How has evolution been observed and tested?

Question

I was reading something a college professor (who is also a paleontologist) posted on his website. He said, "Evolution is an observable and testable fact whose predictions have been repeatedly corroborated." If you will, please help me understand this better. According to my understanding of evolution, it takes many, many years for changes to occur, so how can anything be observed?

Please only answer this question if you can keep your emotions under control. I say this because many people seem to get very upset or otherwise excited when they talk about this subject. Notice I have placed this question in the Science category and not the Religion and Spirituality one. I am purposefully trying to avoid a debate. If you are a creationist, please do not respond to my question to tell me what you believe in. I am fairly well versed in creationist viewpoints, so there isn't any need for your responses, thanks.

Answer 1

Evolution can be observed on a smaller time scale when disease-causing bacteria adapt to new treatments, or domestic animals are bred for a particular trait. It is not, however, a fact, it is a theory. A fact is a single piece of evidence, whereas a theory unites those facts. It's supported by a preponderance of evidence, but the professor your quoting was using the term "fact" somewhat losely.

Relativity is a theory, but every experiment that's been done to test it has produced the results consistent with the theory, so it's pretty unlikely that it's wrong. Same idea with evolution. We can predict the outcomes of certain experiments using rapidly reproducing organisms, or predict the existence of certain species (or fossil evidence of species), and then confirm these predictions. The fact that all available evidence is consistent with the theory (and there's a lot of available evidence), and nothing has been found to contract it is reason enough to treat it as fact for most purposes.

Science is not about finding a single piece of evidence to conclusively prove a theory. It's about constructing theories to fit the existing evidence and gathering new evidence that supports or refutes existing theories. Evolution is supported by a preponderance of evidence. While no one point conclusively proves it, when all the evidence is considered in the context of existing scientific knowledge evolution is a well substantiated theory. Intelligent design is not. What follows are brief explanations of some of the evidence that supports the theory of evolution.

1. Vestigial structures

One example of a vestigial structure in humans is the appendix. It has no function. Removing it is harmful only in so far as any surgery is associated with certain risks (so I wouldn't have it removed just for fun, but it's because of the surgery not the absence of the appendix). An appendix is found in several mammals. In humans it is small and has no known function. In rabbits and many other herbivores it is large and is used in the digestion of cellulose.

Another vestigial structure is the 5th pharyngeal pouch. Pharyngeal pouches are structures that arise during early embryonic development. They form the gills in fish. In humans, the make the bones of the inner ears, and a couple other things. In some species, they make the lower jaw, among other things. Anyhow, all species have them. All species have exactly six. In humans, the 5th one is quite small and doesn't do anything, but it is there, and then disappears. Developmental biologists agree, it has no function in humans.

2. Microevolution can be observed in both a controlled laboratory setting and in nature.

Creationists will tell you that microevolution does not prove macroevolution. This is true. However, it does provide evidence that macroevolution may be possible. Taken in the context of the other evidence for evolution, microevolution provides a mechanism by which macroevolution could occur. On its own, it doesn't prove that macroevolution occurs, but it does suggest that it is possible.

3. The fossil record.

Although the fossil record does not provide a “complete” record as fossils form only under certain conditions, it does show a gradual change in the morphology of species as well as numerous extinct species. There are a number of methods used to date fossils, and the time period from which a fossil comes can be determined with reasonable accuracy.

In vertebrates, there are two main types of jaw bones. One arises from one of the pharyngeal pouches (I don't remember which one), and the other arises de novo at some point during development. In adult animals, the two types are distinguished by the type of joint that connects the upper and lower jaw bones. All existent species of vertebrate have either one or the other. However, there's actually an extinct species that has jaws with two joints, one of each type.

4. Imperfect structures (the blind spot of the mammalian eye, for example).

I want to mention the bind-spot of the mammalian eye specifically because creationists often hold up the human eye up as an example of something that is too perfect to occur by "chance" (i.e. as the result of the natural selection of beneficial changes among random mutations).

There are also numerous examples where the morphology of a species is constrained by similar patterns in its ancestors (quadrupeds, vertebrates, etc.).

5. Developmental biology reflects evolutionary lineage.

Creationists like to bring up a man named Haeckel in response to this argument. Haeckel suggested that development reflects evolutionary origin. It was later discovered that several of the sketches he used as evidence over-exaggerated certain features, and some were of different embryos all together. However, many of his sketches do accurately reflect the morphology of the embryo. Haeckel's methods were sometimes wrong and his ethics were poor, but it just so happens that his theory turned out to be fairly accurate.

