Talk:Exaptation

Revision

Starting with the intent to edit this article (per early spring 07), I ended up completely revising it. The original article lacked references and headings. Besides including those, I inserted two examples that would be understandable to a lay audience (e.g., high school students). The process of exaptation helps to explain why living organisms sometimes appear jury-rigged, as is now explained. (Related articles—preadaptation, co-option, and evolutionary psychology—will point to this article.)

Hopefully, the new structure of this article will facilitate other scholars correcting my errors & improving upon my content. (I see that TimVickers w/ a biochem background has recently improved this article. I look forward to his improvements on my changes.) W Pete Welch 01:01, 6 June 2007 (UTC)W Pete Welch

Merge

Should preadaptation not be merged with this? I was originally going to propose that it be merged into adaptation, but then found this much larger article. Richard001 10:44, 14 August 2007 (UTC)

That seems very appropriate. I'd support that.--Talionis ^{(Shout me · Stalk me)} 09:51, 11 October 2007 (UTC)

Submerged in it, yes.m Midgley (talk) 02:08, 24 August 2008 (UTC)

Agree that they should be merged, but under which heading - if preadaptation has priority, are we junking it just because Gould found the expression annoying? What is the current most common usage amongst biologists?Palindromia (talk) 13:47, 21 September 2008 (UTC)

I did some poking around, and both are used in scientific literature (recent and total) at approximately the same frequency, so there's no clear basis for preference on that count. Personally, I like "exaptation" more, because, to the average reader, "preadaptation" sounds little wonky. Plus, on the effort side, exaptation is longer, so it'd be easier to merge the other article to this one than the other way around. And, IMHO, it just sounds cooler. Mokele (talk) 14:40, 21 September 2008 (UTC)

• oppose These are different concepts, e.g.
  • Arthropods were well pre-adapted to colonise land, because their existing jointed exoskeletons provided protection against dessication, support against gravity and a means of locomotion that was not dependent on water.
  • Molluscs exapt like crazy - a lot of their internal organs perform 2 apparently unrelated functions. -- Philcha (talk)

• oppose There are instances where the word preadaptation, including the apparent foresight, are justified. I edited the preadaptation page to discuss these, include both my own work and that of Ilan Eshel. Joannamasel (talk) 15:59, 22 August 2010 (UTC)

Neither of the papers cited at the end of preadaptation give any support to "foresight". That marginal habitats *may* resemble future habitats is luck, not foresight - more often than not it's probably false (unless you simply define "marginal" as "anything less than optimal", in which case that's a logical fallacy called begging the question). And the level of deleterious mutations floating around in cryptic diversity is similarly irrelevant, because whether that diversity proves useful or not is also nothing more than luck. Not to mention that there's no plausible mechanism. Mokele (talk) 02:16, 23 August 2010 (UTC)

As discussed by Eshel and Matessi, climate change that does NOT resemble a previous environment, encountered only rarely or at the spatial margins, would be rather unusual. There is no luck involved here. Nor is there foresight. There is a correlation, but this is enough for the result. And as discussed in my own paper, cryptic lethals are hardly irrelevant to adaptation. If an organism has one, the organism's genotype is not adaptive, irrespective of the environment. There are many mutations, eg loss of a very basic function, where we can clearly predict that no environment will be encountered where that is adaptive, while other mutations, eg change in a quantitative trait, where while the direction of the environment is unpredictable, the fact is clear that this mutation falls in a class with the potential for adaptation. In any case, both cited papers are published in leading journals in the field. I have never seen any rebuttal of their arguments in the scientific literature. The default in this discussion should be to accept that the citations support the claim made, since this is clearly what these papers in question say. It would be more appropriate to go on to cite references that dissent than to delete these citations, which are both clearly on-topic.Joannamasel (talk) 02:40, 23 August 2010 (UTC)

That future climate may resemble current marginal climate is NOT simply a given - what makes an area marginal may have more to do with nesting sites, predator populations, local competitions, or nothing more than distance from foraging grounds in many species. Never mind that a species range may include MULTIPLE marginal climate-habitats which are marginal for different and often opposite reasons (too hot to the south, too cold to the north, too wet to the east, too dry to the south, etc.) and only one of these combinations (if any) will play out in future change.

