richard | Evolution.

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Evolution.

I'm afraid that I'm about to go on a bit of a pedantic tear, but a rather interesting post by naamaire inspired me to do it. It has come to my attention that many people, particularly those who subscribe to Creationist models, seem to misunderstand completely how the theory of evolution works. Those more knowledgeable than I about evolutionary biology may add information in the comments if they wish; I think that such a thing would be most useful.

I apologize for any incoherency, as well as typographical, orthographical and grammatical errors. It is late, and I am tired.

Many people misinterpret the theory of evolution; they seem to think that it has something vaguely to do with monkeys, or that it involves elephants' giving birth to hippopotami (or any other combination of a species giving birth to another). Those are gross oversimplifications; that is not the way in which evolution works at all. The theory of evolution describes gradual changes (and when I speak of gradual changes, I am speaking of changes that very well may take millions of years) in organisms that allow them to adapt to their environment. A dramatic change, like the elephants' giving birth to hippopotami that I gave in my example, would actually be antithetical to what evolution posits.

Organisms evolve through mutation and natural selection. Genes do not always copy themselves perfectly from parent to child; sometimes they mutate for no apparent reason. If the mutation happens to be adaptive, then the organism that harbours the gene will pass it on to its children, and if it is maladaptive, then the mutation will generally make sure that the organism does not live long enough to reproduce; therefore, such genes would not be passed on to the children. This would go on for quite a long time, making it very possible for new species to come about.

I should give an illustration so that my readers can understand better what I am talking about. I am sure that most of my readers are well aware of insects that evolve to be resistant to insecticides. When farmers apply such insecticides to their plants, those insects who happen to have (for whatever reason) a greater resistance to the pesticides will be more likely to survive and reproduce with each other, giving rise to more insecticide-resistant insects. Those who are not resistant will die. I know that many creationists will stop me there, and will try to call such evolution 'micro-evolution', which they admit exists, but will call larger-scale evolution (which is simply more 'micro-evolution' over a longer period of time) 'macro-evolution', which they dismiss. This is a fallacy; species tend not to come about during the course of human lifetimes. In fact, humans have been on Earth for rather a short time and have not had enough time to observe evolution directly, especially for large and complicated organisms like ourselves. Large-scale evolution does not happen in an instant. That we can see the sort of evolution observed in these insects is remarkable as it is.

The idea of organisms' suddenly giving rise to a newly evolved form and the argument about transitional forms' not being found are both utterly preposterous. Scientists do not believe this, and I am sure that they do not expect laymen to believe this, either. Of course a species only gives birth to its kind! It would be foolhardy to assume otherwise. Evolution's gradual nature, discussed earlier, makes that extremely improbable. Regarding the question of extant transitional forms, Richard Dawkins discusses transitional forms in an essay entitled 'Gaps in the Mind' in his book A Devil's Chaplain. He gives an example of transitional species in the form of the Herring Gull and Lesser Black-backed Gull ring.

The best-known case is the Herring Gull/Lesser Black-backed Gull ring. In Britain, these are clearly distinct species, quite different in colour. But if you follow the population of Herring Gulls westward round the North Pole to North America, then via Alaska across Siberia and back to Europe again, you notice a curious fact. The 'Herring Gulls' gradually become less and less like Herring Gulls and more and more like Lesser Black-backed Gulls until it turns out that our European Lesser Black-backed Gulls are actually the other end of a ring that started out as Herring Gulls. At every stage around the ring, the birds are sufficiently similar to their neighbours to interbreed with them. Until, that is, the ends of the continuum are reached, in Europe. At this point, the Herring Gull and the Lesser Black-backed Gull never interbreed, although they are linked by a continuous series of interbreeding colleagues all the way round the world. The only thing that is special about ring species like these gulls is that the intermediates are still alive. All (Dawkins' emphasis) pairs of related species are potentially ring species. The intermediates must have lived once. It is just that in most cases, they are now dead.
Richard Dawkins, 'Gaps in the Mind' from A Devil's Chaplain, p 22

Dawkins' example says it rather clearly. Transitional forms do exist.

I hope that this little write-up serves well in explaining how evolution works. If anyone has questions, do ask, and I shall either answer them myself, or point you to something that would answer the question for you.

