richard | 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

Flat | Top-Level Comments Only

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.

New genes usually come in through mutation. It is perfectly logical for many of those old genes to still be there, since they were descended from a common ancestor.

Brilliant, thank you. XD I had to read it a few times before I fully got it, however. >.> The recessive versus dominant genes can linked to the hair and eye color in humans, can't they? Blue eyes and blonde hair being the most recessive?

<3 I love your icon, by the way.

Blonde hair and blue eyes are recessive, yes, although red hair and green eyes are rarer.

Really! That's kind of neat. I have red hair, and sort of green eyes (they're a bit gray, as well).

What's the most common combination, do you know? Brown hair and brown eyes, maybe?

Black hair and brown eyes are the commonest combination. Most of the other variations only appear in European-descended populations.

You are very welcome!

I would think that they were similar, if not the same.

Mendel's peas are related to genetic transmission, but his experiments hadn't anything to do with adaptation, only heredity.

Because, for example, if the predominant predator of, say, gazelle (whatever that would be.. Lions?) became extinct, then gazelle wouldn't need specific adaptions against that predator (running quickly? Longer legs?) so .. I understand it would take significant time for any changes to occur, but do you think speediness would still be a valued trait even if there was nothing to run away from, all other things being equal?

Aha. <3 We're going over genetic engeneering and human cloning in my biology course at the moment, so I did wonder..

This is a highly interesting topic of discussion.. I hope I'm not being tiresome with my questions. I could do with some more research into it, especially since so many people today are inclined to try to debate against and for it.

*Engineering, sorry, don't know how I missed that one. XD

Those traits would slowly diminish based upon the environmental needs.

You aren't being tiresome at all!

Ahh. And that sort of change would take a lot longer than a few human lifespans could quantitatively observe, I imagine.. Hence "macro" evolution versus "micro" evolution of insects, like in your example.

But just because there's not a way to replicate it in a laboratory setting doesn't mean there's not sufficient evidence to accept the theory and teach it in schools, right? I don't see what the big fuss is (Although I admit I'm an explicit atheist to the point where I'd rather see religion become an exclusively private affair between oneself and one's chosen deity, and some people apparently feel threatened by this "evil scientist propaganda" that "people came from monkees"... *eyeroll*).

&Hearts; Well, thank you. I appreciate you taking the time to explain all of this to me.

Evolution.

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