Eshel and Matessi included this possibility in their model. They looked at a quantitative trait, with either of the two extremes equally likely to be the direction of the environmental change.

That's not really sufficient - any given habitat is defined by *dozens* of variables, and the future condition may not be represented within a species range. It also falsely assumes that the species range, including marginal habitat, corresponds to the actual physiological tolerances of the species, which we know is untrue in many, many cases. There is still no evidence that it amounts to anything more than "Populations adapt to a variety of conditions in their range, and sometimes by dumb luck one of these will resemble the future". It's still not even slightly predictive in any way, shape or form. Mokele (talk) 04:07, 23 August 2010 (UTC)

Plus, things *can* change beyond the conditions in a species range, and frequently do - just ask the dinosaurs. And your paper demonstrates (as much as model can do) that a potentially useful occurrence can happen, that's all - there's no guarantee that any of the cryptic variation will be useful at all, nor that it's any more likely to be helpful.

No, there is no guarantee. That's why I referred to probabilistic statements. Continuous environmental change is not the only possibility, but it is the most common one.

I'd dispute that it's the most common - the history of earth is replete with examples of massive environmental change, whether due to asteroids or species invasions. Hell, even within the last three million years alone there have been numerous ice ages, massive changes in sea level, a union of continents that resulted in the near-total extinction of the South American fauna, and the origin of the most environmentally destructive species ever. But even still, it's no more probabilistic than if all humans shorter than 6'5" died from some mystery cause - no foresight was involved, just a species with genetic variability. Plus, we'll "remember" the hits (they survive) and "forget" the misses (they go extinct). I'm not saying it's not real; I'm saying it's so distantly and weakly related to pre-adaptation that it doesn't belong in the article. Mokele (talk) 04:07, 23 August 2010 (UTC)

My problem is that the way you phrase your edit suggests a weak form of foresight, which is simply not true. All you have is dumb luck (adapting to the right marginal habitat) and a potential quirk of genetics that *might* make things easier in a completely non-directed way.

I'm not saying the papers are wrong, I'm saying that what they show is not foresight, probabilistic direction, or anything even close, and that to include them with the current phrasing is misleading at best. Mokele (talk) 03:13, 23 August 2010 (UTC)

I have weakened the language in several places, including making it clear that the preadaptation of cryptic genetic variation is relative to the adaptive potential of a defined alternative.Joannamasel (talk) 03:45, 23 August 2010 (UTC)

Given the context of the article, though, it still doesn't belong. Yes, a genome where lethal alleles have been purged from cryptic variation would be more likely to contain adaptations, but that's not the same thing as foresight or even probabilistic planning. Because it should either happen in all species (if your model is right) or none of them (if your model is wrong). Either way, it's not planning, foresight, or anything - it's just something that happens, and that it's helpful when change rolls around. That's like saying mutation itself is a form of preadaptation, as it lays the genetic groundwork and variation that will be selected upon - it's taking the term too far, and applying pre-adaptation to anything that affects the future at all. Mokele (talk) 04:07, 23 August 2010 (UTC)

You are welcome to disagree, thinking that we should have chosen a different word for these phenomena. I didn't start it, I followed Ilan Eshel's lead, and maybe it was a mistake. But the word is out there with this definition now, so I think the page should cover alternative definitions in the scientific literature of its title word. It's absolutely not the same thing as foresight, and if you think this isn't clear from the current text, please edit it until it is. Nor is it "planning", but it is a probabilistic future-oriented statement, with reference to an alternative. —Preceding unsigned comment added by Joannamasel (talk • contribs) 14:42, 23 August 2010 (UTC)

