On April 8, 1960, famed planetary astronomer Frank Drake turned the radio telescope at the Green Bank Observatory in West Virginia toward Tau Ceti and Epsilon Eridani, two Sun-like stars about 11 light years away from Earth. At that point, Drake had spent most of his professional career using radio waves to listen to the cosmos, but Project Ozma was unlike any task he had undertaken before.

Instead of listening for celestial bodies as they moved through the cosmos, Drake was searching for intelligent alien life.

By the time Drake shut down Project Ozma three months later, no extraterrestrial signals had been detected. It would have been a remarkable coincidence if the first scientific search for extraterrestrial intelligence in history had detected life around two of the closest stars to Earth, but that didn’t make the silence any less conspicuous. Then, as now, observation time on a world class radio telescope was a precious commodity. The question facing Drake and his colleagues was whether the search for extraterrestrial intelligence was worth the time, money, and foregone opportunities.

Following the conclusion of Project Ozma, Drake organized a conference with the intention of plotting the future of the search for extraterrestrial intelligence—or if it should have a future at all. The guest list was a who’s who of scientists doing cutting edge work in their respective fields. There was the young planetary astronomer Carl Sagan; Barney Oliver, the director of Hewlett Packard Labs; the astrophysicist Su-Shu Huang, who coined the term “habitable zone”; the chemist Melvin Calvin, who was notified that he won the Nobel Prize during the conference; and six others, including Drake.

When Drake delivered the guestlist to J. Peter Pearman, the National Academy of Sciences space science board officer who had requested the conference, Drake joked that “all we need now is someone who has spoken to an extraterrestrial.” But Pearman, ignoring the humor, had a suggestion: John Lilly.

Lilly, a trained physician with a background in neuroscience, believed his cetacean subjects were possibly “just as intelligent as humans” based on the complexity of their vocalizations and the large size of their brain relative to the rest of their body

Lilly was convinced that we shared the Earth with at least one non-human intelligence and possibly many more. Unsurprisingly, this conviction also made him the first to recognize the affinity between the nascent search for extraterrestrial intelligence and research on interspecies communication. In an op-ed published in the American Journal of Psychiatry three years before the Green Bank conference, Lilly argued that if we were unable to communicate with other possibly intelligent species on Earth, the prospects of communicating with an intelligent species on another planet seemed quite dim.

“Before our man in space program becomes too successful, it may be wise to spend some time, talent, and money on research with the dolphins [which] may be a group with whom we can learn basic techniques of communicating with really alien intelligent life forms,” Lilly wrote. “I personally hope we do not encounter any such extraterrestrials before we are better prepared than we are now.”

While dolphin intelligence, interspecies communication, and the search for extraterrestrial intelligence are all active and legitimate areas of scientific research today, at the time of the Green Bank conference Lilly’s ideas about nonhuman intelligence on Earth were considered fringe, even among other scientists working on interspecies communication. Still, Drake recognized the importance of Lilly’s work, and invited him to help plot the future of the search for extraterrestrial intelligence, a fringe scientific undertaking in its own right.

Arguably ten of the greatest scientific minds of the day were in attendance at the Green Bank conference, but Lilly quickly stole the show.  As Drake later recalled in Is Anybody Out There?, the group spent much of the first day “totally enthralled” with Lilly’s reports on his experiments with dolphin communication.

“The one among us who did the most talking about other forms of intelligent life was John Lilly,” Drake wrote. “He regaled us with tales of his bottlenosed [sic] dolphins, whose brains, he said, were larger than ours and just as densely packed with neurons. Lilly was convinced that the sounds [made by dolphins] constituted a complex language that he was only beginning to understand. We felt some of the excitement in store for us when we encounter nonhuman intelligence of extraterrestrial origin.”

Indeed, by the time the conference was over, the group had adopted the “Order of the Dolphin” as its informal moniker, a testament to the importance its members placed on interspecies communication as a SETI analog. For better or worse, this notion of dolphins as a prototypical extraterrestrial intelligence would shape the trajectory of interstellar communication for the next half century.

Only a few months after the Green Bank conference, Lilly published his seminal paper on dolphin communication in Science, one of the world’s most prominent scientific journals. In this paper, Lilly laid out the evidence he had amassed at the Communication Research Institute that suggested that bottlenose dolphins “talk” to one another using clicks, whistles, and other vocalizations.

For Lilly, the holy grail of his research was deciphering the meaning of the dolphin language, which would pave the way for true human-dolphin communication. In fact, in his Science article he claimed to have deciphered “a few tentative, simple ‘meanings’” for dolphin vocalizations, such as “distress,” “attention,” and “irritation,” but noted that “most of the exchanges are not yet understood.” Clearly, Lilly thought that cracking the secret of “dolphinese” was no longer a question of if—it was a question of when.

