How on earth did *that* evolve?

Great Debates
1

I was taught evolution in High School as fact (like chemistry or magnetism).
I think the “creationist” movement is mostly a bunch of wackos.

However, while watching nature programs on the Discovery channel or Animal Planet, I see things and think “how the hell did that evolve”? I can see why some people might find it difficult to accept that evolution describes how all animals got to be how they are.

So, I would like to know what things make people think: “how the hell did that evolve”, and some answers/guesses from people as to how those things might have evolved.

To start it off, I’ll add something I saw recently. There are some fish who spit water at insects that sit on branches above the water where the fish are. The water makes the insects fall into the water and the fish eat them.

How did such a behavior evolve? The fish has to be able to

  • See outside the water
  • Be able to spit a decent amount of water a decent distance
  • “Know” what to spit at
  • Aim quite well while spitting.

Before any such fish existed, what was the pre-cursor to this fish? What behavior did it develop that lead to the current behavior?

I don’t want answers from creationists who will say “stuff like this proves the existence of an intelligent design”.

I would like answers/guesses from people who take evolution as fact, because I find it interesting how such behaviors might have evolved.

Also, please add your own “how did that evolve?” examples.

2

Ah, the archer fish. Also known as the “Official Proof-Of-God FundieFish™”. (About halfway down the page).

3

I checked it out, but did not see any satisfying answers.
One of the people says

But, the first sentence is a big assumption. In “Start with a fish that for some reason spits at bugs”, what does “for some reason” mean? It’s all very hand-wavy to me.

I don’t like people rejecting questions just because some fundies have brought them up in the past. What is the actual answer to the question?

Anyway, no satisfying answers yet.

4

Quick, someone page Oolon Colluphid!

5

:wink:

6

Can we please stop bringing God into this and address the question?

Also, I would like to hear of other things besides this fish that makes people wonder how that could have evolved.

7

He didn’t bring god into it. Gorsnak made a joking reference to a bit from The Hitchhiker’s Guide to the Galaxy and Desmostylus provided the clip.

8

If you want hard answers, there aren’t any. We weren’t there to see the proto-archerfish spitting at bugs. If you want hypotheses, I can come up with a couple:

  1. It was a random mutation that happened to be a survival edge.
  2. The fish used to jump out of the water to get bugs. One day it just missed a bug and accidentally spat at it, so the bug fell into the water and was consumed. Through positive reinforcement, the fish kept spitting at bugs. This was a survival edge.

The archerfish isn’t even that impressive to me. When I wonder about how things evolved, I think of things like a bird’s wing or a human eye. Those are complex.

9

Well, the wing is pretty easy… sort of. There are other similar things out there… arms and legs, and fins, and such… which, with a little mutation, could easily be converted to wings.

Same thing with eyes. The human eye is pretty complex, true. The dog’s eye is slightly less complex. Other animals have even less complex eyes… down to the barest of light-sensitive spots on something’s skiin. These together provide something of a chain you can follow, and see (pardon the pun) the evolution of the eye.

But what about the fish, man! What the heck?

Well, ok, fish got eyes. They can see. So, seeing a bug isn’t that big a deal.

But the fish has to be out of water. Well, ok, that’s not that big a deal either. Flying fish, lungfish, etc etc. Heck, that’s the cliche’ image of evolution… a fish out of water.

Ok, so what’s next? See the bug, make contact with the bug. Needs a brain that can handle that kind of information. Big deal, animals do that all the time. Next question.

Method of contact: Spitting water.

Are there other fish that spit water? I kinda expect that there are.

So, assuming some sort of proto-fish that has all these abilities, all ya need is ONE that mutates an actual desire to swim up, stick his head out of water, find a bug, and spit it down.

Bingo, the fish lives to reproduce.

“Hey, baby… see that bug over there? I’ll bet you…”

10

One day a fish goes for an insect sitting on the water surface. The insect takes off just as the fish opens its mouth. Some random mutation on this particular fish, plus the fish momentarily breaking the water’s surface, causes the fish to dribble out a little water from its mouth. This is is just enough to catch the insect’s back foot and the fish gets its meal.

Times are hard that summer, there aren’t many insects to be had. This random, fluke behaviour from this particular fish makes all the difference between starvation and survival. Most of this fish’s offspring inherit this little quirk. They equally find it a small advantage in catching insects. Some, however, have inherited it just a little more than others. Their dribble is more of a spit. They do better than the rest.

And so it goes on through generations. The advantage becomes more obvious, it spreads through the entire population, the spit becomes more of a squirt. Somewhere along the line a fish occurs that’s not so good at judging where the water ends and the air starts. But it finds that it’s managing even better by sticking right out of the water. Pretty soon they’re not even bothered about waiting for the insect to land on the water.

And so on…

I’m not saying that’s exactly how it happened, but it’s a plausable explanation in line with evolutionary theory.

The chief problem that people have about accepting this process is because, I believe, they don’t appreciate the unimaginably long time and millions of generations that it takes. The whole thing will have taken a period that is difficult for a person to envisage.

