A random process of DNA exchange that occurs during sexually reproduction (meiosis), and which gives rise to chromosomes containing genes not found in the cells of either parent. This genetic rearrangement can be a considerable source of variation for natural selection to acts upon. Consider, for example, that there are 2²³ possible new combinations of chromosomes during human fertilization, given that we inherit 23 chromosomes from our mother and other 23 from the father. Just these combinations alone are greater than the number of people who have ever lived on the earth.
See Biological evolution, Chromosome, Copying errors, Darwinism, Diploid, DNA, Evolutionary theory, Genetic drift (or random walk), Haploid, Meiosis (or reduction division), Mosaicism, Mutation (biology), Theory of natural selection