Comments by "EebstertheGreat" (@EebstertheGreat) on "PBS Eons" channel.

Ah yes, the four Fs: fighting, fleeing, feeding, and coupling up.
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Random question about crown groups: if the tuatara goes extinct, will crown lepidosaurs become synonymous with squamates? After all, all extant lepidosaurs will then be lizards and snakes. That is, since crown (and stem) groups are defined by living representatives, do their definitions naturally change over time, as species go extinct? Or once defined, is a crown group fixed?
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Even "saltational evolution"--major heritable changes in a single generation leading to almost instant speciation--turns out to be a real thing, albeit extremely rare.
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@TheHortoman But they don't dwarf modern animals. By that standard, Anomalocaris was a giant compared to the animals of its time. The difference is that Cymbospondylus would be a giant even by modern standards. That's what they mean by the first "giant" animal.
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The way she says "zooplankton" is kind of funny. I wonder if she's a zologist.
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@noahmiller5740 Plesiosaurs were enormous and breathed air. There is zero chance of there being an undiscovered extant plesiosaur population out there. It's not impossible that a population of megalodon could have survived, but it is highly implausible. They were larger than Great Whites and just as active in shallow water, so for there to be a cryptic population around now, it would have to have a completely different behavior while being of the same species, which isn't realistic.
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@АлтайскийКазак It shouldn't matter whether they are "alive" or not. All that matters is their evolutionary relationships. Viruses evolve and speciate, so we should be able to classify them in exactly the same way we classify living things. If they did evolve from living things but are no longer alive, that just means a non-living thing evolved from a living thing.
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Not necessarily. Some pathogens survive for millions of years. Herpes Simplex Virus 1 (HSV-1) diverged from HSV-2 about 6 million years ago, for instance, meaning there were herpes simplex viruses even before then very similar to the ones around today, and probably susceptible to similar types of immunity. And that's probably not too unusual. So there is no reason the disease would have to be especially deadly. That would help, but it's not necessary. It wouldn't actually have to be deadly at all. If an old world virus made infected simians significantly less likely to reproduce for any reason for millions of years, then surely they would evolve ways to resist it, especially an adaptation as simple as deactivating a single gene. What is necessary is that the pathogen was so widespread that all modern descendants of all catarrhines at the time have lost the gene. So either that pathogen (or group of related pathogens) affected many different species simultaneously or it occurred so long ago that modern apes and Old World monkeys only descend from one or a few species from that time.
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@patriciomunoz6648 It's called carcinisation. More specifically, it's crustaceans that tend to evolve to look like crabs, more specifically, decapod crustaceans (with ten legs), and more specifically still those in the infraorder Brachyura (called "crabs," though not all are true crabs and not all resemble crabs). Examples are hermit crabs, king crabs, porcelain crabs, hairy stone crabs, crab lice, and true crabs. Other extinct crustaceans also resemble crabs, so this process is not restricted just to Brachyura. It is not known exactly why this form is so favored. One common hypothesis is that long tails are easy to grab, while the more elliptical "crab" shape with no tail presents a harder target for predators. Without a tail, crabs can't swim like lobsters, but as bottom-feeders, that isn't a problem.
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I would like a video on the evolution of plastids. I know that most organisms, including all plants and algae, ultimately acquired their plastids from the same endosymbiotic event. But evolution has made these diverge considerably over time, including the chlorophyll pigments used (and thus the color). More interestingly, the genus Paulinella _ and the species _ Pseudoblepharisma tenue both had unrelated endosymbiotic events in their histories, acquiring an unrelated cyanobacterium and a purple bacterium, respectively. Finally, the diatom family Rhopalodiaceae has acquired non-photosynthetic cyanobacteria, though it's not clear what advantage they provide.
