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Ok guys, what in your opinion is the BEST evidence for evolution? Is there one "slam-dunk, case closed, cincher" or is it a multitude of combined evidences?
Personally, I find the existence of endogenous retroviruses rather compelling.
It's complex, but a short recap: A retrovirus inserts its own DNA into the genome of the cells it takes over. At times, this happens in sperm or egg cells. If the host survives the infection, the retrovirus DNA sequence is inherited. Human DNA has 30000 sequences of the sort.
The interesting bit: A retrovirus sequence acts as a marker - once aquired, it is very unlikely to be erased again. And we can follow how the sequences are inherited and passed on as life branches out. For instance, we share some markers with chimps and gorillas, but not gibbons - indicating that the sequence was inserted after we branched off. What is more, no other animals carry those markers in their DNA.
The parsimonious assumption is that they've been aquired by some common ancestor shared by chimps, gorillas and humans - but not gibbons. Which matches the other scientific evidence for branching-off points that we have.
I am sorry if I am not communicating the point clearly, it is pretty complex - but it's damn hard to come up with a scientific hypothesis that better explains the evidence.
Modern DNA lineage mapping and tracking wins hands down. It shows past relationships and acts as a sort of timeline clock. We can see old bits of ancient viral particles, now unused, in our genes as well as the same stuff in chimp and ape and lemur DNA. It shows identical aging artifacts and identical attributes. Also, some of our unused DNA is just "temporarily out of service" because it's no longer needed. But it can and has been reactivated in the lab and then provides functions identical to that which WAS functional in older species.
Finally, it shows when breaks were made in the lineage, and then we go look for predictable evidence of that in the fossil record, coupled with independantly verified radioisotopic dating, and guess what?
It all coincides.
Now, this is either wildly coincidental "concoctionatin'" or, in fact, as Ockham would say, the most logical, simple and most straightforwad explanation is likely the right one.
Which is: we evolved from these prior lineages. and why, with such evidence, would we deny the obvious? I mean, if you really and simply just want to understand what happened, why fight all the evidence?
The other evidence lines, of an older and more speculative type, such as funtional morphology (as in, for example, skeletal structure evolution in transitional forms) placed in "most likely order of occurrence", and which has since been corroborated by isotopic dating and now DNA tracking, is just icing on the cake.
Cultural anthropology identifies artifact development to assert timing. Tool development, with the more modern, better designed, more functionally evolved tools found at shallower [i.e.: more recent, newer] depths in ancient caves, puts the final touch on this story, as it all comes together.
But that durned DNA stuff, which is really quite recent, is pretty hard to deny.
Oh, I forgot; it's also allowed Dr. Richard Lenski ("Dr. Evo") to document, in 2008, an actual speciation event after watching and evaluating the DNA of each succeeding generation of a species for an amazing 22 years. Now that's dedication, eh?
With the inerrant new techniques of DNA mapping, he could and did go back and evaluate each and every one of the generations he kept in the freezer, so that we could see the exact point at which a series of rapid genetic changes, tripped, as it were, by one key random genetic mutation, allowed the rapid differentiation of a new species that could accomplish something it's direct ancestor could not. And it passed it on to all subsequent generations.
And that, as they say, is the definition of a species. And of Evolution.
Hard to deny, unless you just "have to"...
(BTW, when taken in total, this is more than just "evidence" for Evolution. By all rational standards, it's Proof. The "evidence" against Evolution is, by comparison, real weak now, and has pretty much been routinely debunked at all levels. Such insightful responses to Lenski's spectacular experiment as "Oh yeah, well it's only a bacterium. I wanna see a cat turn into a dog overnight, ne-yah ne-yah!" really don't hold much water with mature minds.)
There is so much compelling evidence that it's difficult to single out one "slam dunk". My personal favorites are homeotic genes and how well they are conserved across species.
For the layperson, like myself, the easiest evidence to comprehend is that which I can see with my own eyes. If you have the chance to observe baby animals in the wild, you can see that some of them live and some of them die. Sometimes you can even see why some survive while others don't. Whether they're physically stronger/larger, or simply more aggressive at feeding time, some minute changes in an animal's genes sometimes allow them to be more fit for survival than their siblings. Granted, it's not nearly as dramatic as observing first hand a generation of bacteria changing into a new species before one's eyes, but it certainly helps to understand how natural selection works.
Tip: Binoculars are a great, affordable tool for those curious about nature.
I agree that there is literally so much evidence that it's hard to put into perspective precisely one simple thing. I'd say that one of the most useful discoveries in both studying and supporting evolution was and is probably what rifleman mentioned in his post in regards to DNA triangulation.
However, for me, the greatest probable evidence is actually the predictive power the theory of evolution has been able to muster - more specifically - Charles Darwin's almost prophetic insight.
To wit, Darwin knew nothing about genetics or DNA and probably knew very little about the fossil record in totality. I'm rather certain he didn't know about microbes, ocean sediments, or radioactivity.
Yet, Darwin was able to not only see that physiological change was the result of some "unknown variance" (what we call genetics today) but that it had perpetuated itself for millions of years - if his theory stood correct.
While Darwin's suggestions might seem primitive in light of the astounding amount of methods we've used to test for various kinds of evolution, his predictive powers are and were so accurate that if there is any one prophet that has ever lived I would be more inclined to saying that Darwin was much more so of that type than any deified holy prophet. To be able to literally put together a single theory that would rely on such a vast embodiment of evidential support to accurately accept it as valid truth and to be consistently proven right over and over again for the past 150 years is not only the trademark of genius but someone with Galapagos-sized balls.
While there have been discoveries across the whole range of the evolutionary spectrum, it's amazing to see how solidly and accurately one series of predictions 150 years ago could come true. That is, in essence, the very definition of prophecy, of insight, and of scientific truth, in my opinion. To be able to predict that not only did these things happen but that such a vast amount of supporting evidence would coincide with those predictions (even 150 years after one's death) is simply amazing.
"To be able to predict that not only did these things happen but that such a vast amount of supporting evidence would coincide with those predictions (even 150 years after one's death) is simply amazin"
That he could see the way it would all fit together, to me, constitutes all three of the miracles he would need for sainthood, " St. Charles the wanderer ", has a good ring to it, doncha think?
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