Any developmental biologist can tell you that embryos of related species show similar morphology in the early stages of development. The point at which their development begins to diverge shows a strong correlation with the relative point at which the evolution of the two species diverged. Human embryos look similar to chimpanzee embryos for a lot longer than they look similar to cat embryos, but all three develop similar structures in the early stages of development. The early embryos of humans, chimps, and cats are similar to each other but quite different from, say, a sea urchin embryo. This is based on photographs of actual embryos taken by respectable scientists, NOT on Haeckel's drawings.

I find it rather funny that creationists try to argue that because one scientist was a fraud we should disregard all of developmental biology.

6. Genetic analysis shows similarities among species reflecting evolutionary origins.

The main point here is that recent work has shown that the extent of genetic divergence among species is consistent with the expected separation based on the fossil record and morphological evidence. This supports the conclusions drawn from the other evidence.

Genetic analysis often reveals remnants of a gene that is functional in one species but not another (i.e. a mutation occurred that made the gene non-functional, but most of the sequence is still intact). Why would God have created non-functional sequences that are extremely similar to functional genes found in related species?

Also, non-coding regions of DNA show degrees of similarity that are consistent with the expected degree of evolutionary divergence. I understand how you could argue that God was essentially working form a common genetic template for all species, but why change the non-coding regions? These differences result from mutations that do not affect the phenotype of the species in any way but accumulate over time. Non-coding regions show sequences that are conserved with changes, and the number of changes is consistent with the number of mutations that would be expected to have occurred since the approximate time of existence of most recent common ancestor.

7. Homologous structures.

Homologous structures are structures that typically have similar morphological features and, often, similar functions, and are the result of evolutionary change of a single structure present in the most recent common ancestor of the two species. A homoplastic structure is one that may have a similar function and superficial appearance to another structure but is the result of convergent evolution (i.e. it was not present in the most recent common ancestry).

The most obvious examples of homoplastic structures are things like a human's hand and a gorilla's hand. A more subtle example is the human hand and the bat wing. Although the two structures clearly serve different functions, their bone structures are nearly identical. This is because the bat wing is a modified mammalian forelimb. In other word, the most recent common ancestor of the human and the bat was a mammal that had a forelimb with a bone structure similar to that of the modern human hand and other mammalian forelimbs. In humans this forelimb became the hand. In bats it became the wing.

An interesting example of homoplastic structures is the bird wing and the bat wing. Although the two structures clearly serve similar functions (i.e. flying), they are anatomically quite different. They have quite different bone structures and operate according to different mechanical mechanisms. In fact, the bat wing is structurally more similar to human hand than the bird wing. Incidentally, the bird and bat wings are homoplastic as wings but homologous as forelimbs.

That is just one example. The animal kingdom is littered with examples of structures that serve different functions but have extremely similar morphological traits, and structures that serve similar functions but show clear evidence of distinct evolutionary origin.

8. Many cellular and biochemical processes are conserved in a variety of species.

The point here is that virtually all cells utilize similar mechanisms of DNA replication and protein synthesis, share certain respiration pathways, and other biochemical processes. Related species show more similarities. For example, all plants are capable of photosynthesis, and utilize a virtually identical biochemical pathway to accomplish this. If you study cell biology you will find numerous examples of pathways that are common to different types of cells. I'm not going to go into this more here as it requires considerable background in cell biology. However, these biochemical similarities support they theory that all cells share a common ancestor.

9. Vestigial biochemical pathways (for example, pancreatic cells are light-sensitive even though they are located deep inside the body).

These are similar to vestigial structures at the cellular level. The specific example I mentioned is the light-sensitive behavior of pancreatic cells. Basically, the pancreas is located inside the body and will never be exposed to light. However, pancreatic cells grown in vitro (i.e. in a Petri dish, test tube, etc.) demonstrate light-sensitive activation of biochemical pathways similar to that seen in the cells that form the retina. There is no reason for this behavior unless this pathway is a remnant (i.e. a vestigial pathway) of a pathway present in an ancestral cell that did have come in contact with light.

There are many other examples of vestigial biochemical pathways. Like vestigial structures, their existence is easily explained by evolution but makes no sense in the context of creationism or "intelligent design."