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Wikipedia says there are nine herpesviruses that infect humans. The most famous is Varicella zoster , which causes chickenpox and shingles. This video seems to not actually be about the whole family of herpesviruses (called Herpesviridae ), but specifically about the Simplexvirus genus. There are only two of those viruses that infect humans, called Human alphaherpesvirus 1 and 2 , though usually they are called "herpes simplex virus 1" (HSV1) and 2 (HSV2). I wish they had made that a little clearer.
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@curtiswfranks Yeah, this seems to be the best way to go. For instance, we could define crown lepidosaurs as the most recent common ancestor of the tuatara and the green iguana and all its descendants (equivalently, the smallest clade containing the tuatara and green iguana). That way, it doesn't matter if the tuatara or green iguana still exists.
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@Ryquard1 It is definitely not the case that all animals have ears. I've never seen an eared sponge. Most "complex" animals have some sort of organ used for hearing, though they aren't all related. Insects can hear, but the organs they use for hearing are evolutionarily unrelated to vertebrate ears. Maybe a better way of putting it is that all tetropods have ears.
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@thefreakmachine Rock is very much alive, in many genres. Disco is . . . pretty much dead. And it was only really alive for like a decade. "Celebration" is probably the only real disco hit from the 1980s that people remember. There is a reason "DiscoVision" got changed to "LaserDisc" real quick.
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@orsonzedd Would you make the same zealous argument for the word "satellite"? How about "foothill"? Sometimes we define structures not by their inherent features but by their position in the environment. "Planet" seems like a prime example of that. After all, the most characteristic feature of all for a planet is orbiting a star.
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@orsonzedd Right, "satellite" is an example of a word that defines something by its position, not by its shape. "Planet" is another. And of course I didn't make up "foothill." Foothills are smaller hills near the base of larger hills or mountains. I didn't think that was particularly obscure.
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@orsonzedd Reasonable people can disagree about what counts as a "useful" definition in this context. But my point is that it is not inherently bad to use orbital characteristics to classify celestial bodies. We do that already for terms like "moon," "submoon," "satellite," "primary," "companion," etc. Traditionally, the defining feature of planets was always their motion, not their size. After all, the Sun was certainly a lot larger than Mercury, but both were classical planets because of how they moved. So it's not like astronomers just got up one day and made up some dumb new idea about what planets were, and it's not at all obvious that planethood should only be about physical characteristics and not orbital characteristics.
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@JustinMShaw I've also seen "planetary body" and "planetary mass object' used to refer to objects that are geological planets but not necessarily astronomical planets.
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Tunicates are even weirder. They are chordates, yet they look completely alien and about as un-fishlike as animals can get.
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I think it's funny how in the two-domain system, Eukarya becomes a subdomain within the domain Archaea, more specifically in the phylum Heimdallarchaeota. A subdomain within a phylum. It's like putting the class Aves inside the order Theropoda. Really goes to show how useless taxonomic ranks have become.
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3:02 "I know it's going to be hard for you... " HOW DID HE KNOW?
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1:58 LECA is certainly not the "most distant" common ancestor of living eukaryotes. It is the least distant one. Hence, "latest" ancestor, rather than earliest (which would be even older than LUCA).
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I would love to see a video on the Baldwin effect. It sounds like a way that natural selection can produce the appearance of Lamarckism and creativity after a sudden change in environmental pressures, but I don't fully understand it.
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FreeQuest, are you talking about earthquakes? Or just local shaking caused by fracking?
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@masonloeffler8064 I guess my timestamp is off by one second. Should say 3:31.
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@AngryKittens The same challenges exist in classifying bacteria, and to some extent, all life. Genes aren't strictly hereditary in the usual sense, and horizontal gene transfer (including by retroviruses) is relevant. We certainly can't fit viruses into the tree of life right now, primarily because we don't know where they fit. It might never be possible to determine the relationships at the base of the tree. But perhaps at some point we will conclusively show that some viruses evolved from a particular bacterial clade, and in that case, there is no reason not to consider them members of that clade.
