Let’s get this over with shall we?
The theory of evolution, which is a collection of various hypotheses, laws, and sub theories is an explanation. It is an explanation that not only covers a wide range of observations, or ‘facts’ (another word for data), but allows us to predict other observations. It takes other theories, or explanations for indirectly related observations, and incorporates them into an explanation that covers a greater number of observations. As I’ve stated before, the power of a theory is in how it covers each of the observations in the context of each other. Each new observation, whether direct, indirect or trace narrows the number of possible explanations down to the one most probable.
Taking one particular observation and claiming it doesn’t prove the theory, as creationists do, is misguided, ignorant or blatantly dishonest. Take your pick.
The observations we make aren’t about a monkey giving birth to a human, as demanded by your average dollar store creationist, it’s all the things that lead up to a cohesive explanation.
What follows is a short limited example.
Observing geological stratification, floods, erosion, volcanic eruptions, plate tectonics, atomic decay chains, astrophysics, the speed of light, fossil ordering, even simple parallax tells us the Earth has been around for a long time and the universe even longer.
Looking at a flood by itself doesn’t inform us of old age, it simply tells us water flow can collect, move and deposit large amounts of material in a short time. Looking at that alone allows a number of explanations for the observed stratification, including but obviously not limited to a global flood. Volcanic eruptions give us another possible source for stratification, eg. massive simultaneous global eruptions. Again, this can be explained in a young Earth context. However, when we take a closer look at the layers the observation is that the volcanic and sedimentary layers are interlaced. This means sedimentary layers had to be deposited separately from the volcanic layers. This belies the idea of a single global flood and a single massive volcanic event.
Let’s take a look at erosion and we can see that different patterns and different rates of material removal occur with the different composition of the layers. We can also see that the age of the sedimentary layer, the longer it has been under compression from the weight of layers above it affects how quickly and deeply erosion leaves patterns.
These three observations – flood deposition, volcanic deposition and erosive wear from water and wind combine with the observed layer composition to tell us a complex system of events, occurring over a great deal of time formed the specific layering observed, eliminating a single one year long global flood as a possible explanation for the observations.
Even before Darwin formalized evolution by selection, and the recognition of common descent suggested by geographic arrangement of related species, the Earth was known to be much older than the 6,000 – 10,000 years claimed by Ussher and modern Young Earth Creationists (YEC).
If you add in fossil ordering, plate tectonics, the speed of light, parallax, modern astrophysics and atomic decay chains the only explanation for all those observations taken in context with each other is that the Earth is billions of years old and that the forms life took changed over an almost as long range of time.
There is a chain involved here. Newton’s comment “If I have seen further it is by standing on ye sholders of Giants” applies to theories. Observations lead to explanations which when viewed in relation to each other lead to more precise explanations by ruling out possibilities.
Those observations related to the Theory of Evolution are the changes in fossils, the order those changes are found in the strata, the similarities and the differences of traits found in extant organisms, the relation of DNA to the traits shown by extant organisms, the changes in traits correlating to changes in DNA, the pattern of similarities and differences found in DNA between extant organisms, the rate of DNA changes (mutations) found between generations of organisms and the non-random effects on the distribution of traits/DNA in populations of organisms by environmental selection. They can only be explained by one comprehensive collection of laws, hypotheses, and series of other theories with testable predictive power – the modern theory of evolution and development.
Because all of these observations can and do suggest predictive tests they are science. Because they’ve all been tested they can contribute to the convergence on a fully accurate explanation. Because they have increased the accuracy in the explanation the explanation can be used to explain other observations.
On the other hand, an all powerful, capricious god can explain everything, thereby being non-predictive and non-testable. It is not addressable by science so the claim by creationists that what they do is science is wrong.
This should be stressed. The Theory of Evolution is the explanation for the hundreds of observations that have been made in the natural sciences, and the hundreds of observations made in laboratories. Humans having a common ancestor with other apes is the best explanation for the observations.