- Variation exists in all populations.
- Some of that variation is heritable.
- Some of that heritable variation has an influence on survival and mate attraction.
- Characteristics that increase the number of mating opportunities become more common each generation, while those that interfere with mating opportunities become less common.
- DNA is a self-replicating molecule.
- Crossing over during mitosis and meiosis alters the sequence of base pairs on a chromosome, which results in combinations of genes that had not previously existed.
- Copying errors (mutations) can also arise, because the self-replication process is of high, but not perfect fidelity. Those mutations also increase the range of combinations of alleles in a gene pool.
- Sampling errors can occur in populations that alter the frequency of the various alleles for reasons other than survival/reproduction advantages.
- Migration of individuals from one population to another can lead to changes in the relative frequencies of alleles in the recipient population.
- Populations of a single species that live in different locations are exposed to different environmental conditions that can favor different traits. These environmental differences will cause two populations to accumulate different suites of characteristics.
That's what evolution is. If you have a problem with evolution, you have a problem with one or more of those points. Which one?
- There is no one simple evolution story explains briefly why the iconic ape-into-man image is wrong and also links to a large, detailed poster showing the evolutionary tree of land animals.