The second source of variation is recombination. This involves shuffling the genes and is the reason that children resemble very closely their parents but are not exactly like either one. The discovery of the principles of recombination was Gregor Mendel's great contribution to the science of genetics. Mendel studied seven pairs of traits in the garden pea. In each of these he showed that while traits might be hidden for a generation they were never lost, and when new traits appeared it was because their genetic factors had been there all along.
Recombination makes it possible for there to be limited variation within the created kinds.
But it is limited because virtually all of the variations are produced by a reshuffling of the genes that are already there. A few examples might help us appreciate the limited nature of variation through recombination. Many varieties of chickens have been produced from the wild jungle fowl, a lot of variation. But no new varieties are being produced, because all of the genes in the wild jungle fowl have been sorted out into the existing varieties, limited variation. From the science of plant breeding we have the example of the sugar beet.