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It's interesting that educators always distinguish poison and venom as disjoint categories of toxin, while dictionaries and textbooks usually define venom as a type of poison.
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I can understand why we sweat, but why do our palms sweat? That seems obviously non-adaptive. We don't have hair follicles in our mouth. Why do we have sweat glands on our palms?
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I have to admit, I always thought it was pronounced "ankle-o-saur."
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I wish whenever the script includes a distinction between "humans" and "apes" or a phrase like "ape-like man" or something, they would try to clarify that humans are apes, and the distinction is just between apes in general and those apes with peculiarly human traits. Because this is a series about evolution, and it just feels odd to repeatedly hear humans contrasted with apes as if they were species in different phyla without even once someone pointing out that humans were a species (or genus) within the superfamily of apes.
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I'm just waiting for the horse-like Clydesdales.
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Why doesn't the video mention Varicella zoster or other herpesviruses that infect humans? It only mentioned HSV1 and HSV2, and it strongly implied that those were the only ones. But there are nine different herpesviruses that infect humans, including the two mentioned causing oral and genital herpes simplex, the virus causing chickenpox and shingles, the Epstein-Barr virus, and even one associated with Kaposi's sarcoma. It's a little like talking about the coronaviruses in the context of animals, and saying two infect humans, both of which only cause the common cold. It would give a somewhat misleading picture, right?
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Why do some people tell me there are probably fewer than a million extent species of bacteria and others that there are probably more than a trillion?
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That pseudo-Victorian Southern English accent is kind of upsetting to be honest. It's like Margaret Thatcher meets Julia Child.
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3:30 what is that Carboniferous animal doing on my Cenozoic grass?
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I would love an explanation of how (U-Th)/He dating works. As I understands it, it involves measuring the content of uranium and thorium parent and daughter isotopes in addition to helium that comes from alpha decay. There are some very short descriptions of it online mentioning that helium diffusion in rocks is very sensitive to the type of rock and also to the temperature (and presumably to pressure), so I don't know exactly how measuring the helium content improves upon traditional U-Th dating.
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@alexeysaranchev6118 Zoologists really like that term. You might think ants are bugs, but they're not "true bugs." Sawflies and dragonflies might seem like flies, but they aren't "true flies." Walruses are seals, but not "true seals." And there are true cobras, true eels, true salamanders, and so on. Oh, and there are also false animals. The false potto looks like a potto but isn't. And there are false scorpions, whip scorpions, and scorpions, but no true scorpions. Names are weird.
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In addition to pseudogenes like GULOP, are there also genes that do get expressed but produce nonfunctional proteins? It seems like these could be produced by roughly the same process, and as long as they aren't toxic and aren't produced in huge quantities, that there would be little selective pressure to deactivating them. I did find one study from 2003 proposing the existence of "junk proteins" like this, but I haven't found any research since then or any actual evidence.
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A fear of snakes makes sense, and an aversion to bugs in general makes sense, but why do some people have such a visceral fear of spiders in particular? Was there a time in human history where spiders were a significant threat somehow?
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@cmg1819 But then you would expect things like flies, mosquitos, and ticks to be much scarier than spiders.
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@cmg1819 There must be an adaptive reason, but it's a bit of a mystery. Maybe in the past, there were more venomous spiders. It is particularly odd that arachnophobia seems even more widespread than ophidiophobia (fear of snakes). That might be somewhat cultural though.
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The episode mentioned priapulids (penis worms) but not the related kinorhynchans (mud dragons). Kinorhynchans have a similar body plan and similar digging behaviors to priapulids and show up at roughly the same time in the fossil record in the middle of the Cambrian. How do we know the priapulids are to blame here more than the kinorhynchans?
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8:05 Aren't there more like 400,000 described species of beetles?
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Why aren't these dig sites economically valuable? I am glad people stepped in to preserve it, but it seems like that shouldn't have been necessary. There are an awful lot more places to dump trash than to dig up priceless fossils.
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