# How on earth did \*that\* evolve? **URL:** \ **Category:** Great Debates\ **Created:** [June 18, 2004, 7:19am UTC](https://boards.straightdope.com/t/how-on-earth-did-that-evolve/251009 "2004-06-18T07:19:13Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Zagadka](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zagadka/32/7272_2.png) [@Zagadka](https://boards.straightdope.com/u/Zagadka)\ **Post date:** [June 18, 2004, 4:55pm UTC](https://boards.straightdope.com/t/how-on-earth-did-that-evolve/251009/21 "2004-06-18T16:55:21Z")
> [@astro](#): > > 1: Many fish _already_ have a very well developed ability to employ narrowly directed, targeted streams of water precisely where they wish at varying pressures levels underwater. This is used, among other things, for stunning or routing small prey. This whole thing brought up another question. Why can humans spit? The answer, of course, is that nothing evolved to spit, it evolved so it could spit, and the useful trait encouraged greater survivability. It is a bit like asking, “why did the human hand evolve to hold a gun so well” - it didn’t, the function came after the form. > [@](#): > > 2: Fish eyesight is not that bad at or near the surface as many a frustrated fisherman can attest. Nothing surprising here, being able to see above the surface is a useful trait - seeing bugs, or even predators. In this case… I have a question though. Is the behavior innate, or is it “taught”? ---
**Author:** ![Polerius](https://avatars.discourse-cdn.com/v4/letter/p/d78d45/32.png) [@Polerius](https://boards.straightdope.com/u/Polerius)\ **Post date:** [June 18, 2004, 6:24pm UTC](https://boards.straightdope.com/t/how-on-earth-did-that-evolve/251009/22 "2004-06-18T18:24:21Z")
> [@sevastopol](#): > > My guess is the spitting came about as a modification of common fish “foraging” behaviour. That is, disturbing the riverbeds to unearth buried food. Lots of fish do this currently. > [@astro](#): > > 1: Many fish already have a very well developed ability to employ narrowly directed, targeted streams of water precisely where they wish at varying pressures levels underwater. This is used, among other things, for stunning or routing small prey. Great! These are the types of answers I was looking for. I didn’t know that many fish had this ability underwater. Thanks. As an aside, to people who keep bringing God up, my interest in this was akin to seeing a model ship inside a bottle and wondering “how the hell did they get that in there?” I don’t assume God put it in there just because I can’t figure it out at the moment. I just saw this fish on TV and got curious about the way in which it evolved, and I thought some Dopers who know more about evolution and/or fish would suggest a reasonable mechanism, which \*\*sevastopol \*\* and \*\*astro \*\* did. ---
**Author:** ![Cuckoorex](https://avatars.discourse-cdn.com/v4/letter/c/ad7895/32.png) [@Cuckoorex](https://boards.straightdope.com/u/Cuckoorex)\ **Post date:** [June 18, 2004, 11:03pm UTC](https://boards.straightdope.com/t/how-on-earth-did-that-evolve/251009/23 "2004-06-18T23:03:18Z")
I always wondered about the evolution of the Horned Toad’s defense mechanism of squirting blood from its eyes…I mean, _damn_. ---
**Author:** ![Shade](https://avatars.discourse-cdn.com/v4/letter/s/2bfe46/32.png) [@Shade](https://boards.straightdope.com/u/Shade)\ **Post date:** [June 19, 2004, 12:04am UTC](https://boards.straightdope.com/t/how-on-earth-did-that-evolve/251009/24 "2004-06-19T00:04:08Z")
> [@Polerius](#): > > Great! These are the types of answers I was looking for. I didn’t know that many fish had this ability underwater. Thanks. > > As an aside, to people who keep bringing God up, my interest in this was akin to seeing a model ship inside a bottle and wondering “how the hell did they get that in there?” I don’t assume God put it in there just because I can’t figure it out at the moment. I read your OP again. I’m sorry, I got caught up in a philosophical hijack when I shouldn’t have been. This really should have been about interesting evolutions. The jetting-underwater was fascinating. OK, my list of “wow, how did that evolve” Eyes. (I know, I know, but it is amazing) Insects that navigate by the sun. Intellegence. Sexual reproduction. ---
