In the last few centuries, humans have summited Earth's highest peaks and dived into its deepest trenches, but the more scientists study the animals we've met along the way, the more they realize how little we know about the planet's biodiversity.
They estimate that for every species we've discovered, there are about nine that remain under the radar.
This does not include the black bears, belugas, and bald eagles, all of which have already been written about in academic journals. The unknown is primarily made up of small organisms, such as insects, mites, and crustaceans.
But don't underestimate these guys or think they're inconsequential. These species are the nuts and bolts of entire ecosystems: they produce soil, pollinate crops, and feed almost everything. And most of them have yet to be identified!
"Most people think that life on Earth is described, and we have a good idea of how ecosystems are functioning," said Emily Hartop, a fly researcher and taxonomist at the Norwegian University of Science and Technology.
"The reality is that for most species on Earth, we don't know what they are, we don't know where they are, we don't know what they're doing. They are unknown.”
A little over a decade ago, when Hartop was living in Los Angeles, she and her colleagues set up bug traps in backyards across the city. They were mesh tents with openings, known as Malaise traps.
Over the course of just one year, the traps collected 99 species of scuttle flies, small insects in the family Phoridae that, to an untrained eye, look a lot like fruit flies. Forty-three of those species were new to science and had never been described before.
Advances in DNA sequencing have transformed the way scientists discover and classify life on Earth. Instead of analyzing one specimen at a time, researchers can now sequence thousands of animals simultaneously and compare their genetic "barcodes" with massive databases. If a barcode doesn't match any known species, it could represent a new species.
The process is still far from simple. Many species already described by scientists have never been genetically sequenced, meaning museums often hold physical specimens without corresponding DNA records. As a result, finding an unfamiliar barcode isn't enough to confirm a new species. Officially describing and naming one still requires extensive evidence and publication in a scientific journal.
Even so, DNA barcoding has dramatically accelerated species discovery, leading many researchers to call this the "Golden Age" of biodiversity research. That means there are likely plenty more incredible creatures waiting to be discovered—and plenty more lists like this one to come.