Further reading
Richard Dawkins' The Ancestor's Tale
Richard Dawkins' The Blind Watchmaker
Daniel Dennett's Darwin's Dangerous Idea
TalkOrigins.org

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Thanks Richard I just never understod Eveloution or I thought it might be "part" of the puzzle but nevr a absolue in my mind I think when your in a group you have to enbrace many theroies as plausable to explain how some are here and all. But I relly do enjot Intillectual Desighn stuff too cause well even SCientists are saying theres something Higher and a missing link so I try to blend them both Cause I think all cretures are always EVOLVING and that can be seen not just by cross breds in annimals but if you look at horses the dogs or Lions then kitty cats or Beavers then squrrels ya know and we are always developing in humaness but I just know for me a Higher power had something to do with creating from the beginning I enjoyed your post and it wil make me read more about ideas and schools of thought
*hugs* Astrid with soe bratz

By friendslocking the post, you seem to be preaching to the chior. Just saying. ;)

I've changed the security so that those not on the Friends List may see it as well. It was written for the benefit of someone who is on the list, and I was planning on making it public, but I locked it out of habit.

You're very welcome, all of you. I hope that it helped. *Smiles.*

If no species ever gives birth to another species then all life on Earth must be the same species. Saying that it happens very slowly doesn't change the fact that speciation has occurred. You describe changes within members of species and say that explains speciation. It doesn't. Human beings have been breeding dogs for thousands of years and introduced great variation in the species, yet they are all dogs. All of Darwin's famous finches are the same species of finch. The gulls in your excerpt from Dawkins are all gulls-- the reason that the ones on the far ends don't breed is that they live too far apart.

Following Dawkins' logic, all creatures on Earth can interbreed, since they are all related. Such turns out not to be the case.

To give one example, let us consider the bat. Evolution would say that the dactyls gradually grew longer until they became wings. So for millions of generations some species of mammal must have existed that had limbs that were too elongated for walking and too short for flight. How, precisely, did this long vanished creature survive?

I'm not familiar with the evolutionary history of bats, but I wouldn't be surprised if the intermediate form was something like the flying squirrel or sugar glider. No need to travel by ground, when you can climb and glide.

Some species can interbreed, but the resulting offspring isn't capable of reproducing on its own. (See mules, and tiglons/ligers.) Rather circularly, that's how we define 'species' in the first place. At some point along the line, one subgroup or another becomes genetically incompatible with the rest.

Actually, the flight mechanism of flying squirrels is completely different than that of bats-- bats wings are long fingers, essentially, while flying squirrels and sugar gliders use loose underarm skin. Morphologically, they structures are as different as a squid's tentacles and an elephant's trunk, despite similar uses.

And you bring up my original objection: "At some point along the line, one subgroup or another becomes genetically incompatible with the rest." If evolution occurs due to mutation, and mutation occurs to single individuals, with whom do these mutated individuals breed? Whether it happens fast or slow, somewhere along the line there must be one individual that is incapable of reproducing with its breeding group, so how are those genes transmitted? A random mutation cannot happen to a large group of individuals at once.

Evolution is a tree of life. New species that branch off older species are part of those very branches. Of course they are still gulls; no evolutionist worth his salt would say that gulls did not descend from other gulls. The great apes who descended from a common ancestor may very well be separate species that cannot interbreed, but they are all still great apes.

Speciation is, as I said earlier, based upon adaptations to environmental conditions, as well as other conditions. The first organisms had to have travelled and found themselves and their descendants in different areas, which clearly gave rise to new species.

Such a creature would not be able to survive. As I said before, evolution is about adaptation to an organism's surroundings. It simply would not happen because it is maladaptive. Such a creature would actually run counter to the idea of natural selection.

Here is an article that elaborates this further: http://talkorigins.org/indexcc/CB/CB925.html, and this page is rather good, too. http://talkorigins.org/indexcc/CB/CB921_2.html

None of these mutations are terribly large on their own, so they would certainly be able to transmit the more adaptive genes amongst each other.

That is to say, populations evolve, rather than individuals. As I said, none of the mutations would be terribly large on their own, so the new genetic information would be able to be transferred. Speciation is generally not sudden.

I said "something like" not "identical to". A critter with elongated webbed fingerbones that could both glide and cling to trees. You'll note that modern bats retain a grasping finger or two, for similar purposes.

Mutations occour to individuals, evolution happens when mutations spread across a subset of a species. You're correct to observe that no single gene is completely responsible for differentiation of species, but sooner or later there's a 'last straw' that prevents subgroup A from interbreeding with subgroup B. Often, it doesn't matter at all to groups A or B, because nonbiological factors (such as geography, etc.) had prevented them from exchanging genes for a good long time to begin with.

I'm sorry, I seem to expressing myself poorly. I do not deny that there are wide variations within a species, nor do I deny that different species use diverse means to achieve the same ends.