**Author:** ![bodswood](https://avatars.discourse-cdn.com/v4/letter/b/e68b1a/32.png) [@bodswood](https://boards.straightdope.com/u/bodswood)\ **Post date:** [June 19, 2004, 3:02am UTC](https://boards.straightdope.com/t/how-on-earth-did-that-evolve/251009/25 "2004-06-19T03:02:57Z")
Mangetout, you quoted Charles Darwin as follows: > [@](#): > > “To suppose that the eye with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest degree…” and note that he goes on to immediately answer this apparent absurdity. Since you have the cite at hand, could you give his answer? ---
**Author:** ![MEBuckner](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mebuckner/32/2896_2.png) [@MEBuckner](https://boards.straightdope.com/u/MEBuckner)\ **Post date:** [June 19, 2004, 3:52am UTC](https://boards.straightdope.com/t/how-on-earth-did-that-evolve/251009/26 "2004-06-19T03:52:31Z")
[_Origin of Species_](http://www.bartleby.com/11/), Section VI (“Difficulties of the Theory”), [Organs of Extreme Perfection and Complication](http://www.bartleby.com/11/6004.html). ---
**Author:** ![bodswood](https://avatars.discourse-cdn.com/v4/letter/b/e68b1a/32.png) [@bodswood](https://boards.straightdope.com/u/bodswood)\ **Post date:** [June 19, 2004, 4:22am UTC](https://boards.straightdope.com/t/how-on-earth-did-that-evolve/251009/27 "2004-06-19T04:22:22Z")
Thanks, M.E.! Here are the two immediate paragraphs in question for easy viewing: > [@](#): > > To suppose that the eye with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest degree. When it was first said that the sun stood still and the world turned round, the common sense of mankind declared the doctrine false; but the old saying of Vox populi, vox Dei, as every philosopher knows, cannot be trusted in science. Reason tells me, that if numerous gradations from a simple and imperfect eye to one complex and perfect can be shown to exist, each grade being useful to its possessor, as is certainly the case; if further, the eye ever varies and the variations be inherited, as is likewise certainly the case and if such variations should be useful to any animal under changing conditions of life, then the difficulty of believing that a perfect and complex eye could be formed by natural selection, though insuperable by our imagination, should not be considered as subversive of the theory. How a nerve comes to be sensitive to light, hardly concerns us more than how life itself originated; but I may remark that, as some of the lowest organisms, in which nerves cannot be detected, are capable of perceiving light, it does not seem impossible that certain sensitive elements in their sarcode should become aggregated and developed into nerves, endowed with this special sensibility. > > In searching for the gradations through which an organ in any species has been perfected, we ought to look exclusively to its lineal progenitors; but this is scarcely ever possible, and we are forced to look to other species and genera of the same group, that is to the collateral descendants from the same parent-form, in order to see what gradations are possible, and for the chance of some gradations having been transmitted in an unaltered or little altered condition. But the state of the same organ in distinct classes may incidentally throw light on the steps by which it has been perfected. The juxtaposition (perhaps even possible correlation) by Darwin of abiogenesis and evolution in “how a nerve comes to be sensitive to light, hardly concerns us more than how life itself originated” is I guess understandable given that how the eye works was beyond 19th century science. ---
**Author:** ![Dunderman](https://avatars.discourse-cdn.com/v4/letter/d/ecb155/32.png) [@Dunderman](https://boards.straightdope.com/u/Dunderman)\ **Post date:** [June 19, 2004, 11:01am UTC](https://boards.straightdope.com/t/how-on-earth-did-that-evolve/251009/28 "2004-06-19T11:01:13Z")
> [@Shade](#): > > Intellegence. This I can’t see at all. Of all the traits created by evolution, I think intelligence is among the easiest to understand. Even a small increase in intelligence is an evolutionary advantage, especially for a social animal. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [June 20, 2004, 1:11am UTC](https://boards.straightdope.com/t/how-on-earth-did-that-evolve/251009/29 "2004-06-20T01:11:19Z")