I've given it a shot, separating it into a paragraph that addresses the overlooked point that just because something looks like foresight doesn't mean it is (which I think is a bit more in keeping with the somewhat elementary level of the page). Mokele (talk) 14:54, 23 August 2010 (UTC)

Great! But I still oppose merging the preadaptation and exaptation pages, because of this material.Joannamasel (talk) 15:37, 23 August 2010 (UTC)

I have not followed this article in any detail, but the current lead needs work because it fails to give any clue regarding what exaptation is. I suppose it would be hard to briefly describe the situation without sounding somewhat mystical, but we need to try. Johnuniq (talk) 02:02, 24 August 2010 (UTC)

Remove Controversy Section?

I'm proposing the controversy section be removed, for the simple reason that it's *not* a controversy about exaptation, but a controversy caused by the possibility of exaptation. The concept of exaptation isn't controversial at all, AFAIK. The text in the controversy section should be a part of the article of evolutionary psychology instead, and does in fact appear (in reduced form) in the controversies page of that discipline. Plus, stylistically, it just seems to come out of left field and take up an unusually large proportion of the page given the only tangential relevance to exaptation as a whole. Mokele (talk) 03:53, 26 February 2008 (UTC)

Instead of removing, I think the criticism section should be given proper context, which arguably it now has. I would consider myself a member of the "lay" audience, and the reason I looked up exaptation was to understand the "evolution wars" arguments. If there was no criticism section at all, I would not have found what I was looking for. On ther other hand, without the proper context, I wouldn't have been properly informed as to what elements of the exaptation concept are widely accepted, and which parts (or perhaps extrapolations of the theory) are still under debate. I think wiki should serve multiple audiences, and so far, this article does the job for me.72.92.17.240 (talk) 20:42, 16 April 2008 (UTC)

What, exactly, did you get out of the controversy section, though? IMHO, it is far too specific; pertaining to one argument about one field. I was thinking the article would be better served by relocating the current section to the page on controversies about evolutionary psychology and replacing it with three sections currently lacking: one with a list of examples (accompanied by short explanations), another with difficulties and issues in identifying a trait as an exaptation, and finally a section on the implications of exaptation to evolutionary thought. Would this serve the same purpose from your POV? Mokele (talk) 01:14, 17 April 2008 (UTC)

I found the physical / social pain interesting - nervous systems, like most evolved features, are imperfect but "good enough" (other examples of this include included referred pain and ghost limbs).

I'm not sure about feathers originating as thermoregulation (the Mesozoic was a good deal warmer than modern climates) and there's at least one alternative hypothesis, that feathers originated as display devices (see Origin of birds for details) - but whichever is right, feathers are great a "threefer" example of exaptation.

Another striking example is that arthropods were apparently the first animals to colonise land, and their jointed exoskeltons gave them a head start in dealing with the challenges of gravity and dessication (see Evolutionary history of life). --Philcha (talk) 11:01, 6 March 2009 (UTC)

Making assumptions?

"Bird feathers are a classic example: initially these evolved for temperature regulation, but later were adapted for flight." We know this for a fact, do we? I'd suggest either adding something like "It is believed..." in there, or giving some reference to verify this. It just seems hard to say factually that we know why a creature originally developed some feature. 192.91.171.36 (talk) 17:07, 20 May 2009 (UTC)

Mergefrom Preadaptation

Restarting the previous discussion. The article currently says that Exaptation is the currently preferred term for what used to be known as Preadaptation because that name could give a false impression of teleology. Otherwise, despite such a distinction, they seem close enough to meaning the same thing that the Preadaptation article should just become a redirect to this article. WikiDao ☯ (talk) 19:41, 13 November 2010 (UTC)

Another phrase I'm seeing is 'cryptic (genetic) variation', which as far as I understand is an example of exaptation? I've requested a 'cryptic variation' article, but I agree it'd be helpful to bring these terms together (w/REDIRECTs) (and possibly a tie-in with Cryptic species complex) to help readers better understand this frontier of EvBio. Twang (talk) 20:42, 3 June 2011 (UTC)

Support per OP reasoning. That's what I see in the literature. – Maky ^« talk » 07:34, 10 March 2012 (UTC)

Not an exception, but the rule?

