Is the theory of evolution taught as fact or as a theory in schools? And for that matter is it actually a theory or is a fact?
This is an unfortunate case of scientific terminology not jibing with mainstream terminology. “Theory” means something completely different in scientific parlance. Roughly speaking, a theory is a set of mechanisms explaining how something happens that has survived repeated tests.
FWIW, the fact that all organisms desecended from a common ancestor is about as established a fact as any. The theory of evolution is a set of hypotheses as to how this occurred.
The situation with the schools is complicated to say the least. I’m not going to comment.
Someone will be along shortly who has a better explanation. In the meantime, you should check out talkorigins.org, a great site for learning about evolution.
That’s quite a name you’ve got there.
Evolution is both fact and theory, and, when properly presented, is taught as such (in large part, how it is actually taught will depend on who is doing the teaching and how firm a grasp they have on the subject).
As FACT: Organisms change. This is the essence of evolution. The only viable alternative explanation for this observable phenomenon is that of Special Creation – the idea that ALL organisms are INDIVIDUALLY created by God on an ongoing basis. Deifnitely not testable, and therefore not helpful in the least in terms of udnerstanding.
As THEORY: The mechanisms for how organisms change are still debated. Darwin, of course, suggested two primary mechanisms: natural and sexual selection (both analogous to the well-known processes of artificial selection in agriculture and animal husbandry). Natural selection he ascribed the most importance to, stating that this is the process most responsible for speciation. With the advent of genetics, other mechanisms have been proposed, as well as introducing debate as to where, exactly, natural or sexual selection act (e.g., at the organism or genetic level?).
How was the fact that all organisms descended from a mutual one established? Ultrafilter, you say that a theory is a set of mechanisms explaining how something happens that has survived repeated tests. So how can you say that the Theory of evolution is a set of hypotheses if a hypothesis is an untested theory? Care to clerify?
This thread is surely destined for Great Debates. It may even be the classic example of same. But before then, a relevant comment about the word “fact.”
As I understand it–and I would say I have a fairly good layperson’s acquaintanceship with science–a “scientific fact” is a description of some situation of interest to a branch of science (biology, physics, etc.) that is regarded as noncontroversial among those actually practicing within that field. Imagine various proposed descriptions (proposed formulae, mechanisms) listed across a page at the bottom of a bar graph, with each bar indicating the degree of confidence that the relevant practitioners (as a consensus) have in the truth of that proposal. Some of the bars will be very high, showing a robust commitment to that proposal as a “fact”; others may be very low–these remain conjectures or hypotheses. The point is that there are many possible degrees of confidence; it follows that whether a proposal is regarded as a “fact” depends upon just where that particular branch of science chooses to draw the line.
You are raising (or implying) a sort of world-question; that is, you are asking, not whether biologists think of some sets of proposals as facts, but whether they “really are” facts from a general point of view, outside the particular disciplines and perhaps outside science as a whole. But there just isn’t any universal rule for proper line-drawing, and thus no way to assess the facthood of a belief “from the outside.” (More precisely, no criterion for assessment that is particularly indisputable.) At least part of the argument to which you allude is a dispute between two genera of inquiry–science and religion–over who has the right of ownership over the word “fact.”
This is another instance of scientific parlance differing from the everyday. A hypothesis is not untested. In fact, the first thing you do with a hypothesis is test it. There’s a good explanation here.
There’s a great write-up as to how common descent is established here. In short, the main evidence comes from DNA sequencing.
btw, if you want to reply to a specific post, hit the “quote” button underneath their post. This sometimes aids in clarity.
Memnojokasel Durinjio:
In fact, this “fact” has not been established. As has been said, it is a fact that there are huge commonalities in the structure of DNA of all living things. The most probably explanation is that all living things inherited this structure from a common ancestor. It is not the only explanation and it is certainly not a tested explanation, so to call it a fact is scientifically reckless.
Also, to the point of the initial question; there really is no ONE theory of evolution. There are lots of little sub theories, some of them are more substantiated by fact than others. Having two kids in high school I can say that it seems to be taught much more emphatically than I feel comfortable with. The textbooks (and one assumes instructors) still cite bad examples, for instance Industrial Melanism as evidence of Natural Selection. Bad supporting evidence can often do more damage to a good theory than any counter theory.
Off to Great Debates.
bibliophage
moderator GQ
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No? If a mountain of fossil evidence points to common descent as a hypothesis, and that hypothesis is massively vindicated by a mountain of DNA evidence, that doesn’t count as “established”?