Not everyone in the scientific community was as certain about the success of Lilly’s interspecies communication project. In a telling review of Lilly’s Man and Dolphin, a book published just before the Green Bank Conference that catapulted his work into the public eye, the marine biologist H.O. Bull noted Lilly’s tendency to indulge in “vivid speculation” and deemed his book “one of the frankest and most egotistical accounts of a research project ever placed before a sensation-loving public.”

“In being so frank about his early failures, his treatment of dolphins, and his personal sacrifices, it may be questioned whether he has not done his cause a disservice,” Bull wrote, highlighting Lilly’s unfortunate tendency to vivisect his dolphins in the course of his research. In retrospect, his review of Lilly’s ethically suspect research methods was remarkably prescient—but no one could predict just how weird things were about to get.

Despite Lilly’s unorthodox research methods, his work on interspecies communication continued to attract funding from major government organizations—including NASA—throughout the 1960s. At the same time, Lilly began experimenting with LSD and other psychedelics after the wife of Ivan Tors, the producer of Flipper, introduced Lilly to acid at a Hollywood party.

“Ivan was financing some of the work on St. Thomas,” Ric O’Barry, founder of the non-profit Dolphin Project told the Guardian. “I saw John go from a scientist with a white coat to a full blown hippy.”

It wasn’t long before Lilly’s interest in the consciousness-altering effects of LSD began to bleed into his research on interspecies communication. As early as 1964, Lilly began injecting the dolphins he was studying with LSD to see how it would affect their communication. In 1965, Lilly delivered a report at a conference on “The Use of LSD in Psychotherapy and Alcoholism” that detailed his experiments.

According to Lilly, dolphins on LSD tend to be more vocal, especially when humans or other dolphins were in the water, too. Dolphin vocalizations are measured in terms of a “duty cycle,” which is the percentage of time that a dolphin is vocalizing per minute. Under normal control conditions, a dolphin’s duty cycle swings between zero and seventy percent. Yet Lilly discovered that when a dolphin is on LSD, its duty cycle “very frequently does not drop to zero at all.”

For Lilly, however, the real success of his research was how it positively transformed human and dolphin interactions. Lilly pointed to a dolphin that he had rescued that had been injured with a speargun by its previous owners and “would not come near human beings at all.” According to Lilly,  injecting the dolphin with LSD changed everything.

“As the LSD effect came on, 40 minutes after the injection, the dolphin came over to me,” Lilly told the attendees at the LSD conference. “She had not approached me before. She stayed still in the tank with one eye out of the water looking me in the eye for ten minutes without moving. This was a completely new behavior. She will now come within five feet of me instead of staying 20 feet away.”

Despite the apparent advances in non-verbal communication, Lilly’s experiments with dolphins and LSD did not yield much in the way of meaningful communication—at least linguistically.

“The important thing for us with LSD in the dolphin is that what we see has no meaning in the verbal sphere,” Lilly said. “The meaning resides completely in this non-verbal exchange. We are out of what you might call the rational exchange of complex ideas because we haven’t developed communication in that particular way as yet. We hope to eventually, but we accept communication on any level where we can reach it.”

As the 60s wore on, Lilly went to increasingly drastic measures to facilitate communication between humans and dolphins. In 1965, for instance, he waterproofed part of his laboratory so his assistant, Margaret Howe Lovatt, could cohabitate with a dolphin in the partially flooded facility 24 hours a day, six days a week, for two and a half months. Lilly hoped that sharing a living space around the clock would enable Howe and the dolphin to form a tight bond that would expedite efforts to teach the dolphin English. At the same time, Howe could take detailed notes about the dolphin’s behavior, which could provide valuable insight into the meaning of dolphin vocalizations.

On the floor above the live-in dolphin facility, Lilly created an “isolation room,” which was essentially a large sensory deprivation tank. There, Lilly would take LSD in total darkness and float on water he had pumped in from the Caribbean Sea. Evidently, Lilly’s fixation with the combined effects of LSD and sensory deprivation began to interfere with his research on dolphin communication. As Lilly recalled in The Scientist, Lovatt frankly told him that his self-experimentation was becoming a nuisance.

“Look, John, I am devoting my time, my energy, my love and my life to working with [the dolphins],” Lovatt told Lilly after he insisted on recounting one of his acid trips in the isolation tank. “If you want to do your experiments on solitude and LSD, please keep them in the isolation room. The rest of the laboratory is devoted to the dolphins and to my work with them. I am not curious or interested in what you are doing.”

