# Why does evolution "look" so directed? **URL:** \ **Category:** Factual Questions\ **Created:** [October 15, 2013, 3:22am UTC](https://boards.straightdope.com/t/why-does-evolution-look-so-directed/671280 "2013-10-15T03:22:07Z")\ **Posts on this page:** 19\ **Page:** 4
**Author:** ![brazil84](https://avatars.discourse-cdn.com/v4/letter/b/8491ac/32.png) [@brazil84](https://boards.straightdope.com/u/brazil84)\ **Post date:** [October 17, 2013, 6:33pm UTC](https://boards.straightdope.com/t/why-does-evolution-look-so-directed/671280/61 "2013-10-17T18:33:43Z")
> [@Aji\_de\_Gallina](#): > > I know evolution is random and the whole Darwin-natural-selection thingy, but sometimes when you look at the process of evolution, for example in humans, it’s like evolution “decided” that we’d get bigger brains, lose hair, and go bipedal; and once it “decided” that we wouldnot go back. > > I also know that enviromental pressures load the evolutionary dice in one direction > > Is it simply a case that we only see the evolutionary “winners”? > > P.S.: No, not even remotely even a hint of ID. Part of it might be positive feedback. So for example, if people get smarter, they might develop more complex societies, which in turn puts pressure on people to get even smarter. Or if cheetahs get faster, it puts pressure on gazelles to run faster, which puts pressure on cheetahs to run faster still. ---
**Author:** ![Aji\_de\_Gallina](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aji_de_gallina/32/260_2.png) [@Aji\_de\_Gallina](https://boards.straightdope.com/u/Aji_de_Gallina)\ **Post date:** [October 18, 2013, 12:14am UTC](https://boards.straightdope.com/t/why-does-evolution-look-so-directed/671280/62 "2013-10-18T00:14:47Z")
> [@brazil84](#): > > Part of it might be positive feedback. > > So for example, if people get smarter, they might develop more complex societies, which in turn puts pressure on people to get even smarter. > > Or if cheetahs get faster, it puts pressure on gazelles to run faster, which puts pressure on cheetahs to run faster still. Cheetahs are a nice exmaple because it looks like they evolved themselves into a corner. They basically got as fast as they can be by shedding everything, I can’t see where they might go if they “wanted” to go faster, which is their thing, or if stronger they’d certainly lose speed. ---
**Author:** ![Darth\_Panda](https://avatars.discourse-cdn.com/v4/letter/d/ee7513/32.png) [@Darth\_Panda](https://boards.straightdope.com/u/Darth_Panda)\ **Post date:** [October 18, 2013, 12:22am UTC](https://boards.straightdope.com/t/why-does-evolution-look-so-directed/671280/63 "2013-10-18T00:22:35Z")
> [@Glazer](#): > > Does a Platypus look directed? By a guy on acid? Sure. ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [October 18, 2013, 10:29am UTC](https://boards.straightdope.com/t/why-does-evolution-look-so-directed/671280/64 "2013-10-18T10:29:55Z")
> [@ZenBeam](#): > > Human embryos still have gill slits, for example, after many millions of years on land. No, they don’t. They have [pharyngeal pouches](http://en.wikipedia.org/wiki/Pharyngeal_pouch_%28embryology%29) but these don’t develop into anything like gills in human embryos. Recapitulation theory is bunk. This isn’t to deny that the pouches’ prescence shows common descent, because it does, but don’t call them gill slits. ---
**Author:** ![bob\_2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bob_2/32/3341_2.png) [@bob\_2](https://boards.straightdope.com/u/bob_2)\ **Post date:** [October 18, 2013, 11:41am UTC](https://boards.straightdope.com/t/why-does-evolution-look-so-directed/671280/65 "2013-10-18T11:41:30Z")
> [@Sailboat](#): > > Well, there’s some evidence now that H. sapiens may have interbred with at least Neanderthals and Denisovians instead of just murdering them. > > Still, either way they were fucked. So - murder and rape as well…🙂 ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [October 18, 2013, 5:01pm UTC](https://boards.straightdope.com/t/why-does-evolution-look-so-directed/671280/66 "2013-10-18T17:01:31Z")
