Quote:
Originally Posted by Brad
But not all genes are inherited as discrete units (e.g. blue vs brown eyes) but instead exist on a spectrum. The most common example of this is height. There is no single gene where allele A stands for "tall" and allele B for "short." (And how would you define "short" and "tall" anyway?) You don't end up with either a short or tall kid or even one with the average of the parents' heights. Instead height exists on a continuous spectrum, with over 50 genes contributing to its outcome, a very complex process that is still little understood. You could, factoring in outliers, have a child of basically any height. And while environment can influence height, the role it plays varies greatly. For example, 2 boys (not identical twins) born from the same parents, raised in the same environment, fed the same diet, could still grow up with great differences in height.
I say all that to say...perhaps human sexuality functions the same way as height. It's probably not a matter of A or B like eye color. Instead of a "gay gene," multiple genes may contribute varying degrees of influence into a person's final sexuality. And it's what type of information from one gene and how it interacts with the information from all the other genes that ultimately determines the final outcome, and perhaps that is how you end up with varying degrees of bisexuality. And if that is the case, then perhaps as in the example of height, environment actually plays a much smaller role than we may have once thought.
Eh, just my 2 cents on a Sunday morning.
Brad
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You've raised a good point which I often forget to mention (although my last post was already very long anyway) - different genes can give different phenotypes, but that doesn't mean that gene alone is responsible for the outcome. Think of it like a cake recipe - you can substitute yeast with salt, for example, which will result in a very different cake, but that doesn't mean the salt alone will generate the different cake! Only in the presence of the other ingredients can it produce a flat salty cake! So it's only meaningful to talk about phenotypic differences.
As for height and sexual orientation being analogous... I wouldn't favour this view so much, as with height it's seems embryologically easier to have various height differences. Basically height differences can be attributed to genes saying "this much of more of the same here" (it's more intuitive with, say, discrete sections of a millipede, where you could have genes saying "100 copies of the same here" in one millipede, and different genes saying "110 copies of the same here", but it's basically the same thing). To my knowledge there doesn't seem to be anything like genes saying "this much heterosexuality here" and "this much homosexuality there".
Of course you'll have to forgive my potential for being wrong about the second paragraph - as I keep disclaiming, I'm not a biologist. I just have a keen interest in evolutionary biology.