> [@bodswood](#): > > Mangetout, you quoted Charles Darwin… Since you have the cite at hand, could you give his answer? Sure: > [@Charles Darwin](#): > > Organs of extreme Perfection and Complication. > To suppose that the eye with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest degree. When it was first said that the sun stood still and the world turned round, the common sense of mankind declared the doctrine false; but the old saying of Vox populi, vox Dei, as every philosopher knows, cannot be trusted in science. Reason tells me, that if numerous gradations from a simple and imperfect eye to one complex and perfect can be shown to exist, each grade being useful to its possessor, as is certainly the case; if further, the eye ever varies and the variations be inherited, as is likewise certainly the case and if such variations should be useful to any animal under changing conditions of life, then the difficulty of believing that a perfect and complex eye could be formed by natural selection, though insuperable by our imagination, should not be considered as subversive of the theory. How a nerve comes to be sensitive to light, hardly concerns us more than how life itself originated; but I may remark that, as some of the lowest organisms, in which nerves cannot be detected, are capable of perceiving light, it does not seem impossible that certain sensitive elements in their sarcode should become aggregated and developed into nerves, endowed with this special sensibility. There is more still (pages and pages of it), but in this short follow-on, not only does he speculate on possible pathways and note that the idea of irreducible complexity is destroyed if a continuum of examples of _reduced_ complexity can be found, but he also tags the opening objection as an argument from ignorance. ---
**Author:** ![bodswood](https://avatars.discourse-cdn.com/v4/letter/b/e68b1a/32.png) [@bodswood](https://boards.straightdope.com/u/bodswood)\ **Post date:** [June 21, 2004, 1:55am UTC](https://boards.straightdope.com/t/how-on-earth-did-that-evolve/251009/30 "2004-06-21T01:55:20Z")
“There is more still (pages and pages of it), but in this short follow-on, not only does he speculate on possible pathways and note that the idea of irreducible complexity is destroyed if a continuum of examples of reduced complexity can be found.” Keywords: ‘speculate’ and ‘if’. “[Darwin] also tags the opening objection as an argument from ignorance” Ah! I never would have guessed! Very Socratic of him. ---
**Author:** ![Darwins\_Finch](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darwins_finch/32/20304_2.png) [@Darwins\_Finch](https://boards.straightdope.com/u/Darwins_Finch)\ **Post date:** [June 21, 2004, 2:23am UTC](https://boards.straightdope.com/t/how-on-earth-did-that-evolve/251009/31 "2004-06-21T02:23:26Z")
> [@bodswood](#): > > Keywords: ‘speculate’ and ‘if’. Those are, however, very important keywords, as the primary keyword for ID is “can’t” - “it _can’t_ have evolved through intermediate steps, therefore it must have been designed.” If it can be shown that, yes, it _could have_ evolved through some intermediates, even if those intermediates are not now manifest, then that is sufficient to counter ID’s at-least-as-speculative “can’t”. ---
**Author:** ![bodswood](https://avatars.discourse-cdn.com/v4/letter/b/e68b1a/32.png) [@bodswood](https://boards.straightdope.com/u/bodswood)\ **Post date:** [June 21, 2004, 3:28am UTC](https://boards.straightdope.com/t/how-on-earth-did-that-evolve/251009/32 "2004-06-21T03:28:20Z")
Agree, finch. Can I call you lot the “Not-now-manifests”?! Does seem to be a recurring theme… ---
**Author:** ![emekthian](https://avatars.discourse-cdn.com/v4/letter/e/ecae2f/32.png) [@emekthian](https://boards.straightdope.com/u/emekthian)\ **Post date:** [June 21, 2004, 4:46am UTC](https://boards.straightdope.com/t/how-on-earth-did-that-evolve/251009/33 "2004-06-21T04:46:34Z")
I’ve always wondered how species evolved into other species with a greater or lesser number of chromosomes. ---
