So we have some animals, one of them mutates, and if the mutation makes any significant difference in the animal’s ability to reproduce, it gets naturally selected. When do the mutations add up to a new animal?
I probably have other questions, but I don’t know what they are until I hear some discussion
Ooh! If “survival of the fittest” really happens, have there been species that didn’t make the cut?
Also, I just remembered learning that what makes a different species is an inability to reproduce with other specieses. So when and why does an animal develop that inability?
Is the mule a sin against nature?
There is no “eureka!” instant where one species is transformed into another. (Although occasionally the process happens quickly enough that humans can observe it happening on a human, or at least human historical, scale—see Observed Instances of Speciation at Talk.Origins, which by the way is a very good site for learning more about evolution). Say you had a brick wall, and you replaced the bricks with stones, one stone for one brick at a time. At the end of the process, you’d have a stone wall. If you could put them side by side, you’d say they were two quite different walls. When did the old brick wall become the new stone wall?
At least 95% of all species that have ever lived are extinct.
If two populations within a species diverge, eventually enough differences will accumulate that those populations will no longer be able to interbreed. These differences can be behavioral–group A is noctural; group B only comes out during the day–or more profound–one developing species may wind up with a different number of chromosomes from its sister species, meaning offspring will be impossible or will be sterile if born. Reproductive isolation is often, though not always, accompanied by geographical isolation–the group on the other side of the sea or the mountains or the desert diverges and eventually can no longer interbreed with the group on this side, even if the sea later dries up or the mountains are worn down, and the two daughter species once again share a geographic range. As would be expected if species are formed by branching off from each other, the line between species can be fuzzy. The existence of mules and other hybrids between closely related species is actually pretty common. With artifical insemination, people have been able to cross-breed animals like lions and tigers, which would never occur naturally.
There is no such thing as a “sin against nature”. Evolution is not a person, and evolutionary processes make no value judgements. Mules are no more sins against evolution than airplanes are sins against gravity.
Exactly right. It is interesting to see the word “sin” used at all on this subject. It seems to me that anything that happens in nature is natural, even if brought about by humans or other animals. After all, we are a part of nature.
I think the concept of “sin” depends entirely upon a local, cultural determination of what is “right” and “wrong.”
Ditto to the endorsement of the talk origins website. Also, you might consider the following links for some discussions on species concepts. Thanks goes to Tamerlane for directing me to these links a few months back in another thread.
http://www.tulane.edu/~eeob/Courses/Heins/Evolution/lecture6.html
http://www.ebi.calpoly.edu/BioSci/Courses/BIO/BIO414/MacroEvol/Mac03.html
You did pretty well in the first round.
I know there’s lots of extinction, I was wondering more if there have been observations that explain how something became unfit for its environment. I bet there were all kinds of interesting monsters that killed themselves off before people started killing off the otherwise healthy animals.
How do large mutations happen? I’m thinking legs instead of fins, something like that. What could happen to a developing animal that would turn it into such a freak?
How do these freakish changes catch on? Wouldn’t the little fishy who had legs have too many problems swimming to worry about mating? If the fin to leg thing never happened, there must have been something equally grand that someone who knows more on the subject can suggest. How about a change in the number of chromosomes? How would the first animal who had this mate with anyone with the original number?
What have been some helpful human mutations? I’m thinking sickle cell blood, what are some others?
How does it work out that one combination of bases in DNA gives you round blood cells and another gives you sickle cells? Why not some other shape? Is no one else freaked out that traits come out of a range or choice of possible traits? Where does this range come from?
Do humans have a known evolutionary predecessor? What seperates us from them?
I’m not buying your brick to stone wall analogy. When you add the first stone, it’s not a brick wall anymore, nor is it a stone wall.
Thank you, everyone, for participating in this. I knew if anyone could educate me, it’d be the TM.
Now that that’s taken care of, “sin against nature” is a joke I hear a lot. Maybe it’s a local thing.
Based on your questions, it’d probably be easier if you read the FAQs on talkorigins.org first. There are a number of misconceptions in your post that could be cleared up there, then you can ask more detailed questions here as follow up.
I agree with Telemark; many of your questions reflect a misunderstanding of the basic concepts of evolutionary theory. (I’d say that some of the things you’ve said indicate that you may have gotten your ideas about evolution from the caricature of evolution that Creationists present in their literature.)
According to one of the most popular theories regarding evolution’s mechanism, adaptation happens very slowly on a human time scale, but very rapidaly on a geological time scale. In other words, if you look at fossils there seem to be larger jumps in differences between forms than there may actually have been. Lobe-finned fishes, for example, likely did not just give birth to a salamander one day; that is the relevance of the brick/stone wall analogy. You start off with a brick wall, you end up with a stone wall; between the two are differing percentages of stone and brick that occur leading up to the wall being completely stone. The intermediate forms are in sort of a “grey area” of classification.
