity stood out.

“There’s a half a dozen electrical outlets in the upstairs bathroom,” he said. “Makes you wonder what that’s for.”

The Lab’s Research

The lab’s research involved frontal lobotomies on monkeys, administering various drugs, and even one case where a husband and wife—Cathy and Keith Hayes—raised a monkey named Viki as a human child.

Cathy Hayes, author of the 1951 book "The Ape in Our House" and her husband, Keith Hayes, adopted a two-day-old girl chimpanzee to be raised exactly as if she were a child of their own. (Copyright 2025 by WJXT News4JAX - All rights reserved.)

The lab involved extensive research and surgical procedures that would not be permitted today.

Cathy Hayes, author of the 1951 book "The Ape in Our House" and her husband, Keith Hayes, adopted a two-day-old girl chimpanzee to be raised exactly as if she were a child of their own. (Copyright 2025 by WJXT News4JAX - All rights reserved.)

The lab’s closure in the mid-1960s hasn’t stopped it from being a hot topic in the town. And the theories and gossip had many visiting the area to get a closer look.

Some locals have even attempted to tie a recent monkey sighting on Wells Road to the old lab.

Related Video: Monkey sighting at Orange Park apartment complex

Cheatwood, however, was confident all the monkeys were relocated when the lab shut down. The Yerkes lab continues to operate today as part of Emory University in Georgia, where research is still conducted.

Established in 1930, the Emory National Primate Research Center is the oldest scientific institute dedicated to nonhuman primate research and paved the way for the National Institutes of Health-funded National Primate Research Center (NPRC) program, according to the website.

Still, the mystery lingers.


About the Authors
Scott Johnson headshot

Scott is a multi-Emmy Award Winning Anchor and Reporter, who also hosts the “Going Ringside With The Local Station” Podcast. Scott has been a journalist for 25 years, covering stories including six presidential elections, multiple space shuttle launches and dozens of high-profile murder trials.

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