 If DVR skills were beneficial for survival, would we eventually have some sort of dance-dance evolution? A few days ago, some biologists published a paper in the journal Nature that's gotten a fair amount of attention. It's titled New Deep Sea Species of Xenoturbella, and The Position of Xenokillimorpha. I'm not even sure if I'm saying those words correctly. But because this newly discovered creature happens to look like this, the scientists who discovered it have developed a pet name that's a little bit easier to parse. They call it the Purple Sock. The Purple Sock is an oddly simple critter, one of about a handful of similar species that we've known about for a century or so. It's a worm-looking thing with no eyes, no brain, no gills, pretty much nothing but a mouth that consumes food and expels waste. And a lot of biologists are flipping out about it. Okay, so why is this silly looking thing making such a ruckus? To answer that, let's take a close look at the driving force behind biology itself, the theory of evolution. Evolution is one of those theories like gravity that is super obvious in retrospect but was elusive for a long time. The basic principle is simple. Small variations in species driven by genetic mutations occasionally make them better or worse suited for survival in a certain environment. Over a long enough period of time, because the creatures with helpful variations tend to reproduce more, those variations become more and more exaggerated, eventually leading to entirely new species. It's so simple and so intuitive. While we haven't had millions of years yet to see it happen naturally, we can certainly see the process at work and even harness it to our own ends. Evolutionary algorithms, genetic engineering, selective breeding, it definitely works. But there are some details about how evolution works, some implications and complications that may not be obvious at first blush. First, it's easy to make the mistake of thinking of evolution as an optimization process, something which always results in the best adapted creatures for any given environment. That's how we usually think about it when we're evaluating the physical makeup of different species. We see some trait and we think, why is it like that? It must have a really good reason for being like that and not some other way. The thing is, that's not necessarily true. When you're talking about what sort of genetic mutations will be selected for survival, it doesn't always strictly matter what's best. In some cases, it's what comes first or easiest that matters most. For example, you've probably noticed that most plants are green. This is because chlorophyll, the chemical which allows them to turn sunlight into energy, is really really good at absorbing most wavelengths of light, but not green light. Which is weird, because if you look at the energy available in various wavelengths of light here on the surface of Earth, green light has the most energy by far. If plants were engineered like solar panels to get the most light energy possible, they wouldn't be green, they'd be black. But chlorophyll has the advantage of being a relatively simple molecule to put together. Even if some enterprising prehistoric plant life was on track to synthesize an optimal version of a sunlight energy conversion molecule, something which utilized all frequencies of light, by the time it got halfway to a decent version, it would already be dead, crowded out by other more successful plants that went with the good enough chlorophyll. That's another interesting implication of evolution. There has to be an unbroken chain of advantage from beginning to end. Even if you can see a path to a fantastic adaptation, if any step along that path puts you at just a slight disadvantage to other creatures, you might as well not bother. This is why you don't see animals with wheels, even though a cheetah with wheels would totally run house on the savannah. There's no such thing as an almost wheel which can compete with an almost leg for locomotion, so any cheetah ancestor which had almost wheels would quickly die out trying to compete. That's not to say that every mutation must be beneficial to stick around, it just can't put you at a disadvantage at any point along the way. Finally, because evolution is a strictly iterative process, which depends on all previous versions of a species having been survivors, with each new variation on that species, all of the previous adaptations are generally locked in. Because you're competing with other members of your own species, if you regress back to a previous disadvantaged state, even if it's to try something else that might be better, you're already dead. This last bit is why the purple sock has been such a puzzle for biologists for such a long time. There's been a lot of confusion about its taxonomy, that is, how to group it, what relationship it has to other forms of life, what house it should be sorted into, sorry, phylum. It seemed at first like sorting various creatures into categories is a weird thing to be excited about, like biologists or over-excited librarians or something, but the structure of the so-called Tree of Life tells us a lot about how various species became what they are, and when. Each branching of the tree represents a common ancestor, some species which had a really useful adaptation that was so successful at surviving and procreating that its offspring could go on to develop even greater complexity, sort of like a functional chassis to bolt other crazy stuff onto. The further back you go, the more basic that chassis. Before this paper, the purple sock's evolutionary ancestor was thought to be way up here, which is a problem because this branch of the tree has things like eyes in the digestive tract that Xenotubella clearly doesn't have. That didn't really square with our understanding of the implications of evolution. Remember how evolved traits are generally locked in from that point forward? The idea that Xenotubella would have evolved these traits to give it an edge and then lost them, that was a problem. However, these researchers have compared the purple sock's genes to the genes of other creatures from other regions of the tree. This is a useful way to establish where something should be sorted. Even if you grow out of your evolutionary ancestor's gills, you still have some markers in your DNA for them. From that research, they concluded that Xenotubella branched off way earlier to do its own thing, around about the time that jellyfish and flatworms were figuring their stuff out. On the one hand, this is good news because it means that our understanding of the implications of evolution is probably still right. On the other hand, that's great news. It means that the purple sock represents a huge step forward in our understanding of the order of processes that led to more complex animals, like us. Biologists depend a lot on archaeology to supply them with fossils, so they have some idea of which animals were toodling around at certain periods in Earth's history. Unfortunately, they don't get to pick which fossils they end up with. A trilobite? Another f***ing trilobite? I have a hundred of them! I'm up to here with f***ing trilobites! Could you please just find me a transition between bilateria and deuterostomia? But if we have evidence that a living creature is an offshoot of a really, really old branch of the tree, we can compare its genes to the genes of other, more recently evolved creatures and get a rough idea of what life had come up with by then and what still needed figuring out. That's really useful information, believe it or not, by understanding how the genes for certain traits came about, we gain a better understanding of how to manipulate those genes for our own purposes, from medical research to genetic enhancement. And learning the sequence of how life came about on our planet gives us a better idea of what's necessary for that process so we can look for other similar or different forms of life elsewhere in the universe. Although, if we ever do find an alien species, I hope they don't look like the purple sock. I just can't take this thing seriously. What do you think of the subtler implications of evolutionary theory? Please leave a comment below and let me know what you think. Thank you very much for watching. Don't forget to blah, blah, subscribe, blah, share. And don't stop thunking.