But what are the odds of Luke and Leia turning out to be Force sensitive?
In mating, it's a crapshoot which of your two alleles you'll pass on to your children - the odds are 50-50, and it becomes a game of probability. The coupling of someone with two recessive alleles (ff) and a dominant and recessive allele (Ff) has four possible outcomes that can be easily mapped out in something called a Punnett square diagram, like the one to the right. As you can see, the children of this pairing will either have one dominant and one recessive allele, or two recessive alleles, and there's an equal chance of either outcome: 50 percent.
If Luke and Leia were identical twins, then they would have the same DNA, which would explain why both would be Force sensitive. Unfortunately, they are fraternal twins - else they would be Luke and Leo - so Luke being Force sensitive has no bearing on Leia. What are the odds, then, of having two children turn out to be Force sensitive? 25 percent - that's just basic probability, not genetics. If you flip a coin twice, there are four possible outcomes: a head and a tail, a head and a head, a tail and a head, and a tail and a tail.
So the odds weren't in favor of both Luke and Leia turning out to be Force sensitive, but they aren't incredible odds, either. But what about the odds of Force users being born into the population at large? Well, there are six different potential parental couplings:
- FF with FF
- FF with Ff
- FF with ff
- Ff with Ff
- Ff with ff
- ff with ff
That last case - a Force user with another Force user - will always produce offspring who are Force users, since they only have recessive alleles to pass down. The first three cases will never result in Force users, since one parent only has dominant alleles to pass down. The fifth case is the Vader example we previously discussed, which results in a 50 percent chance to produce a Force user, while the fourth case is one in which you have two non-Force users who are carriers of the recessive Force sensitivity allele. In that case, the odds of these non-Force users having a potential Jedi baby are 25 percent, as demonstrated in the follow graphic.