Sex and genetic shuffling
Sex can introduce new gene combinations into a population and is an
important source of genetic variation.
You probably know from experience that siblings are not genetically
identical to their parents or to each other (except, of course, for
identical twins). That's because when organisms reproduce sexually,
some genetic "shuffling" occurs, bringing together new combinations
of genes. For example, you might have bushy eyebrows and a big nose since your
mom had genes associated with bushy eyebrows and your dad had genes
associated with a big nose. These combinations can be good, bad, or
neutral. If your spouse is wild about the bushy eyebrows/big nose combination,
you were lucky and hit on a winning combination!
This shuffling is important for evolution because it can introduce new combinations of genes
every generation. However, it can also break up "good" combinations