Isn't it a general principle that in evolution, new traits appear before evolution acts on them, rather than new traits being developped in response to new circumstances? Traditionally taught portrayals still give the impression that life-forms encounter new circumstances, and subsequently adapt, which is absurd and often patently impossible. Instead, the natural variation in a population includes already existing individuals with traits that happen to be useful in the new circumstances or environment, completely incidentally. For example, the account in the preadaptation article regarding the flatter feet of humans is still misleading: Flatter feet did not develop in humans as a reaction or even for the purpose to squat, instead some populations happened to develop flatter feet and this trait proved advantageous by allowing new sources of food to be exploited. Evolution is always driven by chance, by serendipity – though self-reinforcing, at least in traits which allow gradual rather than discrete (yes/no, A/B/C) distinctions: Once a trait, such as flatter feet or a longer neck in a giraffe, has proved advantageous, an even more pronounced or exaggerated version of the same trait can occur, and the expression of the trait can escalate up to a point where it ceases to be advantageous, or the cost/benefit ratio turns negative. --Florian Blaschke (talk) 16:24, 13 November 2011 (UTC)

Yes, but "exaptation" is still more specific, in that the trait must not only be pre-existing, but that a change in function must occur. Consider an example (which I just fixed) from the article. Early fish, by random mutation, gained a small outcropping of the pharynx which could be used to hold air, and via selection, this became the lungs which are widespread in both modern primitive fish and terrestrial vertebrates ("traditional" evolution). Subsequently, the already-developed lungs were employed for a different purpose, buoyancy control, in more "advanced" fish, and selection took off in a new direction, changing the organ's function (exaptation). So it's not so much about whether the initial trait occured in response to the environment, but rather whether a functional shift occurred during the evolution to the current form.

Also, as a side-note, traits developing in response to the environment isn't so farfetched - phenotypic plasticity apparently interacts with evolution in interesting and complex ways that we're just beginning to understand. Unfortunately, I lack the expertise the explain further, but there are several books out on the subject, if you're interested. Mokele (talk) 16:53, 13 November 2011 (UTC)

Theory of Reasoning Example

I made a one-word change to this example (added "putatively") to clarify that the status of rationality as an exaptation is an assumption of the theory, not necessarily accepted as a behavioral adaptation "to seek truth" by a majority of workers; the evolution of the ability to reason is probably up for considerable debate. My original edit was a deletion of this entire paragraph, as I have major reservations about this example, both because it is a questionable example of an exaptation, and because the cited article gives me the impression that it is either not a useful summary of the theory and debate on it, or that the scholarship of the cited researchers on evolution and adaptation is lacking. I am inclined to give the researchers the benefit of the doubt, but additional, primary sources would be an improvement. Another concern is that, though the current writing does acknowledge that this is a controversial example, I think that including relatively unverified and controversial examples when there are only two other clear examples may cause confusion. -colbyg --- — Preceding unsigned comment added by 160.129.141.175 (talk) 15:06, 9 January 2012 (UTC)

Merge from Co-option (biology)

The following discussion is closed. Please do not modify it. Subsequent comments should be made in a new section. A summary of the conclusions reached follows.

