Evolution: The Scientific Evidence

[Zeta-Flux]

ewmayer,

2) Just because we don't know all the answers (nor even many of the question) doesn't require us to willy-nilly go about inventing magical agencies to fill in the gaps in our knowledge. Such just-so invention is the province of religion and spiritualism, not of science.

It is true I threw out my comment as a sort of joke concerning IDers. But note that I was not limiting myself to magical agencies (nor even supranormal agencies). I was also talking about us, mankind, in the ways we have affected genetics through "intelligent interference."

I appreciate your answers. I even appreciate your feelings concerning those who would force their religion on your science (which I'm not trying to do).

Best,
Zeta-Flux

P.S. While I personally am impartial as to IDism, I do think that the idea of "irreducible complexity" shouldn't be thrown out a priori. I think such questioning is healthy for the all involved, and that evolution shows its power when systems are shown not to be irreducibly complex.

[Zeta-Flux]

Prime95,

I'm sure such mathematical modeling could be done. On the other hand, is it worth it when, as ewmayer says, there is "no unambiguous evidence that points to a clear *genetic* (as opposed to developmental) cause for homosexuality"?

[jinydu]

Originally Posted by Prime95

That is a semi-plausible explanation. I suspect a gene would have to "work harder" to be passed on indirectly. That is, wouldn't a gene that increases an individual's survival rate by 10% have a better chance of passing itself on than a gene that increases your family's survival rate by 10% (or maybe not depending on the size of the family!)?

Indeed; I learned about this in a class I took. The phenomenon is called 'kin selection' and is governed by Hamilton's Rule (you can look up both terms). Basically, the fitness gain that an individual gets from helping a relative is equal to the coefficient of genetic relatedness multiplied by the fitness gain of the relative.

For full-siblings, the coefficient of genetic relatedness is 0.5
For parent/offspring, it is 0.5
For half-siblings, it is 0.25
etc.

[cheesehead]

A couple of quick notes:

Originally Posted by Zeta-Flux

(Wanted to add: As I understand it, IDers claim scientific evidence for their theory.

So? We've seen people post claims in this forum that they have mathematical proof of various rubbish. A claim is one thing. Actual evidence or proof is another.

For example, irreducible complexity.

... which has already been scientifically demolished.

BTW, this particular idea (irreducible complexity) turns out to be just another example of a logical fallacy -- the argument from incredulity. IOW, "if I can't imagine how it could be true, then it must be false". The flaw in that is that when someone else can imagine it, "poof" goes the supposed proof ... and that's exactly what's happened to so-called "irreducible complexity": other folks came along and showed how the complexity was, in reality, very reducible.

Did you try Googling on "irreducible complexity" and looking at the sites written by evolutionists instead of by creationists? Did you try http://www.talkorigins.org/, such as http://www.talkorigins.org/faqs/behe.html or http://www.talkorigins.org/indexcc/CI/CI102.html or http://www.talkorigins.org/faqs/behe/review.html or http://www.talkorigins.org/indexcc/CB/CB200.html?

- - -

Originally Posted by Prime95

One thing that has been perplexing me of late: homosexuality and evolution.

I hope no one in this discussion is committing the error of confusing homosexuality with infertility. Furthermore, I hope everyone in this discussion is aware that human sexual/affectional preferences span a wide spectrum and are not simplistically confined to a 100% "masculine" point and a 100% "feminine" point.

If my hopes are correct, then we won't see any more contention that homosexuality necessarily implies absence of descendents. It only takes one heterosexual act to create a descendent, and the other 99% of whatever-sexual acts are genetically irrelevant.

[cheesehead]

Originally Posted by Prime95

For example, take recessive gene diseases like

< snip >

sickle-cell anemia.

The sickle-cell trait is most common in people with ancestors who lived in malaria-prone regions. It has been found that the sickle-cell trait is a significant protection from malarial death.

So, while sickle-cell anemia is harmful and may sometimes kill, its lethality is significantly less than the lethality of malaria, and thus is evolutionarily beneficial to those living in malaria-prone regions.

Keep in mind that only a very, very few generations of humans have lived in modern conditions of medicine and sanitation or have routinely travelled far from ancestral homelands, and that we have a longer span between generations than 99.999% of other species. What might evolve in fruit flies during the career of a geneticist would take millennia to (naturally) evolve in humans. Almost all human evolution needs to be understood in the context of what is, to us, the distant past. That a genetic trait is harmful (or beneficial!) in modern conditions means almost nothing about the evolutionary past.

- - -

On a tangent: Young-Earth creationists are, therefore, handicapped in reasoning about evolution as long as they insist that Earth is no older than a few thousand years. Young-Earth creationism is not only a rejection of modern biology, but also a rejection of modern physics, because its rejection of radioactive dating is incompatible with sub-atomic physics. So, if creationism were to be allowed to be taught as science in school biology classes, the next intrusions would be in physics, paleontology, geology, archaeology ...

The long-term goal of creationism is not merely to adjust biology, but also to overturn the entire scientific method. The more that has been discovered by modern science, the more we've seen that all the various scientific specialities are interrelated and logically connected. It is not possible to throw out evolution without also throwing out all other science.

See "The Wedge Strategy" at http://www.antievolution.org/features/wedge.html.

[Prime95]

Originally Posted by cheesehead

If my hopes are correct, then we won't see any more contention that homosexuality necessarily implies absence of descendents.

The underlying assumption in the thread is that a homosexuality gene reduces the likelihood of direct offspring - although I certainly have no proof of that.

