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What specific experiments can be conducted to prove that evolution really happened?

I always hear that evolution is a fact, but have a lot of trouble finding examples of experiments that prove it. The peppered moth example that’s always given only demonstrates natural selection which is something that creationists accept. From everything I can gather, it seems like evolution is a hypothesis that can’t really be tested.

Posted: January 21st 2010

logicel

Common descent through modification is a fact because of overwhelming data from interlocking scientific disciplines. This fact is explained by the elegant scientific theory of evolution via natural selection because of the theory’s astounding potency in prediction and explanation.

However, if a different scientific theory replaces the evolution by natural selection one or if natural selection is discarded without another scientific theory taking its place, common descent through modification will remain as a fact because of the significant data supporting it.

It is not necessary to witness the fact to define it as fact. For example, we can’t go back in time and travel to the star whose light we see is being emitted even though it no longer exists. It is naive and ignorant to think science works just by direct observation of events happening in real time.

Posted: January 24th 2010

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SmartLX www

No, creationists do not accept natural selection in its entirety. Those who acknowledge it at all impose arbitrary limits on its capabilities, claiming that it can’t cause changes on the scale which is thought of (mostly by creationists) as “macro-evolution”.

In fact, there is no reason to suppose that natural selection, the primary drive of evolution, changes a creature so far and no further. As you say, natural selection on relatively small scales has been demonstrated conclusively, up to the level of speciation. Experiments demonstrating observable genusation, which would be necessary to move an animal between high-level (but poorly defined) Biblical “kinds” and qualify to all creationists as macro-evolution, are impractical within a human lifetime. However, there is no known barrier to the idea that changes such as we have observed, multiplied by thousands of generations over centuries, would make it happen. The burden is on creationists to find such a barrier.

Lesser-known research often provides better evidence than straight experiments anyway. The enormous similarity between the genomes of all living things tell us of a single common ancestor, and the differences of varying sizes tell us how far apart any two species are. Molecular biology, now that Richard Dawkins has sung its praises in The Greatest Show on Earth and Stephen Meyer has focused on it in Signature in the Cell, is suddenly at the forefront of the “debate”.

Posted: January 22nd 2010

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George Locke

I’d like to clear up one detail. The word “evolution” refers to two things, a fact about world history and a theory about the mechanisms shaping that history. Talk Origins explains this really well. “Evolution the fact” refers to the fossil and DNA records showing living things changing incrementally through history, with new traits deriving from old ones. These records combine to show that incremental change and speciation, i.e. evolution, is a fact.

“Evolution the theory” is the theory of evolution by natural selection. Living things collect and expend resources and produce offspring. The theory of evolution says that an organism that is more efficient at producing offspring will be more effective in spreading its genes. An example prediction of the theory says that new, efficient mutant may out-compete its neighbors so thoroughly that no neighbor without the mutation will survive.

Summing up: the fact is that living things evolve over time. The data which prove this are archaeological record. The theory is that evolution is caused by natural selection.

If you’re interested in the evidence for evolution, I strongly recommend you poke around the Talk Origins site. Their 29+ Evidences for Macroevolution page goes into detail about how we know the “fact of evolution”. If there’s something you find there that you don’t buy, or if you don’t find the answer to a specific question, we’ll do our best to help.

Posted: January 22nd 2010

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Blaise www

The theory of evolution is not as easily tested as most, simply because of the time-scales involved in watching it happen. Since by definition any interference in the process would no longer be natural selection, little can be done to hurry it along. That said, if you accept the existence of natural selection, you already accept evolution, so I assume the question you are really asking is “how can we do an experiment to prove it has been going on for billions of years, rather than for 6000 years, as creationists claim?”

Since we do not at this time have the technology to look backward in time, we cannot gather evidence of long term evolution by direct observation, but science gives us a loophole. By definition, a scientific theory makes specific predictions of what will happen in a given set of circumstances. Like a crime scene detective, if we can find evidence of those predictions having come true at some time in the past, we can treat that as evidence that the theory is right. It isn’t as reliable as setting up a controlled experiment and watching it happen, but if you consistently find the evidence that your theory predicted, over many thousands of cases, you can accept this as proof that the theory is correct. In the case of evolution, there is a mountain of evidence that matches the predictions made by the theory.

First, as you pointed out, speciation has been observed by scientists numerous times, in birds, insects, lizards, and bacteria, so we know what it looks like when it happens, and can predict what it would have looked like in the past.

Next, the theory of evolution predicts that since all life are cousins, the more closely related cousins should be more alike and have more similar DNA and biochemistry, while the most distant ones should be more different, and have less similar DNA and biochemistry. This means that even starting from a single cell of life, given billions of years of slow speciation, we should have an extremely complex biosphere, with incredibly diverse life forms that appear to form a relatively smooth continuum of shapes and biochemistries. In fact, we do find this.

Third, the theory predicts that there will be intermediate forms of creatures that connect ancestral species to later species. If this were true, you would expect to find intermediate species represented in the fossil record. In fact, hundreds of years of study of the fossil record has produced thousands of examples of intermediate species.

Fourth, evolution predicts that the fossil record, with all its intermediate species, will be sorted by age in the rocks they are found in. In fact, we also find this to be true.

Fifth, evolution predicts that since there is no specific goal or timetable to the process, we should see different rates of change in different organisms in different environments. A well adapted species in a stable environment could remain unchanged for millions or even billions of years, while one in a volatile environment could accumulate significant changes in a comparatively short time. In fact, there are hundreds of examples of this. Fossils show that creatures like crocodiles and sharks have remained nearly unchanged for millions of years, while animals in small, difficult island environments have been observed by scientists to gain noticeable changes during a single human lifetime.

Sixth, and most important to your question, while evolution itself contains no direct prediction of the time evolutionary changes will take, geology has dozens of methods for determining the age of rocks, based on things like sedimentary deposition rates, chemical makeup, tectonic activity, and several different kinds of radioactive decay dating, all of which agree with one another, and all of which date the fossil record to having covered billions of years.

Is any of this absolute proof? No, but the pile of evidence is huge and keeps getting bigger. Eventually, we have to accept that if it looks like a duck, walks like a duck, and quacks like a duck, thaere’s a pretty good chance it is a duck!

Posted: January 22nd 2010

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