Hierarchical taxonomies are notoriously crap. But people like them because they appear to simplify things and make them understandable and easy to explain, if you don’t mind them being wrong.
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Don’t know what bacteria are.
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I’ll just step in to say the article about this I found:
It’s very clear and specific in the article that they’re taking about h.sapiens, though they also explicitly refer to Neanderthals and Denisovans as humans, too.
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Wow, that is harsh to a lot of work taxonomists have done. I think it’s almost the opposite: hierarchical taxonomies can be made to work fine in most cases if not very well. The problem is when people misuse then, and one of the ways is in thinking because they reflect ancestry, they must be unique and perfectly objective instead of useful descriptions.
For instance, the idea that any populations that can interbreed must be the same species is sounds nice in theory, but is tough to apply in practice. Especially if you include the past, since then any two animals are connected by a continuous set of interbreeding types. The question isn’t where there are breaks, but where the connections are thin enough to be usefully treated as breaks. That involves judgment. But just because there’s no definite line separating chairs and tables, doesn’t mean distinguishing chairs and tables is wrong.
Likewise for bacteria there is a lot of horizontal gene transfer in addition to vertical descent. But that doesn’t mean the descent of an organism isn’t a coherent notion, it just means that many of their genes will have different descent. Despite some early pessimism it looks like that’s still very much something we can coherently investigate. It’s just harder, which is why the taxonomy is still being worked out.
For Homo, unfortunately, there are a lot of problems with inertia and prejudice. People still act like modern races are disjoint, when they’re small variations in one connected population. Neandertals and Denisovans were genuinely more separated; it makes sense to treat them apart from H. sapiens sapiens, and maybe there’s an argument it’s useful to treat them as different species. But I don’t know of one; it seems it’s more just left over from when popular opinion was they couldn’t possibly have interbred, even though we have learned otherwise.
In short, then, I think the problem is less that taxonomy isn’t an invaluable tool in understanding the living world and more what MarjaE said – people leaning on ignorance or prejudice instead of trying to accurately represent our history.
I hope nobody minds me arguing this? I realize I’ve disputed a lot on this thread, and not much of it has been in a way that made for useful discussion. But here is something that grinds my gears: when an academic field is presented poorly, and then people decide the field rather than its presentation must not have merits. Taxonomy, climatology, pretty much all the social sciences. People work hard at them, and don’t deserve to be dismissed so casually.
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I’m sorry, I certainly don’t mean to disparage anyone’s hard work. But my job includes presenting information to people, and I’ve never once seen a nontrivial hierarchy that worked (but many many misguided assumptions that one would). In practice, there are always cases with multiple parents, cross-relations, ways that people might look at it from a different starting point, etc. Super-simple example: does the art history book get classified under Art, or History? Depends on who’s looking for it and what their internal thinking is. Multiply that times a thousand and you get the idea. That’s why we now have tags and freeform text search on the internet instead of just a hierarchical directory like Yahoo and DMOZ.
Hierarchies are a useful way to view a set of information, but in my experience, they’re never correct/accurate beyond a trivial level, unless something is intentionally limiting the data to a single hierarchical structure. Real-world data almost never fits that.
Not at all! 
The more viewpoints, the merrier!
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Ah, I see, we were not thinking of the same thing. You meant hierarchical taxonomies for data in general. There I would tend to agree, you either allow a more elaborate graph or you get bad results. Linnaeus divided the natural world into a hierarchy starting with animal, vegetable, and mineral kingdoms, and the last has failed for all the reasons you would expect.
But the other two have proved different. This is the biological taxonomy I was thinking about, where you genuinely do see natural arrangements in terms of over-all similarity. In trying to explain I realized I’m just recreating what Darwin wrote:
It is a truly wonderful fact - the wonder of which we are apt to overlook from familiarity - that all animals and all plants throughout all time and space should be related to each other in group subordinate to group, in the manner which we everywhere behold - namely, varieties of the same species most closely related together, species of the same genus less closely and unequally related together, forming sections and sub-genera, species of distinct genera much less closely related, and genera related in different degrees, forming sub-families, families, orders, sub-classes, and classes. The several subordinate groups in any class cannot be ranked in single file, but seem rather to be clustered round points, and these round other points, and so on in almost endless cycles. On the view that each species has been independently created, I can see no explanation of this great fact in the classification of all organic beings; but, to the best of my judgment, it is explained through inheritance and the complex action of natural selection, entailing extinction and divergence of character.
A tree-like hierarchy won’t work well for things like books or webpages. It works well in this case because we are labeling different parts of a family tree.
This still requires, like you said, limiting our data; you have to stick to features that relate to inheritance. Categories like carnivorous, planktonic, or wind-pollinated are very meaningful but won’t fit on single branches. Some features of bacteria appear to, and others are easily transferred from one to another, and still others are hard to tell. And with sexual reproduction single inheritance is only mostly true – as you zoom in, you find some species are hybrids of close relatives, and then of course each turns out to be a whole complex mesh of individuals.
But even so, most of the time a hierarchy based on inheritance captures a lot of the underlying reality. Simply see that an animal has feathers, and even with weird cases like penguins or hoatzins, I’d bet what you would assume about its anatomy, development, and biochemistry would be at least 95% right. Recognizing a natural taxonomy makes it possible to make predictions about organisms and discuss how they originated. Like I said it involves judgment calls, but there is very much a science to it.
