My experience of learning Advanced Trigonometry and Calculus is that it was done to 17 and 18 year olds (School Curriculum in Australia). I assumed that it was similar in the UK, US and Europe.
In the book Master and Commander we see the main character Jack Albury tell of his childhood learning mathematics. It appears he learned Cotangents and Integration at age 12.
Now I'm not saying this is not possible, and that there are probably 12-year-olds out there with untapped potential. I'm trying to understand what Mathematics would have been taught at this point in time (to sailors for navigation). Is it likely that they learned a rote formula for navigation, and understanding the stresses on a ship, or would they have learned first-principles?
Now this novel is set in the period of English History [1800-1815] and is generally regarded to be meticulously researched historical fiction.
My question is: Has the age at which we teach Mathematics changed over the last two centuries?
Well It depends on what you think about mathematics. Generally, Through history we all learn mathematics from a very young age because We learn counting.
Now Isaac newton didn't learn calculus in University because he is the one who came up with calculus in the first place and therefore, Nowadays, The mathematical curriculum for university involves way more advanced mathematics compared to 100 years back. Now we have graph theory , combinatorics , Modern Algebra , Number theory and topology. This is way more math than they did 100 years ago, I would say even Einstein didn't do a lot of math compared to People doing research now.
In the future, I think people will learn more about modular arithmetic and number theory earlier than they do nowadays.