What exactly is the Theory of Evolution?

We get so many drive-by creationists trolling through here that it may be useful to define exactly what we mean by the theory of biological evolution. If there is something that should be added, subtracted, or modified to the executive summary below, feel free to do so.

The Theory of Evolution is meant to explain the Earth's current biological diversity and the historical diversity and change seen in the world's collection of fossils and genetic comparisons. The Theory is disarmingly simple. It is comprised of a few self-evident observations, some reasonable hypotheses, and some basic predictions.


Assumption

0. There exists an initial stock of life forms.

Observations

1. In a natural environment more individuals of a species are born than can possibly survive given the environment’s resources and the species’ predators.
2. Individuals of a species display variation in traits.
3. Individuals better adapted to the current environment leave more offspring than those which are less well adapted. This is called differential reproductive success.
4.There is a mechanism by which traits in the current generation are passed to the next generation and by which traits may change slightly.

Hypotheses
5. Assuming the species’ environment remains stable, over time the population will become dominated by individuals with the traits responsible for the differential reproductive success. This is called natural selection. If the environment changes significantly, then natural selection may favor a very different set of traits within the population.
6. A new species emerges when its traits are sufficiently different from the ancestor species such that members of the new species cannot or will not reproduce fertile offspring with the ancestor species. This is called speciation (there are other valid criteria for speciation).

Predictions
7. The individuals in the next generation of a species will have traits very, very similar to those of the current generation, but not identical to the current generation.
8. If a subset of a population becomes geographically isolated from the rest of the population, then the traits of the two groups will diverge more rapidly than if they were able to co-mingle. The more dissimilar the environments in the two locations, the more rapid the speciation will be.
9. At a given point in time, the species in one region will share more genetic and anatomical traits with species in neighboring areas than with species in more distant regions.
10. In a given region, the species in one epoch will share more genetic and anatomical traits with species in the preceding epoch than with species in earlier ones.
11. If species A and B share a recent common ancestor, then they will share more genetic and anatomical similarities than species A and C which share an older common ancestor.
12. All species alive today share a universal common ancestor.

There are more observations, hypotheses and predictions but I think these are the major ones. Note the Theory addresses neither the origin of the universe nor the origin of the first life forms.

Also note the Theory states what we should expect not to see in the natural world. For example, we should not expect to see drastically different creatures in adjacent epochs in the same geographic region. The dinosaurs of North America in the Cretaceous will not be vastly different from the ones of the Jurassic; and those of the Jurassic from the Triassic.

Nor across epochs would we expect to see related species scattered randomly in suitable environments, but migrate gradually from one region to the next. Instead, we find marsupials first in Africa and then in South America but before the continents split apart. Then we find them migrating to North America, but only after the land bridge in Panama formed.

By comparison, creationism and ID place no limits on the omnipotent Creator, who could presumably place any type of creature anywhere in the world at any time and for any reason. Neither approach gives us any glimmer of understanding of how the biological world works today or in the past.

We get so many drive-by creationists trolling through here that it may be useful to define exactly what we mean by the theory of biological evolution. If there is something that should be added, subtracted, or modified to the executive summary below, feel free to do so.

The Theory of Evolution is meant to explain the Earth's current biological diversity and the historical diversity and change seen in the world's collection of fossils and genetic comparisons. The Theory is disarmingly simple. It is comprised of a few self-evident observations, some reasonable hypotheses, and some basic predictions.


Assumption

0. There exists an initial stock of life forms.

Observations

1. In a natural environment more individuals of a species are born than can possibly survive given the environment’s resources and the species’ predators.
2. Individuals of a species display variation in traits.
3. Individuals better adapted to the current environment leave more offspring than those which are less well adapted. This is called differential reproductive success.
4.There is a mechanism by which traits in the current generation are passed to the next generation and by which traits may change slightly.

Hypotheses
5. Assuming the species’ environment remains stable, over time the population will become dominated by individuals with the traits responsible for the differential reproductive success. This is called natural selection. If the environment changes significantly, then natural selection may favor a very different set of traits within the population.
6. A new species emerges when its traits are sufficiently different from the ancestor species such that members of the new species cannot or will not reproduce fertile offspring with the ancestor species. This is called speciation (there are other valid criteria for speciation).

Predictions
7. The individuals in the next generation of a species will have traits very, very similar to those of the current generation, but not identical to the current generation.
8. If a subset of a population becomes geographically isolated from the rest of the population, then the traits of the two groups will diverge more rapidly than if they were able to co-mingle. The more dissimilar the environments in the two locations, the more rapid the speciation will be.
9. At a given point in time, the species in one region will share more genetic and anatomical traits with species in neighboring areas than with species in more distant regions.
10. In a given region, the species in one epoch will share more genetic and anatomical traits with species in the preceding epoch than with species in earlier ones.
11. If species A and B share a recent common ancestor, then they will share more genetic and anatomical similarities than species A and C which share an older common ancestor.
12. All species alive today share a universal common ancestor.

There are more observations, hypotheses and predictions but I think these are the major ones. Note the Theory addresses neither the origin of the universe nor the origin of the first life forms.

Also note the Theory states what we should expect not to see in the natural world. For example, we should not expect to see drastically different creatures in adjacent epochs in the same geographic region. The dinosaurs of North America in the Cretaceous will not be vastly different from the ones of the Jurassic; and those of the Jurassic from the Triassic.

Nor across epochs would we expect to see related species scattered randomly in suitable environments, but migrate gradually from one region to the next. Instead, we find marsupials first in Africa and then in South America but before the continents split apart. Then we find them migrating to North America, but only after the land bridge in Panama formed.

By comparison, creationism and ID place no limits on the omnipotent Creator, who could presumably place any type of creature anywhere in the world at any time and for any reason. Neither approach gives us any glimmer of understanding of how the biological world works today or in the past.

So how does this explain how humans came from apes? How did 2 apes produce offspring so drastically different from themselves as to be given a different name? Again, apes still breed apes & humans still breed humans. Some have blue eyes, some are tall, short, deformed, etc. Some apes are taller, shorter, deformed, etc, although there is less variance in ape offspring than in human offspring. So why would apes be prone to breed something called a "homonid"? And how are offspring better adapted if they still produce the same kinds of offspring they've always produced?

And how are offspring better adapted if they still produce the same kinds of offspring they've always produced?

So how does this explain how humans came from apes?

How did 2 apes produce offspring so drastically different from themselves as to be given a different name?

Again, apes still breed apes & humans still breed humans. Some have blue eyes, some are tall, short, deformed, etc. Some apes are taller, shorter, deformed, etc, although there is less variance in ape offspring than in human offspring.

So why would apes be prone to breed something called a "homonid"?

And how are offspring better adapted if they still produce the same kinds of offspring they've always produced?

So how does this explain how humans came from apes? How did 2 apes produce offspring so drastically different from themselves as to be given a different name? Again, apes still breed apes & humans still breed humans. Some have blue eyes, some are tall, short, deformed, etc. Some apes are taller, shorter, deformed, etc, although there is less variance in ape offspring than in human offspring. So why would apes be prone to breed something called a "homonid"? And how are offspring better adapted if they still produce the same kinds of offspring they've always produced?

How long have you been here that you're still honestly asking these questions?

Is this rocket science or something?

Individuals don't evolve - populations do.

And what is different about populations today than those thousands of years ago? There are still tall, short, blue-eyed, brown-eyed, deforemd people today just as there were thousands of years ago. In fact, humans are closer to annihilating themselves than ever before. So how have we evolved?