- Force talent seems to run in families.
- In fact, every child of a Jedi that we've seen - in the movies, and in at least most of the EU, for that matter - is force sensitive to a degree.
- Jedi aren't allowed to marry. They are a celibate order. (See #2 for why we don't have more evidence from the movies on whether or not force sensitivity runs in families.)
- For the past thousand years prior to the prequels, the Jedi order has been dying out slowly.
Darwin 1, Jedi Order 0.