Scientists solve mystery of Scotland's shrinking sheep

[HAL 9000 96]

The shrinking sheep is all Scandal's fault.

scandal washed them in hot water?

Well you know Thanti is arriving tomorrow. He figured if they were smaller, he could hide MORE of them in the shed so Thanti wouldn't find them.

so that's what he's been up to!

I see my reputation precedes me I hadn't even posted on this thread, and yet I seem to be mentioned repeatedly here.

Yes, the sheep are safely tucked away in the shed. My plan is to sneak out at night to entertain them while Thanti is watching Thai soap operas on TV.

ALC raises a real question, that was not taken seriously. What is the most complex organism observed to show evolutionary change within a humanly-observable period? (I've paraphrased, but that was the gist).

I recently read two very good books on evolution - "Why Evolution is True", Jerry Coyne and "Your Inner Fish", Neil Shubin.

In the former book, there is a chapter on speciation - the process by which a single species splits into two separate gene pools which do not interbreed. Typically it is caused in the wild by having a geographic barrier (mountain range, ocean, etc) which suddenly splits a population in two. Each group evolves in distinct trajectories through random mutations in their gene pools over many generations until eventually they are distinct, and even when recombined are unable/unwilling to mate.

Here is a quote from Coyne's book, relevant to ALC's question:

What about the critical idea that reproductive barriers are the by-product of evolutionary change? That, at least, can be tested in the laboratory. Biologists do this by performing selection experiments, forcing animals or plants to adapt through evolution to different environments. This is a model of what happens when isolated natural populations encounter different habitats. After a period of adaptation, the different "populations" are tested in the lab to see if they've evolved reproductive barriers. Since these experiments take place over tens to dozens of generations, while speciation in the wild takes thousands of generations, we can't expect to see the origin of full species. But we should occasionally see the beginnings of reproductive isolation.

Surprisingly, even these short-duration experiments quite often produce genetic barriers. More than half of these studies (there are about twenty of them, all done on flies because of their short generation time) give a positive result, often showing reproductive isolation between populations within a year after selection begins. Most often, adaptation to different "environments" (different types of food, for example, or the ability to move up versus down in a vertical maze) results in mating discrimination between the populations. We're not sure exactly what traits the populations use to discriminate against each other, but the evolution of genetic barriers in such a short time confirms a key prediction of geographic speciation.

So ALC, at least to the complexity of fruit flies, there are laboratory measurements of visible evolutionary change.

I won't comment MC's original article, other than to say I too am suspicious that natural selection in a mammalian sheep population can cause any observable change within a human lifetime.

Now, sexual fetishism within a mammalian sheep population --- that might be occurring in my shed as we speak!!!!!

You guys are trying to have a serious discussion about sheep?? Here in off topic?? Now I've heard it all. You wanna talk about sheep? Head on over to the chopfvck thread.

Serious .... and not quite so serious , all at the same time!

ALC was hitting the artificial selection phenomenon... not actual genetic evolution that changes species altogether as is represented in lab experiments. Those changes present in the article quoted by MC's sheep... are not examples of evolutionary changes but manifestations or adaptations due to the capability for adaptation- be it beneficial or not to the population in question... as a result of the process of evolution.

As to the excellent reads you quote- yup... speciation is quite labor intensive (friend of mine from the university is in Africa right now collecting new fly breeders for more speciation experiments back here) work in flies but the development of these genetic barriers (mainly, protein/immune barriers to the sperm/oocyte fertilization reaction) can actually be reversed by selective means as well. I remember one undergrad genetics class where we selected for this despeciated flies and it was pretty cool seeing how two isolated populations were able to merge and produce viable offspring during the semester.

Anyway... the entire premise rocks. Hope you're having a scandalous time.

[HAL 9000 96]

{In other words, the adaptive mechanism is a response to an environmental stimulus... mainly... GLOBAL WARMING and its effects upon their habitat, food availability, and physiological state.}

[ScottThuy 140]

mmmmmmmmmmmmmmm Sheeeeeeeeeeeeeepppppp....