Tardigrades are some of the most compelling organisms to have ever evolved on Earth. Also known as water bears, these 1-millimeter long eight-legged creatures have been known to survive the vacuum of space, withstand boiling water for at least an hour, endure high amounts of radiation, and make it through unscathed from some of the most extreme colds imaginable. As a result, tardigrades have managed to find a home on nearly every place on the planet.
How did such an organism evolve? Scientists have been trying to answer that question for a long time now, with few clues. Now, a team of Korean and Chinese researchers believe they have some insight into how tardigrades developed into the hardiest animals ever.
Tardigrades are descended from an extinct organism known as lobopodians, which lived on the planet during the Cambrian Period (which lasted from roughly 541 million years ago to 485.4 million years ago). Lobopodians themselves are an informal group of ancient marine worms with several stubby legs that lived in the ocean. Up until now, however, we’ve never been able to drill down exactly what groups of lobopodians today’s tardigrades may descend from.
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The new findings, published this week in PNAS, are the result of an analysis of 79 different subcategories of lobopodians, including 40 species of tardigrades. The new analysis found the likely ancestors of two classes of tardigrade species currently alive today, and suggest that a group of Cambrian lobopodians called luolishaniids are the most recent Cambrian ancestors of water bears. In the intervening hundreds of millions of years, it looks like tardigrades evolved into animals with shorter limbs and fewer trunk segments, developing into organisms with more miniaturized bodies.
While the study is really more of a pure science finding to fill the gaps in tardigrade evolution, they aren’t without more practical implications. Tardigrades have learned to survive by essentially hitting pause on their metabolic processes until they are returned to safer conditions—something that had to have been learned over time, in the species’ predecessors. They’re also able to make proteins that do not degrade in what would normally be considered extreme environments—another quality that needed to have been learned over time. If we’re able to pinpoint when these traits were acquired, then we may be able to do a better job of pinpointing what kinds of genes are responsible.
And given the advent of gene-editing technologies like CRISPR, that knowledge could allow us to artificially emulate those qualities in other organisms, and even ourselves.
Some of these implications are quite practical, like using tardigrade proteins to safeguard vaccines from deterioration. Other goals, however, are more ambitious: According to the South China Morning Post, Chinese scientists recently began inserting tardigrade genes into human embryos in order to give embryonic stem cells more resistance to radiation and allow these cells to survive “lethal exposure to X-ray radiation.”
Hacking our genetics with a microscopic, eight-legged creature might sound pulled straight out of Spider-Man. Indeed, we should take the findings (supported by China’s Academy of Military Sciences) with a grain of salt. But the ultimate goal is to save lives, and studying the evolution of tardigrades is part of the process in narrowing down what kinds of genes are most worth experimenting with.