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Easy to get rid of though, as it’s just your diaphragm spasming because it’s trying to go the wrong way.
When you breathe in, push your diaphragm down; when you breathe out, pull your diaphragm up. Works for me every time, often within a few breaths.
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No good points well made.
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I don’t know about @Melizmatic, but I have hiccuped in the middle of doing that.
Soft palate stimulation often works for me. Grab a raw sugar packet, shake it onto your tongue, and swallow it before the granules get a chance to dissolve. Usually takes two tries.
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So have I, but if you keep going it does work
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Yeah, just look at the Pluto planet/not-a-planet controversy.
Another example: In biology, it’s really hard sometimes to distinguish what “kind” of cell you’re looking at.
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Pedantic note: there is no such controversy. There is however a debate over the criteria for something to be a dwarf planet.
As with taxonomy, and I’ve probably said this before, the categories were first invented in an almost prescientific era. It takes a long time to adjust to new and better information. It’s becoming obvious from looking at other planetary systems that our understanding of them, to mix metaphors very badly, is only that of the very tip of a very large iceberg. In the same way, Linnaeus tried to classify plants by counting their sex organs*, which is a bit like trying to classify internal combustion engines by counting their inlets and exhausts. Until you understand about different thermodynamic cycles, you will draw conclusions some of which are right and some of which are wrong.
*I know this is litotes for dramatic effect. I do not intend to apologise.
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Well, I won’t argue over whether it’s a debate or a controversy! But good points, thank you.
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Something something multple inheritance, which we get with symbiotes and epigenetics.
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I wasn’t making that distinction, just observing that the Pluto thing is not planet-not a planet but planet-dwarf planet. As we discover more planetary systems I suspect we will need more classifications, and perhaps have to redefine Mercury-Mars as dwarf planets too.
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Alas another failed bad joke . . . . I guess the problem is what happens if we end up with one planet per class?
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I’m slow on the uptake today, I have a cold. Sorry.
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Except that controversy was a lot less trouble finding categories that conform to nature, and more that people didn’t want to give up the US-discovered planet they learned in school. Without that prejudice, it had been obvious it didn’t fit for a while.
I would be very surprised! Mercury and Mars, and for that matter Venus, Earth, and even our others, are much smaller than many planets out there. But the whole point of the IAU definition was not to pick an arbitrary size cut-off but to make it about solar system structure. If I may quote what I wrote at the old place:
Without making any attempt to classify them, here are all the largest objects in the solar system, save maybe a few that were discovered in the last few years; I've arranged them by mass in kilograms on a logarithmic scale:30 – Sun
27 – Jupiter, Saturn
26 – Neptune, Uranus
25 – Earth, Venus
24 – Mars, Mercury
23 – Ganymede, Titan, Callisto, Io, Moon, Europa
22 – Triton, Eris, Pluto, Sedna, Haumea, Makemake, Titania
21 – Oberon, 2007 OR10, Quaoar, Rhea, Iapetus, 2002 TC302, Charon, Ariel, Umbriel, 2005 QU182, Dione, Ceres, 2007 UK126, Orcus, Ixion, Tethys, 2005 UQ513, VarunaAll of these are large enough to be round, in contrast to the 20 bracket which includes objects like Vesta and Pallas that aren’t. The sun is of course a star made of plasma; the next four are primarily gaseous, and the others are variously rocky or icy.
From Ganymede downward, many of these don’t orbit the sun directly, but instead circle larger objects. The others in this size range are all part of two belts containing a multitude of objects of various sizes, with generally eccentric and overlapping orbits. Both kinds probably formed there, but with some interchange; as I said, Triton probably started as one of the outer belt objects before Neptune captured it.
The only exceptions to these categories are the eight objects from Jupiter down to Mercury. These go around the sun directly but are not part of any belt, with orbits cleared of all but very small debris. And this is probably an important part of how the system formed; they are not all expected to have formed in place by any means, but not from belts or left-overs like the others.
This is the way we expect most solar systems to form, though we are still just beginning to learn about them. And I think when there is more than one object known, so far this kind of structure does seem to be most common (e.g. our near neighbor), though that may be partly sampling bias – radial velocity detection presumes objects have a cleared orbit, and infrared excess presumes belts that generate a lot of dust.
But in any case, our solar system is shaped the way it is, and it belongs to a category with a surprisingly natural break between a few bigger objects and many smaller ones. Planet has a long tradition of being used that way (the IAU definition doesn’t count minor planets or dwarf planets as planets per se, which I think makes sense though is awkward English).
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Speaking of awkward English, I am amazed that people still refer to Earth’s sun and moon with generic rather than proper names, Capitalizing it doesn’t make it a name, any more than calling the Earth “Planet”, or me “Person.” Especially daft when there are already other existing names that can be used.
Or else make those “proper” proper names and use different general names, Since people already refer to other satellites as moons, and there are many of them, the former is the easier option.
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Sun and Moon started as proper names and it’s not unusual for English to take those and turn it into a category: mausoleum, casanova, quisling, Adonis, Judas. You would never call our world “Planet” but astronomers now talk about extrasolar planets as eccentric Jupiters and hot Neptunes, with probably Earths to come.
But I completely agree it’s very awkward here. I remember in that post being tempted to write Sol and Luna, which at least act as deity-based names in English even if they’re just translations. But those aren’t official or common outside sci fi and so felt like making it needlessly hard to understand. For now we dropped the ball.
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