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"Omae o korusu..." - Heero Yuy

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"Ed Gruberman, you fail to grasp Ty Kwan Leap. Approach me, that you might see." -- The Master

http://www.geocities.com/stormlance/sealion.htm

I was WRONG.

Oh, I'm NOT wrong about how speciation occurs, or that Omega clearly doesn't understand the concept.

I was wrong about my source, though. I went home and looked through all my science books, and then realized to my great humiliation that the example I put forward did exist... hypothetically.

That is, the species that I THOUGHT proved my point was a speculative construct, not a real incident.

So I screwed up MAJORLY on that bit.
Sorry, My fault, I apologize. Sometimes it's NOT helpful to remember everything you come across... when you don't remember WHERE you came across it.

(**NOTE**) This does NOT preclude the possibility that an example exists elsewhere, and I just haven't found it yet.

In any case, I'd like to take this opportunity to use another analogy.

Species evolve like languages.
Latin, a parent language, became French, Italian, and Spanish. Similar, but clearly distinct. Languages evolve by the same mechanisms as species.

Start with group A and B.
Both speak the same language.
Now separate them. Put some kind of barrier between them (like the Pyrenees) and see that there's little cross-group mixing.
Leave Group A alone.
Now, introduce a new word into the language of group B. (Instead of 'pen', we'll call it 'frindle!') Let it spread throughout the population of B.
Now everybody in B says 'frindle.' They all still understand each other.
Now introduce another word. "Zarg" for Cat, or something. Allow it to spread in the same manner.
Repeat the process several thousand times.

You will find that the languages of A and B now difer considerably. Enough that people from A cannot now be understood by people from B, and vice-versa. BUT, at no point could the people of B NOT understand each other, as they ALL evolved at the same time. There was no point at which some one 'mutated' individual in group B was TOO different to the others to be understood.

THAT is how it happens, kids.

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"My knowledge and experience far exceeds your own, by, oh, about a BILLION times!" -- Q

But it's not so much a case of words being introduced (In most modern lanuages, "modern" words, such as, oh "internet", or "computer", tend to be rather similar, even in disparate languages, simply because everyone was talking to each other when the words were invented. But I digress).

In most cases, the words have "evolved" over time. So the word "flonty" might have, in one country, become "flonky,", "dronky", "donkey". Whereas another language might have gone "flonty," "fronty", "monty". They started from the same point, but over the passage of years, they ended up as different words.

Er, that made no sense. Ignore it.

There is the example of the horse and donkey though. They can interbreed, and produce an offspring. However, any offspring will be sterile, which is why they count as different species.

Rob:

A language isn't a gene pool. Your analogy is too simplistic. Regardless of whether it works in language or not, genetically, you can't have A==B, B==C, A!=C. It just doesn't work, because of the definition of species.

Under any circumstances, here's a question for you: what, exactly, makes a human incapable of genetic reproduction with a gorilla? What are the specific genetic differences that make it impossible? Then we'll have some idea of what'd have to mutate to cause a new species to evolve.

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"My knowledge and experience far exceeds your own, by, oh, about a BILLION times!" -- Q

Charles Darwin's Theory of Evolution.
1. Most animals produced large numbers of offspring. If they all survived there would be too many. The amount of adults stays constant. There is competition for the maintenance of like as resources are limited. There is a struggle for existence.
2. The individuals of a species and the offspring differ from each other slightly. Such differences could give them an advantage, therefore, they survive and reproduce. Survival of the fittest.
3. Organisms produce like organisms. Offspring have the same characteristics as the parents, so if the parent had an advantage, the offspring now have it. The Origin of Species.

Neo-Darwinism
Darwin - 1858
Mendel - 1865 Laws of Inheritance
DeVries - 1903 Mutations
Sutton - 1903 Link between gene transmission and chromosome behaviour in meiosis.

Evidence Supporting Evolution
1. Biogeography
The geographical distribution of species makes sense only in the context of evolution. Islands have many species of plants and animals that are endemic, yet they are closely related to species on the mainland of neighbouring islands. Two islands having very similar environments but positioned in different parts of the world will probably not be inhabited by closely related species, but will be closely related to species on the nearest mainland. This is because island species came or were brought to the island, and with the passage of time, they evolved differently due to their isolation. E.g. Where islands have arisen from separation from a mainland, their fauna can resemble fauna on the mainland, but differences arise which can only be explained by evolution. Snakes are common in Europe, present in Eastern England, rarer in Wales, and absent in Ireland. Isolated Irish fauna has marked similarities and differences from the Continental fauna. Endemic species to the island must have evolved from the original fauna after separation from the mainland took place.
Islands of volcanic origin (e.g. Galapagos) are completely devoid of life initially, but become inhabited by animals and plants. Though these plants and animals resemble the mainland species, they have differences, e.g. Giant tortoises and finches on the Galapagos islands. The species evolve to fill a particular niche in the habitat.