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Actually, that’s a gross oversimplification of how the DNA evidence really works. See section 3 of my FAQ:
http://psyche11.home.mindspring.com/molevol2.html
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On the contrary, it’s been tested over and over again, and has been massively vindicated. Arguably every gene that is sequenced counts as a test. Moreover, the recent discovery of whale fossils which were predicted on the basis of DNA evidence also constitutes a test, and a particularly impressive one.
Why isn’t Industrial Melanism evidence for natural selection?
-Ben
The DNA thing. Yes, Dna has been tested and widely excepted as reasoning that all species evolved from the same species. But I’m asking if there is proof undeniable that evolution exists as the only way animals on this planet can to be. If all animals evolved then we have a small problem. First, of course in earlier evolutions it was probably through asexual reproduction that the species gain new properties or advantages over the environment. Now also of course, we have evolution happening through heterosexual reproduction. Now if DNA is to be used as evidence then, shouldn’t we all be so inbred that we’re stupid as the dirt we came from? DNA analysts will tell that the diseases that come from inbreeding could have lead to the mutations needed to have evolution.
I will concede that evolution very may well be the very truth that creationist and evolutionists are looking for, but rules of probability give me one other argument: How did life get started on this planet anyway? Amino Acids and phosphates could not have come together and just Poof! there’s Life! I’ve seen the calculations for the probability of that happening and they’re so much of a long shot that the universe would have to expand and collapse several times for “chance” to happen.
And for all you creationist, Read Genesis closely, if you think about it God could very well use evolution to creat life.
Here’s a funny question to think about(Don’t Answer It! We got enough to talk about!)
If life never sprouted in the universe and no one could observe it, would it still be here?
Those calculations are all bunk, due to the fact that the simplifying assumptions necessary are completely unjustified. But let’s run with them for a second.
So suppose the probability of life emerging on earth is 6.02 * 10[sup]-23[/sup]. You know, a nice random number.
The reactions that led to life on earth had to take place in the sea. Let’s assume the reactions require enough space that in the primitive sea, there were only a million independent reaction sites. This is probably an absurdly low number, but I’m feeling nice tonight.
The reactions occurred quickly. Let’s slow them down a lot, and assume they would take a second. Let’s also assume independence (probably not unreasonable, as the actual reactions would occur much more quickly, in my non-chemist opinion). There are then approximately 3.15 * 10[sup]8[/sup] independent reaction sites per year.
Let’s look at a period of 1 million years. That leads to 3.15 * 10[sup]20[/sup] independent reaction sites.
We’re dealing with a binomial distribution here, so the expected number of spontaneous generations here is 3.15 * 10[sup]20[/sup] * 6.02 * [sup]-23[/sup], which is equal to a little under .02. Give it a hundred periods of a million years, and you’re almost guaranteed to see life. Twice.
Bear in mind this only considered reaction sites on earth. There were probably a lot more throughout the universe.
So I don’t place much stock in the creationist’s probability calculations. If anything, they’re a concession. For further reading, look here.
Thanx for the clarification.
I’ve always had the question: Why are humans theories based on probability and chance?
Memnojokasel Durinjio wrote:
Um … do you know why inbreeding among closely-related people tends to result in genetic diseases?
It’s called recessive traits. You see, nearly every one of the 30,000 genes in your body exists in pairs. you inherited one of the genes in each pair from your biological father, and the other gene in the pair from your biological mother. Now, there are several possible alleles that any one gene can have: the gene for eye color that you inherited from your father might be the “green eyes” allele, for example, while the gene for eye color that you inherited from your mother might be the “blue eyes” allele.
But if that’s the case, what color will your eyes be? Answer: they will be blue. Not green. Why? Because a Blue Eyes allele is dominant over a Green Eyes allele. The Green Eyes allele is recessive. If you have two Blue Eyes alleles, you will have blue eyes. If you have one Blue Eyes allele and one Green Eyes allele, you will still have blue eyes. You will only have green eyes if both of your eye-color genes carry the Green Eyes allele.
Now, think about all of the traits you have that make you special. Look at the shapes of your fingers. The color of your hair. Your tendency or non-tendency to catch colds. How rapidly or slowly you age. And all the other myriad things that differentiate you from the other 6 billion humans on the planet. These traits are controlled by your genes, which means that each of these traits has a pair of genes associated with it. (There are a few exceptions to this, such as hemophilia in men, but nearly all genetic traits are controlled by a pair of genes, one from mom and one from dad.) Odds are, if you’re an average person, a full one-quarter to one-half of all your genetic traits are controlled by a pair of genes in which one of the genes carries a dominant allele and the other carries a recessive allele.
