A man wearing a giant sponge costume drifted through a sea of tuxedos in London’s Natural History Museum. He might have been out of place on a normal day at the museum. But on the evening of Oct. 4, 2010, the scene was an odd blend of formality and whimsy. A statue of Charles Darwin loomed over the hall, its massive, Gothic stone arches draped in sea-themed decor. A song about sea life played in the background, recorded by a former Talking Heads member and his band specifically for the event.

A man in a smoking tuxedo surveyed it all, feeling like a clown. Camilo Mora was the event’s featured guest, and the hundreds of scientists, reporters and guests were here to celebrate a discovery that hadn’t actually happened — a discovery Mora was supposed to have made.

Mora had grown up as a peasant farmer in Colombia in the 1970s, and studied biology at the University of Windsor in Canada. At the age of 34, he became a postdoctoral fellow at Dalhousie University in Canada. The fancy museum party was not a place he felt particularly comfortable.

Audrey Rollo

“This was the first time in my whole life that I wore a smoking tuxedo,” Mora remembered. He felt like Tarzan emerging from the jungle to attend a royal wedding. “I was shoeless for most of my childhood, so for me to be in this event, dressing like that … it was really something.”

The Census of Marine Life closing ceremony was meant to celebrate the fact that humans had, for the first time, estimated how many species there were in the sea. The Sloan Foundation, which partially funded the $650 million, 10-year project, organized the event. Scientists had been trying to uncover this magic number for at least 250 years. Previous estimates had put the number somewhere between 3 million and 100 million species on Earth ― a nice way of saying they had no idea. But on this day, Mora and his team were supposed to unveil a much more specific conclusion.

Reporters swarmed the museum, hoping to get the scoop on the scientists’ discovery. The spokespersons for the scientists did the only thing they could do: regale the crowd with other findings, facts the researchers drummed up when they realized they couldn’t find the magic number they’d been looking for.

A huge proportion of the volume of our planet is still to be explored. Camilo Mora

Mora told me later it was like going to an awards ceremony knowing he’d lost.

“You get the excitement of being there, hanging out with friends,” he told me. “But it doesn’t compare to winning the Oscar. We knew in advance that we hadn’t won the Oscar.”

Humans know much less about the animals in the sea than about those on land, largely because it’s just so hard to get to the depths of the oceans to discover what’s really down there. Research vessels that venture more than a few miles from the coast are expensive, and investigating the deep sea is even more difficult and expensive.

“A huge proportion of the volume of our planet is still to be explored,” Mora said.

Jesse Ausubel, the Sloan Foundation program manager who came up with the idea for the study, had deployed thousands of scientists from 80 countries on 540 expeditions to collect data. The information flowed back to a team in Canada run by Boris Worm, a marine ecologist and Mora’s boss, who sought to turn it into one magic number: the number of species in the sea.

“It was by far the most ambitious program of its kind ever convinced,” explained Ausubel.

In addition to the lavish closing ceremony, the researchers had a promise from Nature, the Harvard University of scientific journals, to publish the finding ― which is “just like winning a gold medal in the Olympics,” said Mora.

But the study didn’t go as planned. To calculate the number of species on the planet, you can’t just count up the ones humans have found; you need to find a way to estimate the species that are still undiscovered. And while Worm’s team had reams of data researchers had brought in from the field, they still couldn’t figure out what to do with it.

“The more we look, the more species we find,” Worm said. “There’s no end in sight.”

They tried taking the tally of species in one small area and extrapolating it to others, but the regions of the world were just too different. They tried looking for some relationship between the body size of a species and number of species in a given area, but that method broke down as the species got smaller.

The question plagued them: How could they make a realistic projection about exactly how many species were still left to discover? After years of work, they were no closer to figuring it out on the day of the closing ceremony.

“That question was my nightmare for all of those years ... We made all kind of discoveries. But the ultimate goal was not achieved,” Mora said. “After all that, we just came to that place to say, ‘Sorry, we could not figure out that number.’”

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After the ceremony, Mora and his colleagues gave up. They went back to their lives and started new projects. When Mora wasn’t busy with his own research, he’d peruse scientific journals.

A year or two after the museum debacle, on a morning still imprinted on his brain, Mora came across a two-page paper written by ecologist Carlo Ricotta and colleagues at the Sapienza University of Rome in 2002. The researchers sought to estimate how many plant species grew in an Italian mountain range. It was a tiny paper in both length and response — almost no one had read or cited it, Mora said.

“The paper was just hidden in the middle of nowhere,” said Mora.

Scientists organize every animal, plant, bacteria and other living thing into groups. Humans, for instance, are a species. But we’re also part of the larger order of primates, which includes monkeys, gorillas and chimpanzees. Primates are in turn part of the class of mammals, which also includes creatures like cats, giraffes and wolves.

Ricotta and his colleagues suspected that, if they knew the number of plants in a given area, they could figure out how many genuses, families, orders, subclasses, classes, subphylums and phylums there were, too. If they were able to determine that, they hoped the reverse might also be true: knowing how many larger groups were represented would allow them to figure out the number of species ― particularly kinds that humans hadn’t already managed to count.

They already knew from existing data sets that there were 921 species in that Italian mountain range; the mathematical formula the Italian group developed predicted 856. It was close enough, as estimates go.

Mora had a thought: If this method worked for plants on a few mountains, could it work on all marine species or even all life on Earth?

“I saw the paper maybe at 9 in the morning. I said, ‘Well, I already worked five years on this, let me work till midday,’” he recalled. If it didn’t work by noon, he’d give up.

