Observation & Evidence for Evolution - What We Observe of EvolutionCreationists like to argue that evolution can't be science because we can't directly observe evolution in action — and since science requires direct observation, evolution is necessarily excluded from the realm of science. This is a false definition of science, but more than that it's also a complete misrepresentation of how humans actually work...Inferential Evidence for Evolution - Evidence for Inferring EvolutionInferential evidence for evolution is evidence that does not involve direct observation of evolution but from which we can infer that evolution has occurred. The three main kinds of inferential evidence for common descent are contemporary homologies, biogeography, and the fossil record. Inferential evidence is open to interpretation, but this...Usefulness of Evolution - How is Evolution Useful?Theodosius Dobzhansky, one of the 20th century's most eminent evolutionary biologists, had it right when he said, 'Nothing in biology makes sense except in light of evolution.' Evolution is the conceptual paradigm that ties together all the life sciences. Without the explanatory framework provided by the theory of evolution, the biological...Observing Evolution - How Evolution Has Been ObservedThe most basic direct evidence of evolution is our direct observation of evolution occurring. This is also the most basic lie which creationists tell about evolution because they constantly claim that evolution has never been observed when, in fact, it's been observed both in the lab and the field repeatedly. Creationists count on this lie...Genetics & Mutations - How Genetic Mutations Drive EvolutionThe basic definition of evolution is a change in the gene pool of a population of organisms over time. All of evolution is based on genetic change. Scientists still have a lot to learn about the workings of genetic code, but science has built up a large volume of knowledge about how the genetic material of living organisms works. We have a pretty good understanding of what DNA does in general and, equally important to evolution, how DNA changes.Homologies & Evolution - Homologies as Inferential Evidence f…Homology has a specific meaning in evolution, but I will not be using that to avoid circular reasoning — we can't "prove" evolution using terms that assume evolution. I will use a more general meaning for homology: similarities between species that are not functionally necessary. In pre-evolutionary terms, the alternative type of similarity...Fossils & Evolution - Fossil Evidence Supports EvolutionWhen you hear talk of evidence for evolution, the first thing that frequently comes to mind for most people are fossils. The fossil record has one important, unique characteristic: it is our only actual glimpse into the past where common descent is proposed to have taken place. As such it provides invaluable evidence for common descent. The...

What is Evolution? Evolution Defined and ExplainedEvolution can be a difficult concept for people to come to terms with, especially if they do not have much experience with life sciences. Is evolution a fact or a theory? Does evolution explain the origin of life or not? These are important questions which people need to be able to understand and answer. Evolution is not a minor matter - it is, in fact, the cornerstone of all modern biology.

Evidence for Evolution - Is There Evidence for Evolution?In debates over evolution and creationism, it is common for creationists' to demand for "proof" of evolution (common descent). Science doesn't deal in absolute proofs, though. Scientific theories are provisional and are supported by evidence or data. Proof in science is not the same as proof in mathematics; in science, proof is gradually...Direct Evidence for Evolution - Evidence for Evolutionary TheoryThe direct evidence for common descent and evolution are enabling evidences. They demonstrate that common descent is possible and maybe even likely. However, they don't conclusively show that common descent occurred because no one was actually there to observe it over such a long period of time (the same problem that exists when …

The nature of the earliest forms of life on our planet are unknown and may remain that way, but we keep coming closer to understanding what they may have been like. Whatever they were like, it seems clear that they arose out of a process of molecular self-assembly. This process is commonplace in our universe. If you look up into the night sky, you’ll see countless stars and galaxies which arose spontaneously by a process of self-assembly.

Out of the featureless initial state of the universe they developed into the wondrous complexity we find today. There is no “vital force,” no galaxy-power which make them what they are — why imagine that such a thing is responsible for us? In 1953, Harold Urey and Stanley Miller set up an experiment to reproduce early chemical conditions of the Earth and added “lightning” to jump-start the process of forming amino acids, the building blocks of life. They achieved some success, but there were problems. The strongest objections, perhaps, is that amino acids aren’t all that difficult to produce — so what they achieved is perhaps not so remarkable.

Creationists like to argue that life couldn't have naturally developed from non-life because of entropy. Essentially, they claim that order and complexity, the reduction of entropy, cannot occur naturally — but this argument simply doesn’t work.

First, the Second Law of Thermodynamics, which limits the ability of a natural system to have a decrease of entropy, only applies to closed systems. When a system is open and can exchange energy with the outside, then that open system can have a decrease in entropy and an increase in order. The most obvious example of this is, coincidentally, a living organism. All organisms run the risk of approaching maximum entropy, or death. But they manage to avoid this by drawing in energy from the world: eating, drinking, and assimilating.

Second, whenever a system experiences a decrease in entropy, a wider price must be paid. When a biological organism absorbs energy and grows — thus increasing in complexity — work is done. When work is done, it is not done with 100% efficiency. Some energy is always wasted and some given off as heat — this means that in the larger context, overall entropy is increased even as entropy decreases locally within an organism. Thus, the Second Law is not violated.

We can see how organization can arise out of entropy by looking at the example of gas clouds — and the key to it all is gravity. If we examine a small amount of gas in an enclosed space and at uniform temperature, we find that it does absolutely nothing. The system is at its state of maximum entropy and we’d have no reason to expect anything to happen.

But if the mass of the gas cloud is large enough, then gravity will begin to play a significant role. Over time, pockets will start to contract, exerting even higher gravitational forces on the rest of the mass. The clumping centers will contract further, beginning to heat up and give off radiation, thus allowing for temperature gradients to form and heat convection to take place.

Thus, a system which was supposed to exist in thermodynamic equilibrium and maximum entropy has moved on its own to a system with less entropy, but more organization and activity. Clearly, gravity changes the “rules” of a system in important ways, allowing for events which might seem to be excluded by thermodynamics.

The problem is that appearances can deceive, and the system described above must not have been in true thermodynamic equilibrium. Although a uniform gas cloud should stay as it is, it still seems to “go the wrong way” in terms of organization and complexity. Life works the same way, appearing to “go the wrong way” with complexity increasing and entropy decreasing. In reality, though, it’s all part of a very long and complicated process whereby entropy is eventually increased, even if it appears to decrease locally for (relatively) brief periods.

During a brief skirmish I had the other day on Twitter with young-Earth creationist Joe Cienkowski (of self-published anti-atheist tract fame), he asserted that the theory of abiogenesis is the same as the now-disproven hypothesis of spontaneous generation. This is, of course, as with pretty well every other assertion about science ever made by Joe, patently false.

Spontaneous generation held that life in its present form today could form from non-life, and did so all the time — for instance, aphids sprang from dew on plants, maggots emerged from rotting meat, and mice were created from wet hay. In 1859, Louis Pasteur performed experiments that put the final nail in the coffin of the hypothesis. He proved definitively that life does not spring, fully formed and unbidden, from any recipe of inorganic or dead organic matter. So the question of the origin of life was reopened for the first time in centuries.

Abiogenesis, on the other hand, does not predict that life in any form known today — not even the simplest single-celled life forms — were created in some flash of magic or through some arcane recipe of components. That would be creation, in the sense of a personal creator deity. Rather, it predicts that, as life is made up of chemical reactions, and the constituent components of life can self-arrange given certain conditions, there is some point in Earth’s early history wherein a chemical chain reaction went runaway and breached the fuzzy barrier between chemistry and biology. All biology is is one single long, unbroken chemical reaction that can be traced back to whatever initial condition sparked it billions of years ago.