Beginning in the winter of 1963, Carl Sagan began to pay occasional visits to Lilly’s lab on St. Thomas during his annual scuba retreat to the Caribbean. Although Sagan would later write in The Cosmic Connection that he had “admiration for any serious attempt to investigate dolphins and for Lilly’s pioneering efforts in particular,” it was his first hand experiences with Lilly’s research that convinced him that the Order of the Dolphin had overestimated the extent to which Lilly’s research would help them in their mission to communicate with extraterrestrials.

In particular, Sagan recounted an experience he had with a dolphin named Elvar, whose body language had made it clear to him that he wished to have his belly scratched. Sagan obliged the dolphin, but when he stopped giving him belly scratches, the dolphin raised itself out of the water and made a high-pitched squeak that sounded as though the dolphin had said “More!” When Sagan ran to tell Lilly about this, he informed Sagan that this was, in fact, one of the English words Elvar knew. Sagan, however, remained skeptical.

“Eventually, John believed that Elvar had learned some dozens of words of English,” Sagan wrote. “To the best of my knowledge, no human has ever learned a single word of delphinese. Perhaps this calibrates the relative intelligence of the two species.”

Although Lilly never was able to establish robust, two-way communication with his dolphins, his work did a lot to change the way we think about non-human intelligence, language, and interspecies relations. And as far as communicating with aliens is concerned, dolphins have made something of a comeback in recent years, due in large part to work of SETI Institute researcher Laurence Doyle and Brenda McCowan, an animal behavior researcher at UC Davis.

In 1999, McCowan, Doyle, and Sean Hanser, a researcher at Marine World Foundation, wrote a paper in which they used information theory to compare the complexity of animal communication systems, including humans and dolphins. Information theory is, broadly speaking, the study of how information moves through a communication system and one of its most interesting insights is what is known as “Zipf’s law.”

Nearly a century ago, the Harvard linguist George Zipf noticed a remarkable feature of human languages: namely, the most frequently used word in the language is used twice as much as the second most frequent word, three times as much as the third most frequent word, four times as much as the fourth most frequent word, and so on. When this frequency relationship is plotted on a graph, it yields a steep downward line with a slope value of -1.

As McCowan, Hanser, and Doyle realized, this unusual feature of human language could be a good ruler to measure the complexity of bottlenose dolphin communication. To test this, the researchers used a collection of recordings of dolphin vocalizations and treated each different vocalization as a discrete unit of information, similar to a “word.” When they plotted the frequency distribution of dolphin whistles, the slope was -0.95—staggeringly close to the frequency distribution of words in human languages.

This remarkable finding suggests that dolphin communications may be roughly as complex as human languages, but there’s an important caveat. This coincidence is only found when the frequency of dolphin “words” are analyzed in isolation.

Analyzing human languages based on the frequency of pairs of words, triplets of words, and so on indicates a deeper level of structural complexity in the communication system than just the frequency of individual words. There is a strong consistency in this higher order complexity across languages as diverse as English, Spanish, and Russian. Yet when dolphin “words” are analyzed in pairs, triplets, and so on, their frequencies quickly deviate from the values found in natural human languages. This suggests that human languages are far more structured and complex than dolphin communication systems.

In a paper published in 2011, McCowan, Hanser and Doyle argue that using these tools from information theory to analyze non-human communication systems could be of immense importance for SETI. In particular, they argue that this sort of analysis could serve as a sort of “intelligence filter” that could help SETI researchers determine if an incoming signal from space has the internal complexity characteristic of language.

This could help separate an artificial signal from a natural signal and eliminate a lot of false positives. For an example of how important this is, consider the case of CP1919, a pulsar discovered in 1967 by the Arecibo Radio Observatory that was mistakenly believed to be a candidate extraterrestrial signal. While the flashes from the pulsar had many of the characteristics of an extraterrestrial message, an information theoretic analysis of the signal  would have shown that it was too redundant to contain complex information.

Lilly’s experiments with dolphins on acid ultimately pushed the Order of the Dolphin away from interspecies communication as a model for SETI, but this was bound to happen eventually. Advances in linguistics in the second half of the 20th century firmly established human language as something qualitatively different from animal communication systems. For example, the rise of brain imaging techniques has shown that the hierarchical, recursive syntax of human languages, which linguists like Noam Chomsky believe set it apart from animal languages, is distinctly represented in brain activity. Still, as Doyle, McCowan, and Hanser’s information filter goes to show, animal communications are still a fruitful research direction for SETI researchers.

This information filter is a far cry from the sort of SETI applications that the Order of the Dolphin was looking for in interspecies communication, but it is born of the same fundamental impulse that motivated Lilly’s research: A profound desire to connect with other intelligent life, no matter how radically different they may be from ourselves.