Wednesday, May 18, 2005

A Quick Note on Evolution and Homosexuality

I got another email the other day from a guy who wanted to challenge my beliefs. He wrote:
I know you hold Darwinist religious beliefs. Since you seem to think the desire to do certain stuff is a trait you're born with and since those who do that stuff don't tend to reproduce, doesn't your whole theory contradict the doctrine of natural selection. What I mean is, how is this trait passed on? Or is that desire just a very common mutation? Or maybe all those experts in those associations never considered that.

Ignoring the silliness about "Darwinist religious beliefs," let me say, I'm no evolutionary biologist, but I guess I have a thought or two on the subject.

Let's say, Darwinism can be looked at on at least two levels. At the level of the population, evolution is a change in the probability distribution of a phenotypic trait over time; change is usually seen as adaptation, though drift is possible, too, that is, random changes that do not affect fitness.

Evolution can also be looked at on the microscopic level. When we speak of genes for a trait, we mean patterns of DNA on the chromosome which function as a kind of developmental program for manifesting the traits biologically, almost always in conjunction with some environmental stimuli. Here we see evolution as change in the genotype, and it is possible that various genotypes produce similar phenotypes. For instance, human adaptations have arisen in both the Andes and in Kenya that allow individuals to run for a long time at high altitudes -- same phenotype -- but the genetic mechanisms are entirely different.

The PFOX types like to say "There is no gay gene." This is wrong in so many ways, it is hard to know where to start. First of all, there is no single gene for most complex traits. There is no introversion gene, no sense-of-humor gene, no musical gene ... Most human traits are supported by many, many locations on the chromosome interacting with one another, and interacting with the environment both in the deveopmental expression of the phenotype and in predisposing a response in the moment.

As I've reported here before, patterns on the chromosome have been found, which correlate with homosexuality. Patterns in the brain have been found, too, which are probably a function of development rather than learning. But to find a "gay gene," we would need to see a pattern that every gay person has, and no straight person, and that just ain't gonna happen. You will find parts of patterns here and there, and various combinations of those patterns which, combined with some environmental factors -- which can be hormones in the womb or childhood experiences or anything else, nobody knows for sure -- result in the person preferring partners of their same sex.

You see this nullifies the argument that it can't be inherited. Parts of patterns can be received from one parent and parts from the other, with neither parent having the entire combination of alleles that would make them gay (and we would really expect different patterns to work for males and females, meaning for instance that a female could carry the whole set of gay-male genes, with no effect). If there are many patterns with a similar effect -- and redundancy is an important feature of genetics -- then this becomes even more likely.

There's another thing, which is hard to grasp. As I mentioned, evolution can be seen to work at the level of the species or population. It is very common to find adaptations that are bad for the individual and good for the group. Just think of a male bird's bright colors, which serve the function of attracting mates, and also of attracting the attention of predators in order to lure them away from the nest. There is risk in that, and in fact some male birds are killed performing this stunt, but overall it is adaptive for the species.

I note that some persons seem to believe they have inside knowledge about what is "natural," or what God intended when He created certain things, but I tend to believe that God's true intent is mysterious, and that it is usually foolish to try to reason about how a trait increases the fitness of a species.

There is nothing contradictory about homosexuality being inherited.

12 Comments:

Anonymous Anonymous said...

Wow. You sound like SUCH an expert Jim. I never knew. Where did you get your medical and/or PHd degrees?

May 18, 2005 12:31 PM  
Blogger JimK said...

University of North Carolina, Chapel Hill.

May 18, 2005 1:02 PM  
Anonymous Anonymous said...

Which? And in what, may I ask?

May 18, 2005 3:33 PM  
Blogger JimK said...

Oh hey, I forgot the most relevant thing: social insects. Most ants, the workers, do not reproduce. Worker ants are the most numerous type, yet they neither lay eggs nor fertilize them. Evolutionary theorists aren't perturbed by that, in fact they think it is really really cool.

May 18, 2005 4:33 PM  
Anonymous Anonymous said...

You have avoided the question Jim.

May 18, 2005 9:11 PM  
Blogger JimK said...

I'm not here to talk about my personal life, my personal opinions, my personal feelings, or anything else about me. I cross that line a little last week, out of self-defense, but don't think it is wise or necessary. "Vigilance" is about the MCPS health curriculum, not me.

May 18, 2005 9:32 PM  
Blogger andrear said...

And you, anon- where is your degree from and in what? And by the way, is your real name Anonymous- is that what was on your degree?

May 19, 2005 8:17 AM  
Anonymous Anonymous said...

My degree it matters not. Jim is the one who claims to have all the answers. I am a mere parent is all.

May 22, 2005 7:59 PM  
Blogger JimK said...

Please point me to the place where I "claim to have all the answers." I will be happy to apologize for making that claim, once you refresh my memory.

May 22, 2005 9:49 PM  
Anonymous Anonymous said...

thanks for spelling it out soo beautifully.. i couldnot have agreed more..

July 26, 2007 1:12 PM  
Anonymous Jaxor said...

Anonymous....JimK is responding to an email he received. He is not claiming that what he says is 100% correct and everyone else is wrong. It is his opinion that he is expressing in rebuttal to a query. His qualifications in the area are irrelevant as no claim to authority is being made in his writing.

October 07, 2007 12:44 AM  
Anonymous Anonymous said...

Lol, what an ignorant tool this "anonymous" is. The whole point of blogging is to share what you know and what you believe as well as your opinion on the matters you're speaking of. Who cares where he went to school and what degree he recieved. Btw, UNC is a wonderful school, chapel hill is a beautiful place, I live 45 mins from it. Absolutely love it there. In "Gone to Carolina in my mind", James Taylor isn't just talking about North Carolina - he's talking about CHAPEL HILL. Most definitely deserved that song. I liked your view on the matter, and thank you for sharing that information with me. Even though I'm about 5 years late in commenting, LOL!

July 28, 2010 6:40 AM  

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