Many critics also can’t grasp the idea of evolution not working towards a “target”. Nothing that happens under evolution is just a progression towards some ideal. Each step only happens because it offers an advantage at that very time. Nothing developed in the archer fish because, somewhere futher down the line, it would allow them to squirt water at insects. At no point was there (or indeed is there) a step of evolution ‘half done’.

11

When you look at complex systems, it is easy to be baffled as to how they could get started, as removing any single component of the system would render the whole system inoperable. This concept is called Ireducible Complexity and is one of creationism’s favourite arguments.

However, the same argument can be applied to non-living, irreducibly complex systems, such as this natural rock arch - no matter how carefully you removed a section of the arch, the whole thing would colllapse because the structure as a whole is dependent on every part being in place - it is irreducibly complex.

But that doesn’t have to mean that:

  • Somebody made it that way
  • It was always that way

At some point in the past, the arch would have been just a solid piece of rock (which would not be irreducibly complex - remove a section and it woould remain standing) - erosion carved away the supporting stone, leaving just the self-supporting arch.
Likewise, with biological systems, it is easy to look at a set of interdependent features and not be able to immediately fathom how they came to exist, because of the level of interdependence (or the severity of removal of one component), but that doesn’t have to mean that:

  • Somebody made it that way

  • It was always that way

  • One thing that can happen is that the irreducibly complex feature sets we now see are the stripped-down remnants of earlier systems with more, or different components, which happened not to be irreducibly complex, either because they contained redundancies, or because they performed a subtly or grossly different overall function.

12

The spitting is the only difficult part.

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.

By disturbing it from a distance rather than close up I think a wider scope of vision is retained as well as distance from such sediments as are disturbed. It’s easy to imagine how spitting started this way. The mouth is a versatile organ.

Once you have that spitting behaviour, it’s small steps to spitting at food, outside of the water.

13

How about this as a first step. Imagine a fish that eats insects on the surface of the water. As it strikes, some insects will dodge out of the way. However, if the fish spurts a tiny bit of water ahead of itself, the insect has slightly less chance of escaping, and the fish has a very slight survival advantage. This doesn’t have to start as a spitting action, in the first instance the fish might just open it’s mouth a bit wider to push more water in front of it. A refincement of this action would be a true spit.

Once the fish can spit, it can attack flying insects a just above the surface of the water. Any fish that can spit more water, spit it further or more accurately has a slight survivial advantage. Give evolution a few million years and I don’t find something as refined as the archer fish remarkable at all.

It might not have happened like this. An alternative scenario is that spitting evolved for a completely seperate reason. However, a fish that spat as it struck for an insect on the surface would gain an advantage.
Evolution works on a timescale which is thousands of times longer than our lifetimes, so it isn’t suprising that we can’t explain everything satisfactorily.

14

To answer the title (and not the specific question about the Archer Fish), read Stephen Jay Gould’s collections of his columns from Natural History. During the decades-long run of that monthky column, the constant theme was Darwin’s Theory of Evolution. Gould always tried to tie into that theme, somehow, and in the process covered masny of the details and pitfalls of interpreting and applying the concepts of Adaptive Radiation, Natural Selection, and Sexual Selection that make up the Theory of Evolution. Well worth the read.

His point is frequently that it’s easy to misinterpret or misapply the ideas, and that there are constant examples to illustrate the rules. Sadly, I don’t think he ever covered the case of the Archer Fish, but I can see how it could evolve.

One of the points Gould raises is that Evolution relies upon changes in the existing structure, so that radical departures from what’s already there simnply don’t happen. The Panda has a ersatz “thumb” because an existing bone could easily develop into it.

Archer fish use an unusual combination of skills and abilities, but it’s not an impossible or even an improbable set. If there was a fish that use laser beams to shoot down insects, or a fish with arms that snatched insects down from plants, that would be a radical departure from the probable and possible. Evidence for the existence of God (or of practical jokes-playing space aliens, maybe). That such radical departures do not occur is, Gould argues (in essence) one of the factors arguing for the theory of evolution.
An even better argument for Intelligent design (and one used a lot by creationists) is the evolution of wings for flight. After all, half a wing apparently isn’t good for anything, so how can as complex a structure as a wing have evolved in the first place? (Tom Weller, in his wionderful parody Science Made Stupid, argues for the existence of an intermediate form, Monopterosaurus, that possesed one functional wing. It chased its prey in small circles around trees.) Where Creationists see an impasse that requires belief in God to explain, Evolutionists see simply inadequare knowledge and unresolved questions – exactly the kind of thing scientists lust after, since that’s where creative and productive work can be done. There has been a lot of exciting speculation in this area of the evolution of wings in recent years.

So, you see, it’s a cultural divide. “Never the twain shall meet.” What Creationists see as a trump card proving their case (unanswered and seemingly unanswerable questions about how something could have evolved), Evolutionists see as an opportunity and their natural domain.

15

Other examples of creatures that you wonder ‘how did that evolve’ are Bombadier beetles and flagella.