Mora had a good way to test the theory. Though scientists don’t know how many animals there are on Earth, they do have a good idea how many mammal species there are: 4,840. So Mora whipped up a program quickly to calculate the number of mammals on the planet. If his program spit out a reasonably proximate number, then he was onto something.

He spent an hour pulling data together before cueing up the program. He clicked enter, and goosebumps popped up on his arms as saw the number on the screen: 5,000.

One test could easily be a fluke. So Mora tried birds next. Scientists have a reasonable estimate of the number of bird species on the planet ― 9,988. Mora once again set up the program and pressed enter. This time, he closed his eyes.

“There was so much anticipation that I didn’t want to see the number,” he told me.

He opened his eyes. The number was on the screen: 10,000.

“I have never won the lottery,” Mora said, “but I’m sure that probably felt pretty close to winning a million dollars.”

Mora dashed down the hall to his boss’s office.

“I need to show you something important,” Mora told Worm. When he saw Mora’s computer screen, the hair on the back of his neck stood up.

“I remember looking at each other and being in awe,” Worm told me later. “It was immediately clear that this was a major advance.”

He was seized by a sense of urgency.

“We need to tackle this right away,” Worm told Mora.

They immediately started cranking out a paper, Mora said. They were already about 80 percent done by noon. Since they knew they could figure out the correct number of mammals and birds just from plugging in genuses, orders and other taxonomic groups, they could now estimate things like fish and bacteria using the same methods. Just as their method could estimate mammals without data about all the existing mammal species, it could estimate the number of fish that were still undiscovered. Within a month, the scientists knew how many species there were in the sea.

But they didn’t stop there. They used the method to estimate the number of animal, plant, bacteria and all the other species on the planet.

Their conclusion: there are 8. 7 million species on Earth, and humans have yet to discover about 86 percent of them.

As he stared at a graph that summed up their findings on a recent morning, Mora got goosebumps again.

“It was one of the highlights of my life,” he said. “I wish I could share the feeling with everybody.”

The more we look, the more species we find. There’s no end in sight. Boris Worm

The paper made headlines around the world when they published it in PLOS Biology in 2011. There were thousands of news articles on it, including in The New York Times, National Geographic and The Washington Post. A thread on Reddit, “How do we know that we only know about 14% of our species?” was upvoted nearly 14,000 times. El Espectador, a Colombian newspaper, even named Mora one of its “people of the year,” along with the Colombian president.

But at least one person missed out on all the hype: Carlo Ricotta. Even seven years later, Mora still has no idea who Ricotta is. He’s never talked to him. He hasn’t come across more published work from the Italian ecologist. I couldn’t find anything Ricotta had ever said about Mora’s study, either. Was he proud his paper had gone so far? Disappointed he’d been left out of the excitement?

I emailed Ricotta. “I’m writing an article about how many species there are on Earth, and I noticed you’ve studied that question,” I wrote.

“Unfortunately, I have never studied that question,” he wrote back a few hours later. “So, I will probably be of very little help for your article.”

I spent an inordinate amount of time trying to explain everything to him over email, pointing out that he wrote a paper on the subject over a decade ago that spawned a finding about species all over the planet. He eventually agreed to talk with me on Skype.

“I have nothing against telling you what we did,” he wrote. “But this is probably very different from what you expect.”

When we finally talked, he was friendly but confused. He explained that his paper just looked at seeds on a mountain range, not all the species on Earth. When I told him scientists had used his method to calculate the number of species on the planet, he told me that he doubted it would work. We ended the conversation quickly, and I sent him Mora’s paper, as well as some news articles about it.

The next day, he sent me an email consisting of only five words “Hi. I did my homework.”

We talked again a few days later, finally on the same page. He told me he liked Mora’s paper well enough.

“I think it makes sense,” he said. “It’s a very elegant approach.”

But he still didn’t seem particularly excited about either the study or his own contribution to it. It had happened so long ago and was such a small part of his life that he barely remembered it. The paper had started as an undergraduate student’s thesis. He and another professor had simply worked with the student to use existing data to come up with a mathematical formula.

Unlike Mora’s endeavor, there weren’t thousands of scientists or billions of dollars involved. Just some basic math.

“You can have fun even with low-cost science,” he mused. “I’m happy it was used to build something.”

Others in the scientific world were more effusive in their praise of Mora, Worm, and their coauthors’ paper.

If I tell you there are 20,000 species being lost every year, is that a lot, or not? Camilo Mora

“It is a remarkable testament to humanity’s narcissism that we know the number of books in the U.S. Library of Congress on 1 February, 2011 was 22,194,656, but cannot tell you — to within an order-of-magnitude — how many distinct species of plants and animals we share our world with,” wrote Robert May, a zoology professor at Oxford University who had been trying to calculate this number since the 1990s.

As Worm put it, if aliens came to Earth, one of the first questions they would ask is how many species are on the planet.

“I think the paper has helped renew an interest in taxonomy,” Worm added. A lot of scientists are now doing research that sounds much cooler ― tweaking DNA and working on artificial intelligence. But finding new species is still deeply important, Worm said. Newly discovered species have helped us develop new pharmaceutical products and food sources, among other innovations.

Mora himself considered the mystery “one of the most basic questions of biology” that was still unanswered. To be clear, it’s still unanswered: Mora, Worm, and their coauthors’ paper got us closer to a solid estimate. Scientists continue to learn more about the number of species on Earth every year.

For Mora, there’s another impetus for understanding. We need to know how many species exist to know how many are going extinct, he said.

“If I tell you there are 20,000 species being lost every year, is that a lot, or not?” Mora said.

“I just can’t believe we don’t feel that pain that many of these species are going through. We just get turned off by it. And that’s not going to make it any less of a reality,” he said. “We live our lives like we’re the only ones here.”