Answer 2

It has been observed, and it has been tested. Anyone who tells you they have not doesn't actually know what they're talking about. And evolution doesn't have anything to do with origins, and never did. That's abiogenesis in the case of life - a completely different field of scientific inquiry, and a group of theories generally known as the "Big Bang" in the case of the origin of the universe. The Big Bang has nothing whatsoever to do with the study of biological evolution, and is generally studied by physicists, astronomers and cosmologists - not biologists. The reason Creationism is rejected is that it simply does not fit the evidence. UPDATE: Can you name a single measureable feature that humans possess that apes don't? There is no taxonomic way to define the group that includes apes and not also include humans. There's no way to observe an ape "become" a man because man is an ape. It's akin to observing an apple become a piece of fruit. Beyond that, even if a specific event wasn't observed, evidence of the event commensurate with observations made in other circumstances can be used to forensically reconstruct the event. Imagine a circumstance in which a body is found in a locked room with three bullets in its chest. Standing over the body is a man covered in blood spatters, holding a smoking gun with three bullets missing. There are gunpowder burns on the man's hands, and the striations on the bullets in the victim match the ones formed when the pistol the man is holding fires other bullets. The maid says she heard a loud sound, like a gunshot, coming from the room minutes before, and body temperature and lividity of the corpse are consistent with a very recent time of death. Two women overheard the man and the victim arguing ten minutes before the shot was heard. Now according to you, we have to let the man go because no one observed the event, and therefore we can't prove that he's the murderer. Not only that, but you claim that it's just as likely that the victim was killed 6000 years ago by a unicorn.

Answer 3

Evolution has been repeatedly "observed", but has only been tested in "thought experiments"; it becomes apparent to anyone who looks at the variations within orders, phyla & families that organisms must either have "branched" at certain points, or have suddenly "materialized". Since the latter requires a belief in "magic", it seems more reasonable to accept the mechanism of change, particularly since we have historical records showing that mankind has been able to partially "speciate" dogs (there used to be no Spaniels, and through selective breeding, we "created" Spaniels. Whilst Spaniels are not a unique "species", clearly they are a step in that direction.)

Only a fool would maintain that the power of a Supreme Being is what created Spaniels, ergo, "supernatural" influence is probably not necessary to explain why we have 13-spotted Ladybugs AND 9-spotted Ladybugs, Chimpanzees AND Belgians, etc...

Answer 4

When
I have looked into this and there seems to be more than one aspect of evolution. One aspect is called chemical evolution. This theory says that given enough time that dead chemicals can by chance arrange themselves into a living cell. When I have searched for scientific evidence of this I get things like this from wikipedia

"Abiogenesis remains a hypothesis, meaning it is the working assumption for scientists researching how life began. If it were proven false, then another line of thought would be used to modify or replace abiogenesis as a hypothesis. If test results provide sufficient support for acceptance, then that is the point at which it would become a theory.

I think your prof is wrong. It only has the status of a hypothesis. If he believes it to be true anyway then it is not science but a belief. I am not criticizing his belief but only asking why he calls it science.

Answer 5

We've observed micro-evolution in the lab -- feed fruit flies a mutagen, and some of the children will be different from their parents, and the new trait will breed true.

We've also observed intermediate evolution - the selection leading to breeds of dogs, corn.

We apply what we've seen from intermediate evolution to situations we observe on the isolated populations on islands; the classic case of that is Darwin's finches, of the Galapagos.

It's not a great leap from that to macroevolution.

Answer 6

Yes. Selective breeding is a type of evolution.

Dogs, Cattle, Racehorses, all have been changed by selective breeding. The only thing that it takes to take the step to natural evolution is to have a natural force make the selection.

When 2 Elk bulls fight to take control of the herd, they are making the natural selection for the next generation. The stronger bulls bloodline survives.

That animals change can be seen in the insect world. There is a moth in Britan that changed to a progressively darker shade of gray to better match the coal smoke colored environment.

Answer 7

Sure. To those who posed a false choice between evolution and creation. Why not both?

Suppose man was created using evolution as a tool? Everything works, except for some Bishop a few hundred years ago who decided the world was 6000 years old, using his own methods. Hardly a thing to be an immovable cornerstone of faith.

Here's a guy who thinks we were created - by starting a long process 13 billion years ago.

http://reasons.org/

Answer 8

You're right, evolution (goo to you) cannot be observed.
The study of origins (origins science) is different to operational science, and is not subject to the scientific method.

We can observe natural selection - sometimes called micro-evolution. Evolutionists postulate that given enough time this can give goo-to-you evolution. This is contrary to observation. Goo-to-you evolution requires an increase in genetic information. The proposed mechanism is mutations, however all observed mutations are information neutral of result in a loss of information.

Ideas about the past necessarily involve unprovable assumptions.

Check here for lots of articles on the subject.
http://www.creationontheweb.com/content/view/3033/

btw, the fossil record absolutely does not show evolution. It actually shows stasis and extinction. We find fossils allegedly millions of years old of animals identical to those alive today.
Darwin expected that lots of transitional fossils would be found. They have not. There are a handful of controversial ones.
The fossil record is strong evidence for creation and the flood.
http://www.creationontheweb.com/content/view/3001

Answer 9

If you want, give me your address and I will send you a book free.
" Did man get here by evolution or creation." Then you can make your mind
up your self.


Sincerely yours,

Fred M. Hunter
[e-mail]

Answer 10

It can be observed in the fossil record.you can test it by observing how animals adapt and change to survive in different environments