Let me ask a slightly different question: Assume that a gene is in 10% of the population. Assume that the gene reduces the chance of direct descendants by 15%. Assume the gene provides no other benefit. Would such a gene have been reduced to relative rarity over the millenia or could it maintain a 10% prevalence? I suspect such a gene would have become rare. If so, either homosexuality is not genetic or one or more of the assumptions is wrong.

Previous posters have argued for each of the three cases (homosexuality is not genetic, homosexuality doesn't diminish the chance of the gene being passed on, homosexuality provides some societal benefits). Evolution is definitely not my strong suit, the various explanations are quite interesting.

[cheesehead]

Originally Posted by cheesehead

See "The Wedge Strategy" at http://www.antievolution.org/features/wedge.html.

I really should not have posted that without warning you that "The Wedge Strategy" is a copy of a page that was posted on a creationist site (which tried to disavow that document after it was publicized by evolutionists), and that www.antievolution.org is a pro-evolution site despite its URL name.

[Jwb52z]

If homosexuality DOES reduce the likelyhood as has been mentioned here, it must not do it very much if the number of gay people having and raising children in the world is any indication. If I'm not mistaken, even though it's a small percentage of the planet, there are THOUSANDS of gay people who have children. I realize that they are sometimes adopted, but I've seen quite a number of men and women who are gay have their own genetic children as well. That should be evidence that the impulse to procreate is not simply a function that has to involve sexual attraction, right? Of course, this could all be crap because it's only relatively recently that people could have children without having sex.

[cheesehead]

Originally Posted by Prime95

Let me ask a slightly different question: Assume that a gene is in 10% of the population. Assume that the gene reduces the chance of direct descendants by 15%. Assume the gene provides no other benefit. Would such a gene have been reduced to relative rarity over the millenia or could it maintain a 10% prevalence? I suspect such a gene would have become rare. If so, either homosexuality is not genetic or one or more of the assumptions is wrong.

The latter. But the former is not necessarily 100% false.

"Assume the gene provides no other benefit." That's a pretty big assumption, one that takes that argument right out of the possibly-convincing category. Since we already know that some human traits are influenced by multiple genes, and that a single gene can influence multiple traits, speaking of "the gene" in relation to homosexuality is misleading. A few years ago one of the biggest surprises to come out of the sequencing of the human genome was the discovery that the number of human genes was only 30,000 or so, whereas most geneticists had predicted that the number surely was over 100,000, considering how complicated we are. IIRC, there are plants with more genes than we have. One lesson there was that genes interact with each other and can have multiple influences in combination.

There is significant evidence consistent with there being a genetic component in homosexuality, but that doesn't rule out non-genetic components. It doesn't have to be only one or the other.

Previous posters have argued for each of the three cases (homosexuality is not genetic, homosexuality doesn't diminish the chance of the gene being passed on, homosexuality provides some societal benefits). Evolution is definitely not my strong suit, the various explanations are quite interesting.

... especially when one throws in neglected cases such as, but not limited to, "homosexuality is partly genetic, partly non-genetic" and "homosexuality's influence on the chance of a gene being passed on is difficult to determine".

[cheesehead]

Originally Posted by Jwb52z

there are THOUSANDS

millions

of gay people who have

biological

children

from past or present opposite-sex marriages.

[Zeta-Flux]

cheesehead,

A couple of quick notes:

So? We've seen people post claims in this forum that they have mathematical proof of various rubbish. A claim is one thing. Actual evidence or proof is another

So? It is one thing to not give any credence to a teenage crank who posts nonsense. It is another to dismiss, out of hand, the claims of respected scientists who offers evidence which should, rightly, be examined (and considered evidence).

... which has already been scientifically demolished.

I thinketh thou dost jest.

First, your quotation of my sentence was taken completely out of context (literally--you gave no context for it). Even if the theory of irreducible complexity has been scientifically demolished (for the sake of argument) that only adds to the strength of the evolutionist position, which in my humble opinion, is something evolutions should be happy about.

Second, I think you have misunderstood the theory of irreducible complexity, if you believe it to be a logical fallacy. It certainly is not (as used by respected scientists). It also isn't a statement about incredulity. It is a precise statement that certain systems are unstable (or even dangerous) if certain mechanisms within them are even slightly changed. For example, I think it would be fair to say that a nuclear reactor is an irreducibly complex machine, created by an intelligent agent.

I'll go even further, and say the following: Not only is the theory that some machines in nature are irreducibly complex not "scientifically demolished" but we have *specific examples* of such machines. They have been created by us, humans. And, it certainly would NOT be a wise thing for any future race of intelligent beings to think that just because many machines in nature are not irreducibly complex that all of them are not irreducibly complex, and that none of them have been created by intelligence (when, in fact, there is evidence--provided at the very least by homo sapiens).

BTW, this particular idea (irreducible complexity) turns out to be just another example of a logical fallacy -- the argument from incredulity. IOW, "if I can't imagine how it could be true, then it must be false". The flaw in that is that when someone else can imagine it, "poof" goes the supposed proof ... and that's exactly what's happened to so-called "irreducible complexity": other folks came along and showed how the complexity was, in reality, very reducible.

First, as I demonstrated with a nuclear reactor (or, as some like to use, a stop-watch), there are many machines in nature which are irreducibly complex. You have misunderstood the idea if you believe it to be a logical fallacy. Second, you do not seem to be familiar with the arguments given for irreducible complexity if you have to characterize them with a straw-man version of "I can't imagine it otherwise" argument. Irreducible complexity is a statement about probabilities, as well as stability.

Did you try Googling on "irreducible complexity" and looking at the sites written by evolutionists instead of by creationists?

No, I did not try those sites. Firstly because I am not trying to defend any specific machine, nor any specific scientists theories. Secondly, I am more than happy for scientists to prove that many biological machines could have developed naturally over time. I find this a *good thing*.