Thursday, February 07, 2008

Selective stress-breeding to create a long-neck

Background: This system presumes that my theory is completely correct (I do). Artificial selection is all well and good and has a proven record of succeeding in breeding stock with desired characteristics. However, the characteristic in question must exist in the population to start with. This is highly unsatisfactory and there is just no way you could, say, breed an antelope with a considerably longer neck (or taller all round, like a giraffe) without triggering appropriate mutations first.

The trick would be to find the same stress/mutation trigger that caused (say for the giraffe) those mutations required to be more prevalent, which allowed natural selection to have something useful to select from and speciate a taller (long-neck) animal.

The first condition is to pick an animal that feeds on leaves. There is not much point picking a carnivore or a herbivore that only eats grass/fruit etc. because there is no natural situation in geologic history in which a long neck would be the difference between life and death for such. I choose the antelope in this case - it eats leaves and lives in the same continent, so might share the required triggers and responsive genetics.

The second condition is that the breeding stock must be in some kind of stress. This is considered animal cruelty, so I suggest any experiments are done in a subsaharan country that is in a state of war: Nobody notices any cruelty that happens in those countries. Stress is well known to trigger mutations and is highly necessary to accelerate the process of artificial selection.

The third condition is to pick a stressful situation appropriately. Adaptive mutations happen as a mutation response that succeeded in the geologic past. They may not be apparent in the animal because they eventually reversed in the normal cycle of things - hopefully numerous times in the species' history such that it reinforces the response(s). In the case of the antelope, the stressful situation might have these features:
1) Near-starvation. This is known to also have physiological responses of delaying maturity, among other things. It is likely to trigger responses that might achieve it more food for its progeny in analogous situation.

2) Declining and/or isolated population. This reinforces that it is likely to be a long term stress, and which migration is unlikely to resolve. Inbreeding and polygamy might be physiological indicators of this.

3) Visual cues that food is plentiful higher up. Perhaps just out of reach, or even selective cues like seeing that taller relatives are better fed.

4) A lack of predators. Predators are known to put selective pressure towards earlier maturity thus smaller form.

I don't know if penning up antelopes, while at the same time putting heaps of food just out of reach of all but the tallest is an ethical way to prove Lamarck right - But I think that is exactly the sort of thing that led to Giraffe's long necks, and could be demonstrated within the space of a few lifetimes.

8 comments:

Dr. Clam said...

You need to think of an experiment using a smaller animal with a shorter lifespan. YThis experimental plan is not very practical.

Dr. Clam said...

Seeing an opportunity to score a pedant point, you should either have "long neck" or "Long-neck".

The first would imply you were trying to lengthen the necks of these antelopes, the second convert them into a phenotype like the "Long-necks" of the Land Before Time films. :P

Dr. Clam said...

Hmm, actually you score a point, since "long-neck" is perfectly valid for the Land Before Time critters. Curses! :(

Marco said...

You need to think of an experiment using a smaller animal with a shorter lifespan. This experimental plan is not very practical.

One obvious and easy one is mice with darkness stress:

Control group 1 - No major stresses.

Control group 2 - stressed with a variety of stresses which specifically excludes unavoidable darkness.

Test group - Raised in complete darkness. Most importantly, forced to breed and eat in complete darkness.

Measure rates of genetic defects, especially those involving eyesight, as a percentage of each generation.

The problem with this experiment is that (even presuming success) it is likely to be viewed as an exception to the rule of mutations being random, rather than an example of a new rule in itself.

The giraffe neck example is so tied in with Lamarck, that success in that experiment is likely to see much of the orthodoxy won over.

Marco said...

Seeing an opportunity to score a pedant point, you should either have "long neck" or "Long-neck".

Yes, as you probably have guessed, I kept the ambiguity in there for facetiousness and for the evolutionary bent on the land before time series!

Chris Fellows said...

Hey, you should read "Genes" by Bernard Levin, the standard molecular biology text. I have edition 7 and will send it your way when I have finished re-reading it. You will like it. The real standard paradigm of Molecular Biology is so much more consistent with a picture of a bootstrapping genome "designing itself" than with the "selfish gene" vision you rail against.

Marco said...

Yes, thanks. I shall read it. After all it was reading "Panda's Thumb" which got me really going down this line (Chapter 7). I don't really know if I'll be satisfied until some UNE biology post-grad student is asked to do an experiment down this line (not with antelope, but with blinding mice)

Marco said...

so much more consistent with a picture of a bootstrapping genome "designing itself" than with the "selfish gene" vision you rail against.

On reflection I don't think you disagree with Marconomic principle 4 at all. It is your axiom of God being outside, separate to the universe and simple that I disagree with. I agree with you that the God I have in mind would not be worthy of praise Unless my assumption that for all intensive purposes my God is a close approximation of your God for everything that is important for humans on this Earth.