My objection to evolution, such as you define it above, is that I don't believe that transitional forms, such as hypothetical "half-bat" with wings too short for flight and too long for running, can survive, much less compete with their non-evolved kin. To give another example, which evolved first, fibrogen (the substance in mammal blood which causes clots) or the fibrogen antagonist, which prevents blood from clotting prematurely? Did the muscles which control the flexing of the lens of animal's evolve before or after the evolution of the flexible lens? Were there fish with rigid skeletons before their were fish with lubricated socket joints allowing for the articulation of those skeletons? Or did the socket joints evolve in cartilaginous fish who had no use for them?

I don't insist on answers to all of these questions, but before I accept evolution as a viable theory I would like to see some theoretical mechanism for explaining them. Pointing out that some reptiles have skin that can sense heat variations does not explain how the humor inside eyeballs just happens to have to proper reflective index to allow for clear imaging.

You seem to be expressing yourself rather well.

I do not think that such forms can survive either. That is actually the point - if such creatures were born, they would not survive and pass their genes on to other individuals. Such creatures' survival would be a good disproof of evolution, not a confirmation of it. I think that we can agree here.

These things would have probably come about gradually, and through simpler forms. There wouldn't be any way for them to exist separately - evolution has never claimed that. That isn't an argument for any form of intelligent design, either; rather, it is an argument for the sort of slow, adaptive change that would allow such a thing. I'll link you to a few examples that illustrate my point well. The examples include that of the bombardier beetle, which already had a chemical mechanism in place that evolved further in order to protect themselves, and a means by which to do it. All those changes were gradual and were not as impossible as they seemed. Here is a more detailed discussion of the bombardier beetle: http://talkorigins.org/indexcc/CB/CB310.html

The eye's humour does not 'just happen' to have a proper reflective index. It just appears that way because we have not seen it evolve in ourselves. It is the result of millions of years' worth of natural selection that caused its mechanism to become more refined.

No, actually, a critter with elongated fingerbones could not glide. The mechanisms for gliding and winged flight are very different, that is my whole point. Gliding is not primitive flight, it is a separate means of locomotion. Heat sensitive "eye-spots" are not primitive eyes, they are a different mode of perception. Reptilian hearts are not primitive mammalian hearts, they are different form of circulatory pump. The snout of a tapir is not a primitive form of an elephant's trunk, different muscle groups and bone attachments are used. The evolutionary chain simply isn't there, and grouping animals that look somewhat alike doesn't qualify.

Ahhh, and this explains why trees developed bark, as a defense against millions of years of animals with partially developed eyes bumping into them.

Seriously, though, I am simply trying to point out that evolutionary theory shouldn't be accepted as fact when it leaves so much unexplained. I remember when it was a proven fact that dinosaurs were cold-blooded, and then it was a proven fact that they were primitive mammals and the latest proven fact seems to be that they were primitive birds (or has that changed?)

If the theory of gravity could explain how some objects fall, but couldn't explain how others do, I wouldn't accept it either.

I like TalkOrigins, except that they don't recognise the Flat Earth Society as a joke. That makes them look quite bad xD

I'm sure people have pointed out that the FLS is a satire...

Any scientist worth their salt would never claim 'proof'. That's very much the domain of the media who takes this stuff and reports it to the public. Evolution is a theory, and that shouldn't devalue it. 'Religion as fact' is objectively far more tenuous as a theory than evolution is. They are both theories, of a sort. I'm inclined to go for the hundreds of years of study and accompanying mistakes and re-adjustments than the assurance of a book or three written before they understood the earth was round.

The theory of gravity isn't exactly linear as well, when you start getting into the nature of space-time xD

I guess the thing with that first comment (which made me snerk water on my desk) is that these animals wouldn't have bumped into trees: they would be living in habitats that suited their limited visual ability. If you're asking 'where do these species originally come from, to start evolving?', there's no simple answer. Basic lifeforms adjust and adapt to increase in complexity, and adapt specific traits to deal with their environment. A grex, for example, is an interesting look at what algae can evolve into when the need arises.

As to the dinosaur question, the current theory holds that dinosaurs, in their many species, were the berach between birds and reptiles. The older ones were more reptile-like, the later ones more bird-like. Vestigal feathers, complete feathers and extensive bird-like traits are found in late-Cretaceous period dinosaurs.

Complicated stuff, and I'm still really foggy-headed. Hopefully it makes some kind of sense xD

Not sure if you've ever come across the notion of punctuated equilibrium (http://en.wikipedia.org/wiki/Punctuated_equilibrium) -- basically, it's a theory that attempts to account for the apparent "bursts" of biological diversification interspersed between long periods of population stasis. Stephen Jay Gould (http://en.wikipedia.org/wiki/Stephen_Jay_Gould) was the primary proponent of this theory.