> [@MrDibble](#): > > No, they don’t. They have [pharyngeal pouches](http://en.wikipedia.org/wiki/Pharyngeal_pouch_%28embryology%29) but these don’t develop into anything like gills in human embryos. Recapitulation theory is bunk. This isn’t to deny that the pouches’ prescence shows common descent, because it does, but don’t call them gill slits. [See Pharyngeal slit](http://en.wikipedia.org/wiki/Pharyngeal_slit): > [@](#): > > However, it is now accepted that it is the vertebrate pharyngeal pouches and not the neck slits that are homologous to the pharyngeal slits of invertebrate chordates. **Gill slits are, at some stage of life, found in all chordates.** Here’s a page [Human embryos don’t have gill slits](http://evolutionwiki.org/wiki/Human_embryos_don't_have_gill_slits) on EvoWiki where people are arguing both for and against the term “gill slits”. The first response is particularly relevent: > [@](#): > > While it may indeed be misleading to refer to them as gills proper, few scientists or textbooks actually make that particular mistake, and the structures in question are indeed colloquially referred to as gill slits. Gill slits are simply the invaginations between the pharyngeal pouches. The pouches contain mesodermal tissue, the gill arches or gill bars. The term is legitimate because the slits do establish contact between the outside and the pharynx. The fact that the arches later develop into non-gill structures is irrelevant. I’m not going to argue semantics. You can call them what you like, but don’t say I’m wrong when I’m using a common term. ---
**Author:** ![md2000](https://avatars.discourse-cdn.com/v4/letter/m/73ab20/32.png) [@md2000](https://boards.straightdope.com/u/md2000)\ **Post date:** [October 18, 2013, 6:04pm UTC](https://boards.straightdope.com/t/why-does-evolution-look-so-directed/671280/67 "2013-10-18T18:04:43Z")
> [@](#): > > invaginations ? Word of the day… ---
**Author:** ![Skald\_the\_Rhymer](https://avatars.discourse-cdn.com/v4/letter/s/ecccb3/32.png) [@Skald\_the\_Rhymer](https://boards.straightdope.com/u/Skald_the_Rhymer)\ **Post date:** [October 18, 2013, 7:03pm UTC](https://boards.straightdope.com/t/why-does-evolution-look-so-directed/671280/68 "2013-10-18T19:03:56Z")
> [@md2000](#): > > > [@](#): > > > > invaginations > > ? Word of the day… From the Shorter Oxford English Dictionary: [QUOTE=seriously, I just answered that] invagination /0ɪnˌvadʒɪˈneɪʃ(ə)n/ noun. M17. [ORIGIN Modern Latin invaginatio(n-), formed as in-² + vagina: see -ation.] Orig., the action of sheathing something; esp. intussusception. Now usu., the folding in of a surface or membrane to form a hollow cavity or pouch; the cavity so formed. [/QUOTE] ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [October 19, 2013, 7:14am UTC](https://boards.straightdope.com/t/why-does-evolution-look-so-directed/671280/69 "2013-10-19T07:14:47Z")
> [@ZenBeam](#): > > [See Pharyngeal slit](http://en.wikipedia.org/wiki/Pharyngeal_slit) You quote part, and ignore all the places where it says “\*\*resembling \*\*gill slits” and “ **gill-like** slits”. By the time we get to your quote, I think there’s been sufficient qualification to indicate that the bare-bones phrase you bolded is not, in fact, the whole truth. > [@](#): > > :Here’s a page [Human embryos don’t have gill slits](http://evolutionwiki.org/wiki/Human_embryos_don't_have_gill_slits) on EvoWiki where people are arguing both for and against the term “gill slits”. The first response is particularly relevent: > I’m not going to argue semantics. You can call them what you like, but don’t say I’m wrong when I’m using a common term. I’m familiar with that page and the talk.origins discussion as well. - the relevant logical fallacy you’re going for there being “argumentum ad populum.” Suffice to say you and they are wrong - they _aren’t_ gill slits because they never connect to any gills. This is not just pedantry: calling them “gill slits” just puts ammunition in the hands of IDers who can easily point to the proven made-up recapitulation diagrams and accuse us of another scientific fraud _a-la_ Piltdown, and does nothing to indicate that we now know recapitulation theory is wrong. Which it absolutely is. ---