2. Fossil Record.
Most of the rocks that form the crust of the earth are arranged in layers. The oldest rocks form the lowest layers and the newest rocks form the top layers. Animals and plants have become embedded in sedimentary rock during it�s deposition. These fossils provide a record of the plants and animals of the past. The fossil records indicate that life has existed on the planet for about 4 billion years. Fossils show extinct animals and some of these extinct animals are transitional forms of living animals. The fossil record is not perfect due to improbable chance factors in the formation, endurance, exposure and discovery, of fossil species.

3. Taxonomy.
The fact that we can group animals according to their anatomical characteristics indicates that they have evolved from the same genus.

4. Comparative Anatomy.
The comparative study of the form and structure of animals and plants reveals that structures of the same embryonic state have different functions, e.g. use of limbs, but they are all composed of the same structural elements, indicating that they have evolved from a common ancestor. These elements are homologous structures.

5. Comparative embryology.
Closely related organisms go through similar stages in their embryonic development. All vertebrate embryos have gill slits during the early stage of embryonic development. At this early stage, embryos of all animals look similar. As development progresses, the embryos of different vertebrates become dissimilar, e.g. in fish, gill slits become gills, in mammals they have different functions. Comparative embryology indicates that evolution has taken place.

6. Molecular Biology.
Species that are judged to be closely related because of similar morphological characteristics will have similar DNA. The hereditary background of an organism is documented in the DNA which constitutes it�s genes and in it�s proteins, which are the products of genes. These genetic similarities indicate evolution from a common ancestor.

7. Populations evolve over time in response to selective forces in the environment.
Evolution occurs because of interaction between organisms and their environment. Evolution of a population is seen as a change in presence of certain characteristic traits over a succession of generations. E.g. Peppered moths ( Biston betularia), were speckled as camouflage with lichen- covered trees and rocks. In 1850 a dark, melanic form, named variety carbonaria, became more successful in industrial areas of England, where soot darkened walls, while the light variety remained more successful in the rural areas.

Definitions
Species - A species is a group of natural populations, which have the potential to interbreed to produce fertile offspring.

Gene Pool - Total aggregate of genes in a population at any one time. Consists of all of the alleles at all gene loci in all individuals of a population.

Alleles - Alternative versions of genes found on homologous chromosomes occupying similar loci but carrying contrasting inheritance factors.

Evolution may be described as the changes in the frequencies of the alleles over time. For example, in the peppered moth population living in the unpolluted region, the allele for light colour has a higher frequency in the population than the allele for dark colour, but in the industrialized areas, the allele for dark colour was more frequent. When alleles change frequency within gene pools accompanies by corresponding phenotypic changes (changes observable in the actual organism), evolution has occurred. Such a change in the gene pool is called microevolution.

Hardy- Weinberg Equilibrium. (Idealism)
The gene pool remains constant from generation to generation in sexually producing populations if :
1. The population is very large
2. The population is isolated
3. There are no mutations
4. Mating is random
5. All genotypes are equal in reproductive success.

The 5 potential agents of evolution are:
1. Genetic drift. In small populations, the death of individuals can significantly alter allele frequencies in the gene pool.

2. Gene Flow. Individuals with unusual allele frequencies may enter or leave the population.

3. Mutations are the original source of genetic variation that serves as raw material for natural selection.

4. Non-random mating. The choice of mating pairs is influenced by genotypes of individuals and is not governed by chance.

5. Genotypes are not equal in reproductive success. All individuals in a population are not equal in their ability to produce viable fertile offspring. This is natural selection. Alleles may be passed on to the next generation in numbers disproportionate in their frequencies in the present population.

HOW EVOLUTION OCCURS
Mutations are regarded as the raw material for evolutionary change. A mutation is the change of a gene from one allelic form to another. It is an inheritable change in the DNA sequence of a chromosome. Mutations are rare and occur by chance. A mutation that alters a protein enough to affect it�s function is more often harmful than beneficial. On rare occasions a mutant allele may outfit it�s bearer a little better to the environment. That individual reproduces and passes on it�s mutant gene to it�s offspring.
As a result of random mutations, dark peppered moths were present in an area dominated by light coloured moths before pollution darkened the landscape in industrial areas. The mutation became an advantage as the dark moths escaped the predatory birds.
Mutations are the source of new genes but they are very infrequent. Mutations are characteristic of populations.

THREE TYPES OF NATURAL SELECTION
Stabilizing - Extreme types are eliminated. For example, stabilizing selection keeps the majority of human births in the 3-4kg range. Infant mortality is greater for babies much smaller or larger than this.