**Author:** ![Darwins\_Finch](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darwins_finch/32/20304_2.png) [@Darwins\_Finch](https://boards.straightdope.com/u/Darwins_Finch)\ **Post date:** [June 21, 2004, 4:52am UTC](https://boards.straightdope.com/t/how-on-earth-did-that-evolve/251009/34 "2004-06-21T04:52:50Z")
> [@bodswood](#): > > Can I call you lot the “Not-now-manifests”?! Does seem to be a recurring theme… I’m not sure that would be an accurate descriptor, really. Many of the proposed intermediates have been identified, in one form or another, in a variety of organisms (eyes, for example - there are a large number of different “eyes” out there in the animal world, covering virtually all ground between “light-sensitive nerve” to “vertebrate eye”. And there are other eyes which work just as well as our own, if not better, despite having evolved along separate paths). And, many other intermediates can be found in the fossil record. That is primarily what I meant by “not now manifest” - the intermediates are long dead, but not necessarily unknown to us. Even though a good many of the answers to the question “how did _this_ evolve?” are speculative, they do nevertheless form a hypothesis to start from. If suitable intermediates can be discovered or identified, then that lends support to the proposed pathway. If none are found, then the proposed pathway is necessarily weaker for it, and other pathways should probably be examined. **emekthian** : take a look [here](http://www.umanitoba.ca/afs/plant_science/COURSES/CYTO/l24/l24.1.html) for some plant examples (and explanations). ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [June 21, 2004, 7:43am UTC](https://boards.straightdope.com/t/how-on-earth-did-that-evolve/251009/35 "2004-06-21T07:43:19Z")
> [@bodswood](#): > > Keywords: ‘speculate’ and ‘if’. The word ‘if’ doesn’t always imply blind specualtion; You could actually replace it with ‘since’ in this particular context, thus: _the idea of irreducible complexity is destroyed **since** a continuum of examples of reduced complexity can be found._ Didn’t someone here once formulate a law of debate about arguments degenerating into linguistic nitpicks? ---
**Author:** ![bodswood](https://avatars.discourse-cdn.com/v4/letter/b/e68b1a/32.png) [@bodswood](https://boards.straightdope.com/u/bodswood)\ **Post date:** [June 21, 2004, 7:56am UTC](https://boards.straightdope.com/t/how-on-earth-did-that-evolve/251009/36 "2004-06-21T07:56:50Z")
But one person’s nitpick is another person’s scholarly passion for accuracy! Not to mention that Darwin’s ideas in the Chapter cited are better rendered by hypothetical ‘if’ than by causal ‘since’. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [June 21, 2004, 10:24am UTC](https://boards.straightdope.com/t/how-on-earth-did-that-evolve/251009/37 "2004-06-21T10:24:38Z")
Indeed, but this particular ‘if’ was mine, not Chuck’s. ---
**Author:** ![tdn](https://avatars.discourse-cdn.com/v4/letter/t/94ad74/32.png) [@tdn](https://boards.straightdope.com/u/tdn)\ **Post date:** [June 21, 2004, 4:48pm UTC](https://boards.straightdope.com/t/how-on-earth-did-that-evolve/251009/38 "2004-06-21T16:48:16Z")
OK, what about the porcupine, what with its ability to fire projectiles? The electric eel? The venus fly trap? ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [June 21, 2004, 5:26pm UTC](https://boards.straightdope.com/t/how-on-earth-did-that-evolve/251009/39 "2004-06-21T17:26:44Z")
> [@emekthian](#): > > I’ve always wondered how species evolved into other species with a greater or lesser number of chromosomes. Chromosomal splitting and/or fusing is not unusual at all. Additionally, populations of similar organisms\* with differing chromosomal counts are not automatically unable to breed. Is there some reason you thought that mechanism was particularly strange? \*I’m purposely not useing the term “species” here as these populations may or may not be different species. ---
**Author:** ![Papermache\_Prince](https://avatars.discourse-cdn.com/v4/letter/p/f05b48/32.png) [@Papermache\_Prince](https://boards.straightdope.com/u/Papermache_Prince)\ **Post date:** [June 21, 2004, 5:36pm UTC](https://boards.straightdope.com/t/how-on-earth-did-that-evolve/251009/40 "2004-06-21T17:36:18Z")
Porcupines do not fire projectiles. [BBC Porcupine page](http://www.bbc.co.uk/nature/wildfacts/factfiles/607.shtml) - “They cannot throw their quills like spears as folklore suggests.” [Previous page](https://boards.straightdope.com/t/how-on-earth-did-that-evolve/251009.md?page=1) [Next page](https://boards.straightdope.com/t/how-on-earth-did-that-evolve/251009.md?page=3)