**Author:** ![njtt](https://avatars.discourse-cdn.com/v4/letter/n/ecd19e/32.png) [@njtt](https://boards.straightdope.com/u/njtt)\ **Post date:** [October 19, 2013, 7:46am UTC](https://boards.straightdope.com/t/why-does-evolution-look-so-directed/671280/70 "2013-10-19T07:46:51Z")
> [@Alan\_Smithee](#): > > **Ludwig Wittgenstein:** Why do people say it is natural to think that the sun revolves around the earth rather than the earth rotating around its own axis? > > **Elizabeth Anscombe:** Because it looks as though the sun revolves around the earth. > > **Ludwig Wittgenstein:** Fine, but then what would be like if it looked as if the earth rotates around its own axis? :rolleyes: Presumably we are supposed to think that Wittgenstein is the smart one here (and no doubt Anscombe, as one of his most faithful acolytes, thought so too). However, he ain’t. This is really just a demonstration of Wittgenstein’s literalism, and his tin ear for (and ignorance of) the historical. ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [October 19, 2013, 2:39pm UTC](https://boards.straightdope.com/t/why-does-evolution-look-so-directed/671280/71 "2013-10-19T14:39:25Z")
> [@MrDibble](#): > > You quote part, and ignore all the places where it says “\*\*resembling \*\*gill slits” and “ **gill-like** slits”. By the time we get to your quote, I think there’s been sufficient qualification to indicate that the bare-bones phrase you bolded is not, in fact, the whole truth.I’m familiar with that page and the talk.origins discussion as well. - the relevant logical fallacy you’re going for there being “argumentum ad populum.” Suffice to say you and they are wrong - they _aren’t_ gill slits because they never connect to any gills. This is not just pedantry: calling them “gill slits” just puts ammunition in the hands of IDers who can easily point to the proven made-up recapitulation diagrams and accuse us of another scientific fraud _a-la_ Piltdown, and does nothing to indicate that we now know recapitulation theory is wrong. Which it absolutely is. **Mr. Dibble** , I already told you I’m not interested in arguing semantics with you. You don’t like their usage of the term, that’s a problem you have with that community. And note that that _is_ a community page, not just the general population. As long as they are using that term, I am allowed to as well. _Get your own house in order._ Don’t come to me to complain about it. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [October 19, 2013, 4:39pm UTC](https://boards.straightdope.com/t/why-does-evolution-look-so-directed/671280/72 "2013-10-19T16:39:44Z")
> [@ZenBeam](#): > > **Mr. Dibble** , I already told you I’m not interested in arguing semantics with you. You don’t like their usage of the term, that’s a problem you have with that community. And note that that _is_ a community page, not just the general population. As long as they are using that term, I am allowed to as well. > > _Get your own house in order._ Don’t come to me to complain about it. It’s not semantics. The features are not correctly called gill slits, regardless if they are called that colloquially in some contexts. Neither Wikipedia or EvoWiki are authoritative sites. **Mr. Dibble** was quite correct to clarify your use of the term. Just because other people are misusing the term elsewhere doesn’t justify your misusing it here. ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [October 19, 2013, 5:48pm UTC](https://boards.straightdope.com/t/why-does-evolution-look-so-directed/671280/73 "2013-10-19T17:48:29Z")
It certainly is semantics. You’re not disputing that the features exist, you’re just complaining about the name. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [October 19, 2013, 6:13pm UTC](https://boards.straightdope.com/t/why-does-evolution-look-so-directed/671280/74 "2013-10-19T18:13:44Z")
> [@ZenBeam](#): > > It certainly is semantics. You’re not disputing that the features exist, you’re just complaining about the name. It’s an incorrect and ignorant usage that contributes to the misunderstanding of evolution, and so should best be avoided. **Mr. Dibble’s** clarification was entirely on target. I am not sure why you are continuing to defend the term. ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [October 19, 2013, 6:52pm UTC](https://boards.straightdope.com/t/why-does-evolution-look-so-directed/671280/75 "2013-10-19T18:52:13Z")
