I was taught that the sailors around the 1700's were chosen based on height, as they needed the room on ships. We were told that is why they were pretty much midgets compared to the locals, and why everyone (where Im from) is so much shorter today. Is this true?
This sounds like a pretty classic urban legend, and I'd be fairly skeptical of it. Caveat lector, I am not a historian of the Spanish navy, but as far as I know Spain (like most powers) had terrible manning problems for its fleet throughout most of the 18th and 19th century. They weren't really in a position to pick and choose potential sailors based on height.
Do you have a particular source for where you've heard that, or is it more of an "around town" sort of thing?