In this series, I will do my best to explain evolution in a way that everyone can understand. The first three posts will present the evidence for evolution, while the last post will answer commonly asked questions about evolution (Such as, "Can Evolution Increase the Information in the Genome?")
The First thing that anyone should understand about Evolution is Natural Selection. Berkeley University has set up a page that explains the process very neatly. I also attempted to explain it in a video I created. "How Stuff Works" Author Marshall Brain put it this way,
"As mutations occur, natural selection decides which mutations will live on and which ones will die out. If the mutation is harmful, the mutated organism has a much decreased chance of surviving and reproducing. If the mutation is beneficial, the mutated organism survives to reproduce, and the mutation gets passed on to its offspring. In this way, natural selection guides the evolutionary process to incorporate only the good mutations into the species, and expunge the bad mutations."
The Peppered Moth Story is great for understanding Natural Selection as Well. The Article I linked to defends the story against recent accusations that the story is a fraud or fabrication.
Evidence #1 Fossil Succession
(The Order of the Fossil Record)
Imagine that you were to go on a dig for fossils. Imagine the first thing you uncover is a small, horselike-creature with five toes. Suppose you began digging a little higher in the same rock, and you found a similar creature, except it had four toes. You then go higher still, and find a skeleton that looks very much like a horse, except it has three toes. What would think about this? To understand what I am saying, please look at the infamous horse series. Now, finding fossils which are, say part reptile and part bird, like Archaeopteryx, is a prediction of evolution. But this isn't in itself the best evidence for evolution, the evidence is the fact that we see progression. With every one of the sequences below, the higher up we go in the strata, the more that life looks like it does today.
The Origin of Whales and the Power of Independent Evidence
Early Vertebrate Evolution
Sea Sloth Evolution
Another Mammal-Reptile Fossil
Evolution of Mammals
Over 400 "Missing Links"
The Top Ten Missing Links
Evolution of Birds
National Geographic On Birds And Dinosaurs
Summary of Many Famous Examples
Online Booklet About Fossils
Why is the fossil record littered with sequences that just so happen to be in an order that makes them look like they evolved? I cannot make sense of it without evolution. In fact, I think anyone who saw these sequences would suggest evolution, had it not already been proposed so long ago.
Evidence #2 Embryology
Now, the first thing I want to make perfectly clear is that I am NOT referring to Haeckel’s work nor to his long discarded theory. Ontogeny does not recapitalate Phylogeny, but there are some interesting similarities in development which I believe are best explained by evolution.
Mammal Embryos develop three sets of kidneys. The first, pronephros, is the same set found in primitive fish like Lampreys. After 3.5 weeks, the mammal embryo replaces it. The second set, the mesonephros, is the same set found in higher fish and amphibians. In human males it gives rise to urogenital structures, while in females the remnants are vestigial. The third set (Metanephros) is the set which develops and becomes the adults set of kidneys, and it is the same set found in mammals and birds.
Snakes as well as Dolphins are known to develop legs as embryos, only to reabsorb them later.
Whales Develop hair as embryos, only to discard it later (except for the nosehair).
Why do they do this? Why go through these stages? Why not develop their adult forms more quickly? These facts are best interpreted as developmental remains of their past.