Because it’s not my fault that the term is in use. As I said, get your own house in order. ---
**Author:** ![Trinopus](https://avatars.discourse-cdn.com/v4/letter/t/2bfe46/32.png) [@Trinopus](https://boards.straightdope.com/u/Trinopus)\ **Post date:** [October 19, 2013, 7:47pm UTC](https://boards.straightdope.com/t/why-does-evolution-look-so-directed/671280/76 "2013-10-19T19:47:37Z")
Is recapitulation theory dead? I thought it had been scaled back, refined and reformed, brought up to date with advancing data, but that the basic principle is still sort of right. Fetal development goes through certain stages that resemble broad phases of evolutionary history. In the past, the theory was taken much too far, and used to try to make predictions and discoveries. Okay, that part is wrong. But isn’t there some validity remaining? ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [October 19, 2013, 8:16pm UTC](https://boards.straightdope.com/t/why-does-evolution-look-so-directed/671280/77 "2013-10-19T20:16:01Z")
> [@ZenBeam](#): > > Because it’s not my fault that the term is in use. As I said, get your own house in order. It’s your own fault if you insist on using a term that is incorrect after it has been pointed out. In any case, Wikipedia and EvoWiki are not “my house.” My house is GQ on the Straight Dope, and I’m trying to put it in order.😉 > [@Trinopus](#): > > Is recapitulation theory dead? I thought it had been scaled back, refined and reformed, brought up to date with advancing data, but that the basic principle is still sort of right. Fetal development goes through certain stages that resemble broad phases of evolutionary history. > > In the past, the theory was taken much too far, and used to try to make predictions and discoveries. Okay, that part is wrong. But isn’t there some validity remaining? Haekel’s [Recapitulation Theory](http://en.wikipedia.org/wiki/Recapitulation_theory), in which organisms go through embryonic stages that represent _adult_ stages of ancestors, and which is often characterized as “ontogeny recapitulates phylogeny,” is defunct and discredited. However, there are similarities between _embryonic_ stages of related organisms. This has been stated as “ontogeny recapitulates ontogeny.” > [@](#): > > The Haeckelian form of recapitulation theory is considered defunct.[23] However, embryos do undergo a period where their morphology is strongly shaped by their phylogenetic position, rather than selective pressures.[24] > > “Embryos do reflect the course of evolution, but that course is far more intricate and quirky than Haeckel claimed. Different parts of the same embryo can even evolve in different directions. As a result, the Biogenetic Law was abandoned, and its fall freed scientists to appreciate the full range of embryonic changes that evolution can produce—an appreciation that has yielded spectacular results in recent years as scientists have discovered some of the specific genes that control development.”[25] ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [October 19, 2013, 9:58pm UTC](https://boards.straightdope.com/t/why-does-evolution-look-so-directed/671280/78 "2013-10-19T21:58:48Z")
> [@Colibri](#): > > It’s your own fault if you insist on using a term that is incorrect after it has been pointed out. In any case, Wikipedia and EvoWiki are not “my house.” My house is GQ on the Straight Dope, and I’m trying to put it in order.😉 It’s not incorrect just because you don’t like it in GQ. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [October 19, 2013, 10:07pm UTC](https://boards.straightdope.com/t/why-does-evolution-look-so-directed/671280/79 "2013-10-19T22:07:59Z")
> [@ZenBeam](#): > > It’s not incorrect just because you don’t like it in GQ. **Moderating** It’s incorrect because it’s incorrect, not because I don’t like it. But at this point, this has become a hijack. Let’s drop it. Colibri General Questions Moderator [Previous page](https://boards.straightdope.com/t/why-does-evolution-look-so-directed/671280.md?page=3)