Both of these have been discussed on TalkOrigins and other sites.

16

Another classic example of the (creationist) argument is the vertebrate eye, often combined in a double-whammy with a classic (dishonest) quote-mine; something like this:

The eye cannot possibly have evolved because the lens is useless without the retina, the retina is useless without the optic nerve (and vice versa) and the whole lot is useless without the visual cortex (and vice versa)… Even Darwin himself addmitted this when he wrote “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…”

Always look for the ‘…’ when creationists quote non-creationists because it most often represents something they have deliberately (and dishonestly) omitted because it harms their argument; in this particular case, Darwin is presenting a rhetorical objection, which he goes on to answer in the sentences immediately following the snipped quote.

17

One thing that is often missed in references to archer fish (Toxotes jaculatrix) is the fact that shooting bugs off of leaves is not the only means they have of acquiring food. They also hunt assorted water bugs and even small fish. Further, they have a couple “out of water” hunting techniques - the most obvious being the water-shooting which gives them their common name, but they are also quite capable of simply leaping out of the water (sometimes as much a 6 feet) to just grab or knock their prey from a leaf or branch.

As such, it is likely they evolved from more mundane ancestors, which may have had within their bag of tricks the ability to leap out of the water to catch choice insects. It may be possible that in preperation for this leap, a voluntary (or involuntary) spasm caused a jet (or a dribble) of water to shoot out of its mouth, which may have, in some early cases, done the job without having to leave the water after all. From there, it’s relatively easy to refine that trait, so long as it proved advantageous.

The biggest problem with many of these “how did that evolve” questions, though, is that we simply do not know enough at this time to be able to explain each and every trait out there. We must infer a great deal, but those inferences provide starting points from which we can set up hypotheses for testing. In some cases, though, we may simply not have enough data to provide an adequate explanation. Unfortunately, creationists and IDers delight in using these areas of inadequate knowledge as “proof” that evolution just couldn’t happen. Never mind, of course, the numerous traits and phylogenies which we do have suffficient data for to put forth a reasonable epxlanation…

18

Also, you don’t have to explain every organ’s evolution to convince me of natural selection. At one point “Fish could never develop lungs” or “what good is half an eye” would have been a cogent objection. Then someone found a lungfish or invented a potential path from light-sensitive skin to an eye.

If each objection keeps being demolished, new objections start being met with “Sure, we’ll figure out how archer fish evolved. Here’s a few ideas to start with.” rather than “Damn! It seemed so promising.”

Analogy: You see a ball floating in the air. Is it more likely that there’s a fan under it, or some other suspension you didn’t notice, or that gravity doesn’t exist and God for his own reasons wanted to trick you into thinking it does in all cases but this one?

19

One thing that has not been addressed here is the whole gimmick of pre-selected adaptations and behavior.

Consider, if you will, the numbers of quadrupeds prevalent in the wilds of, say, northern Ontario. Presumably there are a few frogs, salamanders, snakes and turtles which estivate. But the overwhelming majority of smaller-than-a-sheep chordates are mammals and birds – because they have the capacity to generate a stable body heat and the insulation to retain it.

Contemplate a small running dinosaur, varmint-carnivore like a fox or skunk would later be, bipedal as most such dinosaurs were, dealing with the cold season in a temperate climate. It’s advantageous to have insulation, so selection for scales that fray to become down is beneficial – and scales that become proper feathers, even more so. But feathered forelimbs are approaching winghood – and arboreal predators who used their feathered forelimbs to help break their falls tended to survive better than those which fell out of trees and did not so use them.

Likewise, lungs appear to have evolved very early in the fish lineage, although only a few of the lungbearing lines retained them. Other lineages adapted them as swim bladders and oil reservoirs. And the purpose was not life on land, but survival in stagnant waters – though there might be very little oxygen dissolved in the water and available to one’s gills, one need only stick one’s head above water to find oxygen in the air above, provided one had lungs to breathe it with. Present-day lungfish use their lungs for precisely this purpose. But if one has lobe fins capable of supporting one’s weight and lungs capable of breathing air, one can make some use of the land surrounding one’s pond, whether to escape one’s predators or to feed on the insects already present on land, or merely to get from a drying and useless puddle to a larger pond that has more chance of lasting through the droubt.

20

In my youth I was an avid freshwater fisherman. In pursuing this hobby I made many empirical observations of bass and sunfish behavior, and viewed many films of underwater bass and sunfish hunting and nest defense methods.

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.

2: Fish eyesight is not that bad at or near the surface as many a frustrated fisherman can attest.

3: Insects on rocks and branches are low hanging fruit, and many fish will readily leap out of the water to snatch them off a rock or twig above water.

In this context it is hardly baffling that some fish would employ the underwater water jetting method of routing prey to go after insects just above the surface, and (if successful) this ability would develop itself across milion of years into an ability to shoot water aross several feet.

Why is this such a huge evolutionary brain teaser? The fish is simply employing a skill above water, that it already well developed and sucessfully used below water.