The End of Evolution By Means of Natural Selection

quote:

---

So I'm afraid I can't reply to what you said because I didn't read it. I'll just say that as long as both populations still have strict subsets of the alleles of the original parent population then they must, on a genetic basis, still be the same species. As I've said to Faith, there may arise physical or behavioral differences that prevent mating, but both populations would remain genetically compatible.

---

Percy,physical and behavioural differences that prevent reproduction of one group with another are sufficient to make them into different species, aren't they?I've been thinking about this in the context of dogs. I suspect (though I don't know) that the massive size variation in dogs is brought about by assortment of alleles rather than mutations. The biggest dogs and the smallest dogs are reproductively isolated from each other - they cannot mate and the small dogs could not bring a mixed puppy to term. Something similar in the wild would generate multiple species.Now, if there were a population with a continuum of sizes, then this issue wouldn't arise. But if the 'middle size' population were to disappear, it definitely would.Edited by Peepul, : No reason given.

quote:

---

It depends upon how you define species. I defined it genetically at the same time that I noted the potentially isolating effects of physical and behavioral differences.

---

If you define it genetically, then you are right apart from the kind of genetic incompatibility WK was talking about. But I think that makes the problem easier! It would be better to refute Faith's argument using the 'interbreeding populations' definition of species. Although there is no formal agreement to it, that's the most commonly used definition.Edited by Peepul, : No reason given.

quote:

---

This is the definition Faith is using

---

Sorry, I hadn't paid enough attention. At least she's made the argument easier!

quote:

---

I see what you're saying. But I think you're wrong in assuming that large dogs and small dogs can't mate. Yes, it is a physical barrier for a large male dog to impregnate a small female dog. And it is a physical barrier for a small female dog to carry a large dog offspring to term. But if you flip the genders reproduction is easily possible. Other than the fact that the large female dog would have to be laying down, is there any reason why a small male dog physically could not impregnate her? Is there any reason why the large female could not carry a small offspring to term?

​

My wife's old roommate had a rotweiller/dacshund mix. Rotweiller mother, dacshund father. The smaller father had minimal issues impregnating the larger mother and the larger mother had minimal issues carrying the pups to term. The dog grew to be larger than a dacshund but smaller than a rotweiller, a hybrid. A male dog from the litter could easily impregnate another female rotweiller or a female dachshund and then you would have fourth and fifth size variants.

​

Unless there is a mechanism that would create barriers for a large mother/small father combination then I don't think size could be the lone cause of a speciation event. ?

---

Very good points Misha.Do you think the same is true of the smallest and largest dogs, eg chihuahua and great dane? There I can see the logistics being a problem!

quote:

---

Bacteria are a cop-out and a mystification in a discussion with a nonscientist.

---

Faith,why do you say this?Many of our metabolic systems and capabilities are similar to bacteria - in fact the more we understand about them the more we find that systems in animals and plants are similar to bacterial ones.We share the same basic genetic code and translation mechanisms with them.Lenski's experiments, and many others, show that benefical mutations have occurred in bacteria.Why are these beneficial mutations invalid in your eyes?Edited by Peepul, : No reason given.

All,this article seems to relate very well to the theme of this thread....Evidence for Pervasive Adaptive Protein Evolution in Wild Mice

quote:

---

We estimate that 57% of amino acid substitutions in murids have been driven by positive selection. Hominids, therefore, are exceptional in having low apparent levels of adaptive protein evolution. The high frequency of adaptive amino acid substitutions in wild mice is consistent with their large effective population size, leading to effective natural selection at the molecular level. Effective natural selection also manifests itself as a paucity of effectively neutral nonsynonymous mutations in M. m. castaneus compared to humans.

---

at Evidence for Pervasive Adaptive Protein Evolution in Wild Mice - PMCIn other words, the majority of amino acid changes that have occurred are adaptive.However, I can't understand this paper! Can anyone explain in simple terms what their methodology was and why it is valid?Edited by Peepul, : No reason given.