One evening, one of my friends asked me a question: "Why do they put black olives on Mexican pizza? Do olives even grow in Mexico?". As I pondered this issue, the idea came to me to start a blog about questions like this. Surely, we can't be the only people to have wondered about this. Even if we are the only people to ask questions like these, well, at least I can have some fun by starting a blog that answers these questions.
Checking into the second part of the question, I discovered that olives indeed grow in Mexico. The Mexican government started planting them about 50 years ago (http://www.newton.dep.anl.gov/askasci/bio99/bio99581.htm). Olives are not native to Mexico, however. They were brought from Spain to Peru, and in the 1700's, they were introduced to Mexico by Franciscan monks (http://www.news.ucdavis.edu/search/news_detail.lasso?id=8487).
Exactly why black olives are used on Mexican pizza is the other part of the question. My theory is that when olives were introduced to Mexico, they were absorbed into the local cuisine. When someone came up with the idea for a "Mexican pizza", they naturally incorporated the black olive into their creation. However, that's my theory, not a fact. Perhaps you have information about this? Please send your theories, comments and information on the subject to firstname.lastname@example.org.