Disruptive - Extreme types are selected. This occurs when environmental conditions favour the extreme types, e.g. in Cameroon there is a population of finches, black bellied seed crackers. Some individuals have small beaks, and they feed on soft seeds. Others have large beaks and feed by cracking hard seeds. Disruptive selection selects against intermediate types.

Directional - One of the extreme types is favoured, pushing the population along a particular path of evolution. Occurs during periods of environmental change.

Any factor that impedes two different species from producing fertile hybrids contributes to reproductive isolation.
(i) Prevent mating or fertilization.
-Populations do not meet
-Mating occurs at different times of the year
in each species
-No attraction between sexes
-Reproductive organs structurally incompatible

(ii) Prevent development of fertile adults
-Hybrid zygote fails to develop
-Hybrids fail to produce functional gametes
-Offspring of hybrids may have reduced
fertility

THE ORIGIN OF SPECIES
Two principle modes of speciation:
Allopatric speciation: May occur in geographically isolated populations, when a splinter population diverges in evolution from its parent population.

Sympatric speciation: (Plants). Occurs principally by a radical change in the genome which results in a sub-population becoming reproductively isolated in the midst of its parent population

The key event in speciation is genetic isolation

ADAPTIVE RADIATION
The emergence of numerous new species from a common ancestor introduced to an environment presenting a diversity of new opportunities and problems is called adaptive radiation.

Primitive Cursorial Land mammals ------> Aquatic (Whales & Dolphins)
Arboreal (Primates)
Aerial (Bats)
Subterranean ( Moles)

MACRO-EVOLUTION
Evolutionary change on a grand scale, encompassing the origin of:

• Novel designs
  
• Evolutionary trends
  
• Adaptive Radiation

• Mass extinction

It is a consequence of the interactions of organisms with their environments. An important event in the formation of higher groups is the appearance of an evolutionary novelty through:

(i) The gradual modification of an existing structure for a new function.
E.g. Birds may have evolved from agile bipedal reptiles. The wings and feather-like structures probably already functioned in netting insects for the fleet-footed reptiles. The initial flying may have been just a big hip in pursuit of prey or escape from predators, but natural selection would have allowed these feathered creatures to survive and reproduce. The wings and feathers were remodeled for flying.

(ii) A change in a regulatory gene. The development of an animal depends not only on structural genes but also on regulatory genes. The regulatory genes coordinate the activity of structural genes, guiding the rate and pattern of development. Each regulatory gene influences hundreds of structural genes. A mutation in a regulatory gene gives a larger result than a mutation in a structural gene.

A species may become extinct if it�s habitat has been destroyed. Therefore, extinction is inevitable in a changing world.

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*Kenshiro gets off bed made from solid stone*
*Bed made from solid stone explodes*
Fist of the North Star

You just don't seem to get it. There will be a clear dividing line in your model. One one side, you'll have people who can't reproduce with the rest of the population, and on the other, you'll have people who can. There's no middle ground. That dividing line is caused by a single mutation because it HAS TO BE. Otherwise, there wouldn't be such a clear division.

And you have yet to answer to my objection about having three groups that only sort-of constitute a species.

Hmm...that might make for a good skit.

"Well, it appears our argument is finally over. We've proved evolution is true."

"No you haven't!"

"What? Look, you silly person, you've got no pinkies left!"

"Yes I do."

"No you don't! And your skull is 13% larger."

"I've had a cold."

"A cold?!"

"Come on then, let's talk C decay! I'll pulverize you!"

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20th century, go to sleep.
--
R.E.M.
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Read chapters one and two of "Dirk Tungsten in...The Disappearing Planet"! Show no patience, tolerance, or restraint.

Perhaps your equation would make a bit more sense if you used the WAVY Equals sign (I don't know how to make it on here) which means "Is APPROXIMATELY equal to, but not exactly." I'll use a ~ to demonstrate.

A~B~C
A~B
B~C
BUT
A is not = C

Just as, on a grand scale, (pretend you're a 3-sequence code for a second)

aststtaststtatssst ~ atssttastttaatssst (5 degrees of difference)
atssttastttaatssst ~ stssttaatttaatssta (4 degrees of difference)

but aststtaststtatssst is not ~ stssttaatttaatssta (9 degrees of difference)

So that if the critical number of degrees for not-mateability is, say, SEVEN, the A+B species and the B+C species are close enough to reproduce together, but the A+C species are NOT.

Since only SINGLE degrees ocur with any one mutation, it never reaches the critical number WITHIN any group.

(Actually, though, the critical degree number must be MUCH higher, since every human offspring has about 100 single-bit mutations, and WE can all still reproduce, for the most part.)

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"My knowledge and experience far exceeds your own, by, oh, about a BILLION times!" -- Q

Why does anyone bother with Omega anymore? He's so jaded, naive and generally anything else that prevents a good rational argument about anything ever in the history of arguments ever.

You know what he's going to say, so why?

I don't know.