A Creationist will read that and say “A HA! So you’re saying there should be “missing links!” Well, where are these “missing links”??” To answer, first I’d direct them to the talkorigins web site again to the transitional fossils FAQ. Then I’d beat them over the head with a Nerf bat.
First round?! Don’t flatter yourself. Trust me you’re still doing bag work and shadowboxing with a clumsy notion of what of current science says about evolution. Read the faq.
For that you need to study molecular genetics. Fascinating subject, and one that an intelligent and motivated layman (non scientist) can come to understand, if they wish.
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I, for one, am not freaked out. Would you prefer no range at all? Then everyone would be exactly the same.
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Why, it evolved, of course.
How about the Dodo? - it became unsuitable for it’s environment (or at least it did once that environment started to include humans).
Interesting that this thread should appear now; just the other day my boss was saying to me that he finds the theory of evolution the most implausible thing ever.
The odd thing is that he doesn’t have any better explanations, he’s certainly not a creationist or anything. The conversation included such gems as “If humans evolved from apes, how come there are still apes?” and “If it’s advantageous for giraffes to have long necks, why isn’t is advantageous for all animals to have long necks?”.
evilyam, may I ask what explanation or theory you would like to offer in place of evolution?
It’s only an analogy (and analogies are dangerous because we push them for more detail and they break down, but that doesn’t make the concept they were illustating false).
What MEBuckner said still stands even without the brick wall analogy; when the process of change is gradual, there is no ‘moment’ when it ceases to be A and becomes B.
In fact, all of the species that exist around us today are in fact subject to gradual changes, the classifications we have given them reflect a ‘snapshot’ at the current time; come back in a few hundred thousand years and you can expect a little trouble in identifying many organisms against today’s textbooks, but the point is that things will have changed by all kinds of varying amounts depending on the varying conditions that selected them.
I’m too tired to really get into this whole thread, but this one popped out at me, so for what it’s worth, I figured I’d answer it.
Sickle cells are due to a mutation in the gene that codes for hemoglobin. Where a normal hemoglobin molecule has an uncharged amino acid, the mutated gene places a charged amino acid. This charged amino acid is attracted to a certain oppositely charged amino acid on other hemoglobin molecules. Because of this attraction, mutated molecules link up into long chains, which normal molecules cannot do. It’s these chains that give the cell its sickle shape.
Actually, the mutation creates a greasy spot which is attracted to other greasy spots on other hemoglobin molecules via the oil-and-water effect. Otherwise, your description is more or less correct.
I should add that sickle-cell anemia is a classic case of segregational load. If you have one gene for malaria-resistant hemoglobin and one for non-malaria resistant hemoglobin, you end up better off than if all your hemoglobin were resistant (causing sickle-cell disease) or non-resistant (leaving you vulnerable to malaria.) The problem is that the two genes share the same locus, so if you have both genes in a population, a lot of the time descendants will get shafted by inheriting two copies of the same type of hemoglobin, one copy from each parent.
In such cases, there’s a lot of evolutionary pressure to duplicate the locus, so that everyone can have two copies of both genes- for example, people could end up inheriting a resistant and non-resistant hemoglobin from their mother, and a second copy of both genes from their father.
If you want to learn more about molecular genetics and evolution, here’s the link to my FAQ:
Please keep in mind, in addition to what others have said here, that evolution is not restricted to animals. All living organisms, be they plants, animals, fungi, protists, bacteria, archaeans, and even virii, are subject to mutation and natural selection.
Even a penicillin-resistant bacterium can be “new” in an evolutionary sense.
evilyam, go to a textbook on paleotonology and look up Diplocaulus, an early amphibian that many scientists believe died out precisely because it was not well-suited to its environment.
Ehhh…I’m not quite sure what you mean by this. Why do many scientists believe this?
Cruickshank and Skews[sup]1[/sup] did a biomechanical analysis of Diplocaulus and found that the odd skull shape worked quite well as a hydrofoil when held horizontally or tipped up slightly, allowing it to lie in wait at the bottom of a pond, and quickly grab fish swimming above with a sharp flick of its tail. Based on the paleontology texts I’ve read, it doesn’t appear to have been at any particular disadvantage because of its odd appearance.
Of course, this doesn’t change the fact that it did, like so many others before and after, go extinct eventually.
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[sup]1[/sup]Cruickshank, A. R. I. & B. W. Skews 1980. The functional significance of nectridean tabular horns (Amphibia: Lepospondyli). *Proc. R. Soc. Lond. B *290, 513-37.