The result of this discussion was no merge,

---

Merge from Co-option (biology): Widefox (talk) 12:40, 26 March 2012 (UTC)

Oppose - These are two totally different concepts. Co-option is one organism hijacking the metabolism of another at an individual level on short timescales, exaptation is a single organism re-purposing one part of its own biology over evolutionary time. HCA (talk) 18:30, 27 March 2012 (UTC)

The above description of co-option ("one organism hijacking the metabolism of another at an individual level on short timescales") is incorrect. This may be an example of co-option, but it is not the definition. Co-option, exaptation and preadaptation are related as follows. Exaptation and preadatation are different words for the same event: When an existing trait is co-opted to take on a new functional use during the course of evolution. So exaptation is a noun - it is the event of functional shift, and co-option is a verb - it describes the process of functional shift. See Gene co-option in morphological evolution for a definition of co-option. — Preceding unsigned comment added by 174.16.78.84 (talk) 15:26, 26 December 2012 (UTC)

Oppose/Comment - The content at "Co-option (biology)" does not seem to be describing evolutionary co-option, but rather "the capacity of intracellular parasites to use host-cell proteins to complete their vital cycle". Since this term may also be used to refer to evolutionary co-option, I suggest that "Co-option (biology)" be moved to "Cooption (microbiology)" or something like that. Then "Co-option (biology)" could either redirect to "Exaptation" or become a disambiguation page. 138.16.160.4 (talk) 21:13, 13 August 2012 (UTC)

Oppose - and remember there is a growing non-biological use of the term

The discussion above is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.

Spandrel

Spandrel (biology) implies that "spandrel" in the sense of evolutionary biology can be used synonymously with "exaptation", but "spandrel" is not even mentioned in this article ... what gives? Another related article, or possibly even merge candidate? --Florian Blaschke (talk) 23:22, 1 October 2012 (UTC)

While a spandrel *could* be later exapted, the two are not necessarily the same. Plenty of spandrels remain non-adaptive, and plenty of exaptations have non-spandrel origins. HCA (talk) 02:04, 2 October 2012 (UTC)

Hands

Would not tool use be a form of exaptation? Originally to improve the range of sizes and locations of branches reachable, then co-opted to manipulate objects. Not necessarily human-exclusive either, can be seen with Chimpanzees, Orang-utans, and various primates. 218.212.228.206 (talk) 06:46, 3 November 2012 (UTC)

Teleology contrary to basic principle of natural selection?

I tend to disagree with the emphasized portion of this sentence: "For many years the phenomenon was labeled "preadaptation," but since this term suggests teleology, which is contrary to a basic principle of natural selection, it has been replaced by other terms in the years after Darwin."

Teleology does not contradict natural selection. For example: If we were able to teleologically modify an organism so that it's life span increased, or some other highly selective phenotype change, natural selection could still then act to fixate that modification in the rest of the population. Instead of "natural selection", better phrases might be:

• standard evolutionary theory
• natural evolution
• neo-Darwinian evoluion
• the modern evolutionary synthesis

But your example isn't teleology in natural selection, as the teleology is introduced by *artificial* means, and natural selection subsequently acts on the variability introduced by artificial means. The statement as it current stands is 100% accurate - natural selection only acts on *existing* variability in response to *existing* selective pressure. There is no mechanism allowing "anticipation or planning for the future", including deliberate preservation of a currently deleterious or useless trait for future use - that requires human intervention, in the form of artificial selection (or genetic modification). HCA (talk) 14:53, 18 July 2013 (UTC)

Inconsistency about feathers

In the lead we say that their origins may be in thermal regulation. But in the "examples" section, we say that they [definitely] are. I don't know whether that question is settled or not, but this article ought to take a single consistent stance (I suppose one of is, may be, and jury's-still-out).—PaulTanenbaum (talk) 12:58, 12 September 2013 (UTC)

Adding other examples

I have found a couple primary sources pointing to evidence of exaptations that haven't been listed in the article yet. These include the human hand/fist as it came about as a "tag-along" trait that wasn't a target of natural selection. Metabolic systems may be another example of an exaptation because of the many possibilities for innovation based off of their ability to use many carbon products as viable carbon derivatives sufficient for metabolism. I will add these examples and in-depth information in due time.