Now, I’m sure you have a few recessive traits that are expressed, as do your parents, but most of the genetic deck you were dealt when you were born had enough dominant traits to mask all the other recessive traits you’re carrying. Imagine what would happen if you had been born with that enormous number of dominant traits of yours instead being the recessive variant. You’d be pretty bad off, wouldn’t you? Heck, you’d be pretty bad off if only one-fourth of your dominant-recessive gene pairs were recessive-recessive instead. It would be like the difference between getting one or two random mutations, and getting a whole flock of them – your chances of genetic disease would be pretty darned high.
Well, that’s what happens when closely-related people produce an offspring. The two parents have such similar genomes that the chances skyrocket of their baby receiving recessive-recessive pairs where both parents had dominant-recessive pairs before.
To put it in probability terms: If the blue-eyed and green-eyed alleles exist in equal numbers, evenly-distributed throughout the population, then if two random blue-eyed members of that population have a baby together, the chance the baby having green eyes is 1/6. If, on the other hand, the baby’s parents are not randomly chosen, but are in fact inbred in a family line with a history of green eyes, then even if the two parents both have blue eyes the chances of the baby being green-eyed are closer to 1/4.
Or to put it another way, on average, an inbred child will have (1/4 - 1/6), or 1/12, of its gene pairs be recessive-recessive, even if its parents both showed dominant traits for that same gene pair. 1/12 of 30000 gene pairs is 2500 genes! 2500 genes all expressing recessive traits that might show up one-at-a-time in a non-inbred population, but here are showing up all at once. It’s a wonder these inbred babies are only mentally retarded!
Memnojokasel Durinjio wrote:
Natural Selection is most emphatically not based on chance. (Mutation is, but natural selection isn’t.)
Oh, and the point of my inbreeding argument was this:
The biological parents have to be really closely related for inbreeding to be a factor. In a large population, with natural selection weeding out the severe misfits, there will be enough genetic diversity that the chances of two random parents both having a dominant-recessive pair of alleles on the same gene-pair are the same 1-in-4 you’d expect to get from random chance. Which is low enough odds that their offspring will probably not have a crippling number of expressed recessive traits.
Natural Selection is the one where you got a short necked gerafe and a long necked girafe and the trees are tall so the short one can’t get to it and dies, right? I got and argument, why’d the tree get taller? What this will lead to is that natural selection is affected by the environment and something can always change the environment. A meteor could come and change the world climate right now. The probility for a climate changing meteor is, what every 50,000 years? And then we got global warming thats environmental changing. What I’m getting at is that on it’s own probility isn’t there but it’s always affected directly or in-directly.
Nope, just as there is no proof undeniable that intervention by an Invisible Pink Unicorn is not the only way animals on this planet can to be. When you make statements that span all time and space in an infinite universe, like this one, then their will never be proof undeniable of anything. All you can do is look at the facts and go with the most likely theory.
This overlooks the fact that we don’t just spontaneously form a new species from one individual in one generation that can’t interbreed with it’s own relatives. Development of a new species takes millenia usually and during that entire time the same old genes from the same old population are flowing into the new mutaants and the mutant genes are flowing back out. A monkey didn’t just turn into an ape one day, a monkey got more ape-like and continued breeding with monkeys. Either the entire monkey population became more ape-like as a result of his genes being favoured, or all the non ape-monkeys were geographically isolated from the ape-momkeys. But there’s a huge period of time during which ape-monkey and ape were sharing genes. By the time the populations deviated enough to prevent crossfertilisation the new population would have had as many genes as the old.
That I don’t follow. Care to enlighten me on which genetic diseases cause spontaneous mutation?
very
Tracer,
I have to seriously question your equations. They completely ignore the breakdown rates of AA polymers in an aqueous environment which is going to be faster than the polymeristation rate.
You also overlook the fact that best guess is that life spontaneously arrived within 5 million years, not one hundred million.
Having said that I appreciate they were just back-of-the-envelope calculations, but sometimes oversimplification isn’t a good thing.
O.K. Gaspode, I was refering to the genes themselves not the deseases.
Anyway, you have all enlightened me to a thought.
So many variables, probabilties and the like that it would have to rage into the millions. All of which were used to produce the complexity of organisms and lifeforms that are on this planet today. I just have the idea that God had to have his hand in there somewhere.
Thanks for your input thoughts and calculations. You have all helped me a little bit in my understanding of evolution.
I plan on next to post a theory of mine on the possibility that there is no intelligent life forms live on any planets in “sphere of influence”. I’ll explain in the thread.