The Role of Isolation in Speciation

AnEmpiricalAgnostic · #1 7th July 2005, 03:32 PM

It seems that there is a reoccurring theme in the misunderstanding of our resident religious fundamentalists. All too often do I see ignorant posts such as:

Originally Posted by Carico

This is how humans came to be. There once was a primate (although it hasn't been described so it's called a common ancestor) who mated with another primate & together they didn't reproduce themselves but instead, something a little superior to themselves.

Originally Posted by Carico

Have you ever seen two apes breed anything other than apes?

Originally Posted by Carico

So how did apes produce human beings? "over time" explains nothing. It does not explain how 2 apes can produce a "homonid".

Originally Posted by Carico

So then why hasn't any species produced offspring as different from themselves as a homonid is from its parents in recorded history?

I’m not trying to pick only on Carico as there are many more literalists that say things along these lines, but Carico has been the major contributor lately.

Allopatric Speciation: the Role of Isolation in Speciation:

The formation of two or more species often (some workers think always!) requires geographical isolation of subpopulations of the species. Only then can natural selection or perhaps genetic drift produce distinctive gene pools. It is no accident that the various races (or "subspecies") of animals almost never occupy the same territory. Their distribution is allopatric ("other country").

A species doesn’t give birth to another species. This has never been claimed by the ToE. When species are isolated from interbreeding then small mutations eventually add up over time to create a dissimilar population. Given enough time and mutations, the isolated populations will not be able to interbreed any more and will have become an official new species. Why is this so hard to comprehend?

Isolating Mechanisms
What might keep two subpopulations from interbreeding when reunited geographically? There are several mechanisms.

Prezygotic Isolating Mechanisms
These act before fertilization occurs.

Failure to elicit mating behavior. On Floreana, Camarhynchus psittacula has a longer beak than Camarhynchus pauper, and the Grants have demonstrated that beak size is an important criterion by which Darwin's finches choose their mates.

Two subpopulations may occupy different habitats in the same area and thus fail to meet at breeding time.

In plants, a shift in the time of flowering can prevent pollination between the two subpopulations.

Structural differences in the sex organs may become an isolating mechanism.

The sperm may fail to reach or fuse with the egg.

Postzygotic Isolating Mechanisms

These act even if fertilization does occur.

Even if a zygote is formed, genetic differences may have become so great that the resulting hybrids are less viable or less fertile than the parental types. The sterile mule produced by mating a horse with a donkey is an example.

Sterility in the males produced by hybridization is more common than in females. In fact, it is the most common postzygotic isolating mechanism.

When Drosophila melanogaster attempts to mate with its relative Drosophila simulans, no viable males are even produced. Mutations in a single gene (encoding a component of the nuclear pore complex) are responsible.

This is also why we most likely aren’t going to see an entirely new species of humans evolve today. We’ve occupied every part of the globe. There is really no way to isolate one group of H. s. Sapiens from another. Maybe if a group of humand ventures off one day to colonize another planet and get lost for many millions of years will we speciate once again. The closes thing we have as an example today is some isolated tribes like the aborigines.

Originally Posted by Wortman

In evolutionary terms, it's a blink of an eye. Aboriginal people have been transformed over a hundred years or 200 years, very few numbers of generations, from a completely different way of life to what we experience today, and diet has dramatically changed for that population," he says. "And that very small period of time, there's no possible way their physiology could evolve to cope with such a big change in something like diet

Their isolation has not allowed them to evolve to handle the kinds of refined foods the rest of the world has. It is apparent in their alarming increase in diabetes now that they have come in contact with the rest of the population. If the members less tolerant to the kinds of foods readily available die off then only the members better equipped to handle refined foods will survive to breed. After time, the aborigines will blend back into the population and speciation will be prevented. However, this shows that, because of their isolation, they were on they way to becoming a divergent species of H. s. Sapiens. All it would have taken was time and more mutations.

SOURCES:

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/S/Speciation.html

http://www.cbc.ca/news/background/food/foodstories.html

AnEmpiricalAgnostic · #2 8th July 2005, 01:01 PM

Originally Posted by PaleHorse

I've not seen a bird come from a fish. Fish produce fish, dogs produce dogs, humans produce humans; show me the offspring of two cats not being a type of cat and then you got me.

I think every time I see this I’m going to add it and bump the post. Feel free to add any examples I miss.

Lilandra · #3 8th July 2005, 01:13 PM

Originally Posted by Uphill Battle

oh, good, so, they share charactaristics, that makes them all whales, eh? and where does it show them going from one form to another? Do you see housecats evoloving to cheetahs? It certainly would be a benefit, wouldn't you say?

Please, show me these other mutations. the gene one doesn't cut it, it looks more like isolation of a latent gene.

"Show me these other mutations"

JimmyKoKoPop · #4 8th July 2005, 05:00 PM

Given enough time and mutations, the isolated populations will not be able to interbreed any more and will have become an official new species.

Heh, but then you've got the headache (for taxonomists especially) of canines

gluadys · #5 9th July 2005, 03:17 AM

Originally Posted by JimmyKoKoPop

Heh, but then you've got the headache (for taxonomists especially) of canines
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If you are speaking of domesticated dogs, they have never been fully isolated from each other. Some have suggested that they have been isolated enough to be classified as four species though. Many breeds cannot mate successfully with other breeds at (for example) the opposite end of the size spectrum.

And there are wild canines too. Dogs are not the only members of the dog family.

AnEmpiricalAgnostic · #6 9th July 2005, 05:45 PM

Originally Posted by GodsSamus

Macroevolution: Change from one animal ex. a bacteria into another animal ex. fish

And another...

JimmyKoKoPop · #7 10th July 2005, 08:41 PM

Originally Posted by gluadys

If you are speaking of domesticated dogs, they have never been fully isolated from each other. Some have suggested that they have been isolated enough to be classified as four species though. Many breeds cannot mate successfully with other breeds at (for example) the opposite end of the size spectrum.

And there are wild canines too. Dogs are not the only members of the dog family.

I wasn't talking about just domesticated dogs, but canines in general - coyotes, foxes, wolves, and dogs. Dogs are often classified as a subspecies of wolf now, for instance. Some seperate species can interbreed and produce successful offspring, though most *will not* under normal circumstances (red wolves and coyotes have been known to interbreed. Coyotes and wolves have as well). There are also a couple of species that are considered by some to be hybrids.

ChrisS · #8 10th July 2005, 08:49 PM

When a creationist uses the term species, it usually doesn't mean species. What they mean is like a primate evolving into something that isn't a primate. However evolution never predicts primates becoming anything other than primates, therefore this is really just a misconception on the creationist's part, something that we can correct if were kind about it.

This is why, right now, it isn't wise for a creationist to get their information from a computer, but instead from a bioology class. It's not that hard to be a creationist once you understand this.