Go for it, but we should be careful the article doesn't devolve (hehehe) into a "listicle". HCA (talk) 14:02, 1 October 2014 (UTC)

Additional information to "Preadaptation" section

I would like to add a few sentences to the "Preadaptation" section that will help better define exaptation and make it slightly more understandable. I feel it is a complex topic in evolutionary biology that isn't the easiest to understand for most people. — Preceding unsigned comment added by Mikhaylyuk.1 (talk • contribs) 03:08, 1 October 2014 (UTC)

Wolf "behavioral" example

I feel as though some more evidence is required concerning the wolf behavior example - also, can behaviors be considered as exaptations? I somewhat understand the idea behind this example; however, I'm not totally convinced about it. — Preceding unsigned comment added by Mikhaylyuk.1 (talk • contribs) 04:18, 1 October 2014 (UTC)

Well, a trait's a trait, so I'm not sure why behavior should be excluded. That said, I'm also skeptical of this particular example, especially since wild wolf packs are basically family units, with the so-called "alpha pair" simply being the mother and father of the rest of the pack (who stay until they're old enough to leave and try to start breeding themselves). It could be considered an exaptation, but its the same behavior being used by the same individuals across time, though admittedly for a different purpose. If we can find a stronger example, that might be better. Perhaps Wing-assisted_incline_running? There's a mechanical component, sure, but there's also the idea of coopting the flapping behavior. Or something else? HCA (talk) 14:32, 1 October 2014 (UTC)

Ok, I understand the reasoning behind "a trait's a trait" and that behavior could surely be considered as such; however, I agree with your reasoning and conclusion that there could be a better example for a behavioral exaptation. I personally haven't come across any behavioral examples but would be interested in seeing one if someone does manage to find it. To me, exaptation revolves more around certain behavior (physically) that as compared to behavioral because of the complexity of behaviors in comparison to action/function (with reason). I am wondering about your reasoning behind having Wing-assisted incline running as an exaptation... Could you elaborate? Do you mean using wings for something that they weren't originally meant for or..? — Preceding unsigned comment added by Mikhaylyuk.1 (talk • contribs) 21:16, 14 October 2014 (UTC)

Co-option and cooptation

Co-option and cooptation are both used in this article, in the section History and definitions, and it is not clear whether they refer to the same or not. Can anyone make clear what they mean and what the differences are, if any? --Alectorolophus (talk) 13:09, 25 October 2020 (UTC)

They mean the same thing. For the sake of uniformity, feel free to change the spelling so that only one form appears. Thanks..--Quisqualis (talk) 03:37, 26 October 2020 (UTC)

Removing a statement

I am going to remove the statement

A behavioural example pertains to subdominant wolves licking the mouths of lead wolves as a sign of submissiveness. (Similarly, dogs, which are wolves who through a long process were domesticated, lick the faces of their human owners.) This trait can be explained as an exaptation of wolf pups licking the faces of adults to encourage them to regurgitate food.

from the Examples section of the article. The reference only mentions muzzle licking in passing and doesn't at all discuss evolutionary exaptation. It's a compelling theory but seems like WP:OR. Noting it here in case someone has some refs or knowledge on the statement. - Procyonidae (talk) 05:41, 4 November 2022 (UTC) Procyonidae (talk) 05:41, 4 November 2022 (UTC)

References

Examples

There's an extreme error in this section: 'This may have occurred with mammalian ancestors when confronted with a large mass extinction about 250 million years ago and substantial increase in the level of oxygen in Earth's atmosphere.' There was a mass extinction 250 million years ago [End Permian] but it was not associated with the Great Oxygenation Event, which was roughly 2.4 billion years ago. I would change the dates but I'm not sure of the relation to the mammalian genome. RobotBoy66 (talk) 22:08, 27 February 2023 (UTC)