Transcription
Ladies and gentlemen, I present to you the colugo. Cool, right? Just look at how it leaps between the trees. So, what do you think, what kind of relative is this cute little gliding creature? It's obvious that I've already spoiled the answer in the video title, but in any case, the fact that the closest sister group to colugos are primates, somehow doesn't inspire confidence. No, well, you could say, with a stretch, that this wonder vaguely resembles a Loris or a Lemur, but I'm sure the average person would still say it's some kind of flying squirrel, because they really do look very similar. But how did it happen that these little animals, starting from our ancestors from one initial point, at least from one common ancestor, living in sufficiently similar conditions with our ancestors, ultimately diverged from us and ended up so different from primates that they were even classified into a separate order, albeit with difficulty. Well, to answer this question, we'll have to, as is classic for the genre, start the story from such deep antiquity that I even had to draw a cladogram of kinship. The inhabitant, and I myself, did not lose the thread of the narrative along the way. So, let's begin with dreams. We transport ourselves back in time approximately 66-80 million years ago. This is the Late Cretaceous period, just shortly before a huge cosmic asteroid called Chicxulub will hit the planet, which will greatly alter the balance of power among animals and plants. This massive event will later be called the Cretaceous-Paleogene extinction. And indeed, the reason for the extinction was not only the meteorite. In fact, it's a process that had been going on for millions of years by that point, with many different causes. But for us, all this tediousness is not so interesting right now. And not important at all. After all, the story of our ancestors and the colugos begins before this extinction. Despite the fact that the first true mammals appeared in the Late Triassic around 225-210 million years ago, their life was clearly not a fairy tale. Quite the opposite, if the ancestors of mammals, for example, cynodonts, were quite solid, progressive predators, then our companions, living precisely in the period between 80 and 65 million years ago, were almost completely squeezed out of predatory niches by a more successful group of archosaurs, which you all know perfectly well. Dinosaurs. Yes, it was dinosaurs of all kinds and sizes that would so mercilessly oppress mammals that in the end many would die out, and the remaining unfortunate ones would be forced to become small insectivores, omnivores, or, if they were very lucky, small carnivores, like, for example, Eomaia. It's interesting to note that at this stage, what mammals would consider extremely fashionable and progressive immediately after the Cretaceous-Paleogene extinction, namely arborealism, was poorly developed among Mesozoic mammals. The reason is simple. Small dinosaurs do it much better, and therefore hiding from them in this way would simply not work. Moreover, dinosaurs are mostly diurnal animals. So, in addition to adapting to omnivory, Mesozoic mammals had to change their daily rhythm to nocturnal or at least crepuscular, simply to avoid competing with much scarier little dinosaurs. But if you think that our mammalian ancestors were brought down as low as possible, then you would be not entirely right, because there is a known case when mammals did attack dinosaurs, albeit young ones. But even if we don't take this into account, due to immense competitive pressure, the ancestors of modern mammals were forced to acquire adaptations that would provide them with mega-plasticity in adapting to changing environmental conditions. To make it easier to understand what I mean, imagine that early mammals are a spring, on which a large stone in the form of dinosaurs is pressing down. As long as the stone lies motionless, the spring will be compressed. But if something happens to the stone and it loses stability, then the spring will shoot out so that it won't be a pleasant experience. In the end, this is exactly what happened. Immediately after the peak of extinction 66 million years ago, all non-avian dinosaurs died out, or were still actively dying out. This freed up a huge number of ecological niches in a short period of time. And the spring of mammalian potential finally shot out. And so much so that in just a couple of million years, mammals occupied all the niches that previously belonged to dinosaurs. And where are the ancestors of our colugo companions here? Well, they missed the moment and the opportunity to become predators a little. After all, they initially started from a position of omnivores, or rather even insectivorous placentals. Observing how other branches of mammals transformed from small crepuscular predators into creatures like mesonychids, the most famous of which, perhaps, was Andrewsarchus, and also still being persecuted by the remnants of crocodiles, birds of prey, and even snakes, which at this time were already acquiring a more or less modern appearance. Small omnivorous ancestors of primates frantically searched for a place to escape from everyone, and came up with nothing better than becoming tree-dwellers. Especially since this niche was somewhat freed up after the extinction of most dinosaurs. In short, they settled there. They lived happily, so happily that they dared to allow themselves an unprecedented audacity. To give birth not quantitatively, but qualitatively. Well, why not, now that you're sitting in a tree, you don't have to give birth to a whole company in the hope that someone will survive, but give birth to one well-fed baby, on whom more resources will be spent anyway than on 300 small ones, give him a longer childhood, during which you can pass on invaluable life experience to the offspring. And you know what this all smells like? These