Speed. This is more of a physics question.
Somatic cells are diploid (2n) while gametes are haploid (n). In other words, gametes have half the number of chromosomes that somatic cells do.
Increase of earth's average temperature
If the theory was real, two parents with ear lobes attached could not have a child with a free earlobe. A offspring from A x A matings are marginally more, but the large numbers of F offspring from A x A matings and A offspring from F x F matings suggest that this is not a single-locus, two-allele trait.