Evolutionary theory in any incarnation, however, does not make any claims about being perfect or capable of explaining everything about life on earth -- it's just the best fit to the data we have so far. That's the thing that separates science from dogma -- science admits its imperfections and remains open to new data all the time. At least ideally. Sometimes I do think some scientists end up becoming dogmatic -- particularly in areas like neuroscience -- but once they do that, they aren't practicing the scientific method anymore.

It is?! I didn't know that, actually...

With all the crazy people on the Internet, it is sometimes very difficult to figure out what is satire and what is not. Case in point: these tinfoil hat folks (http://aliensandchildren.org/ThoughtScreenHats.htm) seem to be serious!

Is evolutionary theory even being taught in schools these days? I don't remember how I learned about it; there was perhaps a brief lesson about Darwin and the Galapagos, the rest I would have gleaned from private readings.

Great post. I'm bookmarking this for sure.

Two things, though. One, I second azalynn about punctuated equilibrium-- evolution probably occurs in fits and starts, and isn't always a slow, steady march toward advancement.

Also, a lot of people seem to get evolution mixed up with Lamarck's theory. If a giraffe reaches for high food and stretches its neck, its offspring don't inherit a longer neck. Just like a person who had their leg removed doesn't have legless children. Once you make it clear to them that this isn't what evolutionary theory is suggesting, people usually get a bit less hostile toward it. Not a criticism of your article, just an added thought. :)

Actually, the idea that the bible was written by people who thought that the Earth was flat isn't true either. The Babylonian Talmud makes it clear that the Earth was known to be spherical, to hang unsupported in space, to orbit the sun, and to have seasons based on axial tilt for some thousands of years. In fact, I know of no time period in which it was widely believed that the Earth was flat. Columbus was not expected to sail off the edge of the world, he was expected to die of hunger before he reached India (which he would have had not the Americas gotten in his way. The fact is that he was wrong and those who spoke out against him were right, regarding the size of the Earth. It just so happened that there were a few more continents than were known of in Europe.)

Evolution isn't "fact," it just happens to be our current best explanation. Of course evolutionary theory will be reworked extensively, or perhaps even replaced, as we get more information. Just because it isn't perfect at this exact moment doesn't mean you shouldn't place *any* stock into it. I'm not trying to say dissent is bad (hell, it's what makes science science). But by that same token, if we didn't make some educated guesses and assumptions in science, we wouldn't get anywhere.

Oho. I like this post a great deal, it's a very simple and to-the-point explanation of things that usually lose me in biology class. (Ever get the sense you almost grasp something but you're missing it by just a little bit? I hate that.)

Since you said questions are okay, and even though this might be a stupid one, I thought I'd run it by you. Is the evolution of animals (or plants, or fungi, or whatnot) more dependent on environmental conditions or predatory conditions, or are they both considered the same thing? I recall being told about moths near a factory where the trees were black from pollution, and the darker moths survived while the lighter ones were preyed upon because they stood out in relation to where they lived.

Oh! And do Mendel's peas have anything to do with this? Or is that a horse of an entirely different colour?

Thank you. ♥

~Theo

What is significant in natural selection is that an individual is more likely to reach breeding age, and not why. If the climate changes to a longer winter the local herbivores with thick white coats will do better than those with thin brown ones and if an animal with a thick white coat is better adapted to survive it doesn't really make any difference if the coat keeps the organism warmer in winter or is less visible to predators. So the existence of predators can be considered part of the environment-- as can the existence of prey. In the above example the environmental factor of herbivores with white coats would favor predators with a more acute sense of smell, who were less dependent on seeing their prey.

What Gregor Mendel demonstrated with his selective breeding of pea plants is that organisms pass characteristics along to their offspring by some method other than gross morphology-- that is, two adults who do not possesses a particular trait could have a child that does. From this he posited the existence of genes and the theory that some genes are recessive and some dominant. The existence of recessive genes allows organisms to carry within them blueprints for traits that do not suit the present conditions.

To go back to the example of the lengthening winter, if the thick white coat were a recessive trait, very few individuals would exhibit it, although most could carry it. As the snow stays longer each year, however, those few individuals who do exhibit the "white coat" gene live longer and have more children, until virtually the entire population has white coats.

The species doesn't grow any new genes in response to the climate change, rather genes already present in the species become more useful and hence more prevalent.

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