Science and Exploration

[dreadgeek]

Originally Posted by Hollylane

I haven't been on much lately, and I just saw this. I'm prone to being succinct in my answers Aj, even more so when I've just arrived home from work. So, I hope that my short answer helps.

Basically, I think that necessary evolution of plants and animals happens in its own time. It is probably my Native American side that recoils from tampering with plants and animals, and changing them by inserting proteins or anything else into them, that would not be possible through a natural evolutionary process or through selective processes.

If I can ask you one other follow-up, does that same feeling (I don't know what to call it when you say your Native American side) apply to editing *out* genes? I ask that in the context of the Huntington's chorea example I gave a few days ago. Since we know that any number of repeats above 35 is where things start to go badly and there is *no* benefit to having 39+ repeats of the CAG motif on chromosome 4, editing out all repeats above 35 would prevent people from a rather horrible disease. Are you saying that just as you don't think we should be changing genes except in the long, blind process (which, in my mind, is pretty wasteful) of selection that we shouldn't edit out genes even if doing so would save lives? I'm trying to understand where the line would get drawn.

If inserting genes in is, for lack of any better term, against nature isn't editing genes out also against nature? If we apply the standard consistently (i.e. don't insert anything and don't remove anything) then aren't we condemning people who could otherwise be saved? Admittedly, it is perfectly natural to die of Huntington's. I will not argue that somehow it is unnatural. There are lots of fates that are perfectly natural but that I am glad we can overrule. I'm not ready to condemn people to a horrible disease starting at 27 just because they have 50 repeats of a gene on chromosome 4. There's no evolutionary benefit to Huntington's disease. It is simply one of those things where nothing nature says it *can't* happen so it *does* happen.

So why on Earth does the motif continue to show up in a small portion of the population? Why hasn't it been selected out? Because by the time you reach your late 20s, in the environments in which we evolved, you've already likely had children. Any gene for a disease that can, if you'll excuse the term, hold its horses until *after* you've had at least one child will tend to be able to ride along with the rest of your genome. After you've passed your genes on at least once, nature really doesn't have much use for you. Another way of putting it is that genes that cause diseases that kill you before you have a chance to reproduce are selected out. So all of the low-hanging fruit, from the gene's point of view, was selected out hundreds of thousands or millions of years ago. The genes for diseases that we see tend to strike after your early twenties which, in the EEA (Environment of Evolutionary Adaptation) was well into the average person's reproductive career. So diseases like Alzheimer's and Huntington's and heart disease and high blood pressure are all back-loaded toward the end of one's reproductive career. A bunch of fifteen year old people dying is a net-loss from the gene's point of view, particularly in the EEA. A bunch of 45 year old people dying is zero-sum from the gene's point of view. By 45 you've already reproduced a few times, your oldest surviving children are, at that point, adults. From the point of view of nature, you're now superfluous. Thanks for playing. Nice of you to leave some genes around. You're expendable, your genes are not. That's nature for you.

So unless we intervene using technology (selective breeding in humans, needless to say, is a road we should not even contemplate going down) then we're pretty much signing the death warrants of any person unlucky enough to have 39+ repeats of the CAG motif on C-4. That's the natural way. I think we should veto nature because I think it is wrong vis a vis Huntington's.

Cheers
Aj