are the beginnings of socialization and later intelligence. The most striking example of such an animal was the well-known Purgatorius. In essence, it is considered the oldest primatomorph, albeit imperfectly. It can be said that somewhere around this is how all the ancestors of primates looked, more or less, at the beginning of the Paleocene. The particularly attentive may notice that modern colugos look suspiciously like these Purgatorius, and they would be right. And here's the thing. In essence, colugos are a sister branch of Purgatorius that separated quite early, which, unlike the latter, in order to avoid competition, turned to herbivory, most likely, to feeding on leaves. It's obvious that they did this gradually, with each step moving further and further away from fruit consumption to leaf consumption. Everything would have been fine, but the idyllic paradise in which the ancestors of primates had lived until then was coming to an end. On the border of the Paleocene and Eocene, the first viverrid-like creatures appear from the order of Carnivoraformes, which will become a real nightmare. To understand who we are dealing with, here, for example, is one of the representatives of the weasel family. They are, of course, small, but even now they can bite off a baboon's neck with ease, and back then even more so. Moreover, as if by evil, these fellows are excellent climbers, so arborealism no longer saves. And that's it, the terror began. New predators heavily oppressed not only the ancestors of colugos, but also the ancestors of primates. Since the ancestors of both were quite similar in structure, the ways of solving the problem of encroaching predators were also, in essence, the same for everyone. Either to increase in size, because if you are the size of two wardrobes, then not every predator will want to mess with you, or to speed up, to simply manage to escape in case of the slightest danger. If the first monkeys equally implemented both these strategies, which would more likely lead to the appearance of Plesiadapis, and a little later the first true primates, such as, for example, Achiacebus achilles, then the proto-colugos will go almost entirely down the path of acceleration. And how! In essence, they became victims of excessive narrow specialization. In an attempt to escape from an opponent around 52-50 million years ago, a leathery membrane begins to form between their limbs, allowing colugos to glide from branch to branch. In essence, yes, an analogue of a modern flying squirrel. And you can't say anything bad about it. It was indeed a good idea. But only in the short term. In practice, playing the long game almost completely destroyed them, not as a species, but as an entire order. The thing is, under what specific conditions they adapted. It should be understood that the average temperature in the Eocene was on average 13-14° higher than current values. And this doesn't mean that it was like an oven at the equator, but rather that heat was distributed more evenly across the planet. And therefore, tropical forests covered not only the central equator, but also a large part of the planet. And there was no talk of ice caps at the poles. Thus, the habitat of these companions was enormous, but over the next couple of tens of millions of years, the temperature on the planet will drop very significantly, as will humidity. And therefore, the tropical forests on which this order of mammals depended will become much smaller. Overall, climate change occurred more or less smoothly from place to place, but certainly smoothly enough to adapt to new conditions if desired. But here comes another problem. The thing is that the adaptation of a parachute flyer in the form of leathery membranes imposes huge limitations on your further variability and, in essence, very much narrows your adaptive capabilities. After all, you can't easily get rid of the membrane. Growing in size is also not an option, because to maintain the aerodynamic quality of the membranes, for increased mass, you would have to grow membranes of such sizes that they would get tangled under your feet. Escaping the situation with enhanced intelligence, like humans, is also not an option, because this requires increasing the size of the head, which is not only inconvenient when you are the size of a large squirrel, but will also be a burden in flight. Thus, the initially good idea of gliding between trees turned out to be a родовое проклятие (hereditary curse). Leading to the extinction of these animals everywhere except in places where environmental conditions have hardly changed since the early Eocene. And are there such places? Of course, there are. And you have all heard of them for a long time, because this is Southeast Asia, in particular, the Philippines and Indonesia. Yes, thanks to the fact that the islands of this region are surrounded by warm seas, the climate there has practically not changed or has changed minimally. Today, two species of colugos inhabit this region: the Philippine colugo in the Philippines and the Sunda colugo. Guess for yourself where they are from. But before moving on to the conclusion, I want to remind you that I post all interesting information on the video's topic on my Telegram channel. Moreover, there you can discuss everything with me personally. For those interested, the link is in the profile header. So, summarizing all of the above, we can safely describe colugos as failed primates who, in the evolutionary race from predators, got so complicated that they outsmarted themselves and as a result almost went extinct. Nevertheless, the history of the development of this group of animals is as interesting as it is ironic. That's why I believe that their story should be known by everyone who is even slightly interested in biology and animal evolution. Learn biology with me, my dear viewers. I bid you farewell. See you soon in the next episode.