It looks like I'm having a little trouble getting the thread going in the right direction here, so I'm going to throw a few more questions out there. Also please take note that I'm aiming at a top down approach here and I would like to get at the specifics of the evidence as we get there.
What are the mechanisms behind TofE and how do they work?
The principle mechanisms of evolution are mutation and natural selection. Some other important mechanisms are sexual selection and genetic drift. Also gene flow. All of the latter are various means of selection.
Mutation (a change in the DNA) is the source of variation. The other mechanisms determine which variations will survive and come to be normal for the species.
Why is it that TofE is the most widely accepted theory on the origins of the species?
Because it is the only one that explains the evidence from many different sources and is able to predict new fruitful lines of inquiry with accuracy. A stunning example of successful prediction was shown in the recent finding of
Tiktaalik.
Tiktaalik is a very fish-like tetrapod which could be either an ancestor or a close relative of the ancestor of all terrestrial vertebrates.
Before Tiktaalik was discovered, scientists made three predictions, based on what we already knew about fossils that are transitional between fish and amphibians.
- There must have been a species transitional between the latest fish in the line between fish and amphibians and the earliest tetrapod we already knew of.
- This species must have lived at a certain period of time.
- This species must have lived in a certain environment which over time would have developed into a certain type of rock.
They then did a survey to find the requisite type of rock of the predicted age and explored it for fossils. And they found a fossil that met the predicted characteristics of the sort of transitional they were looking for. They called it
Tiktaalik roseae
What has been the most influential evidence supporting TofE up until now?
The most compelling evidence supporting the TofE today is the direct observation of evolution both within species and in the formation of new species. For several examples of this (not just finches, though they are the stars of the book) see
The Beak of the Finch by Jonathan Weiner.
Other than direct observation, I find the taxonomic evidence (the nested hierarchy) the most compelling. Especially since it is now supported by genetic as well as morphological evidence (and so is now often called the "twin-nested" hierarchy) But to understand why it is so compelling you need to understand something about classification and why nested hierarchies are so rare.
Darwin himself felt that the evidence from geographical distribution of species and from embryology was very compelling. An excellent recent book on the contribution of embryology to the understanding of evolution is
Endless Forms Most Beautiful by Sean B. Carroll.
You may be surprised that I haven't mentioned the fossil record. You may be even more surprised to learn that one of the principal proponents of evolution today (Richard Dawkins) considers the fossil record unnecessary to establish the truth of evolution. He makes this statement near the beginning of
The Ancestor's Tale. On the other hand he also asserts that if we had nothing but the fossil record, incomplete as it is and always will be, we could establish the fact of evolution from the fossil record alone.
Certainly the fossil record is far more complete than it was a century and a half ago, what with the Burgess Shale, the Ediacaran fossils and discoveries like Tiktaalik, not to mention the many hominid discoveries of the 20th century. And with all these discoveries, not a single find has been inconsistent with the TofE.