So I made a comment on today's TIL thread about the age of Leonidas, in which I say that ancient soldiers were often older than we think. I'm not a historian and I can trace my impression back only to a couple of faint recollections: (1) a TV documentary about Alexander the Great in which his veterans were described (if I remember well) as being tough old guys in their 50s and 60s, but I can't recall any more specifics, and (2) I also seem to recall reading something about the Roman 'Triarii' units largely consisting of men in their 40s and upwards, despite being one the most powerful units in the Roman army.
One of the comments asked me for sources but I can't recall the details of my original souces or find any on the internet. Is my comment correct or is it nonsense? Were soldiers in ancient times older than our modern idea of the 'normal' age of a soldier?
You mention Triarii; these were, by the time of the Middle Republic, the veterans of the legion, but they were not going to be used in every battle. In addition, it's not clear how old exactly they were. Old men in their 40s wouldn't be the most common we can assume, but certainly not out of the question. The Imperial period is a little easier. The average age at which one enrolled in the legions in Rome during the Imperial Period was often actually quite late it seems to our own assumptions; we might expect 15 and 16 year olds to enroll, but the Romans wanted men, and so recruits seem to have been around 20 when they enrolled. If you factor in a 20 to 25 year commitment, plus the possibility of some evocati (men who re-enrolled after being discharged), you are certainly going to have some older men. Now, I think we can definitely speculate on the 'average' as it were by making some educated guesses. First, let's assume that the base average is going to be halfway between retirement and enlistment, so 30. Then you have to factor in that a not insignificant number of men are going to be discharged every year for medical reasons (the same as in a modern military), so that will lower us down a notch. I think we can safely say that the average age of the soldiers then was likely somewhere between the ages of 25 and 30. Given that we do know that many men did retire from the legions after completing their service, that also means that many men are going to have been in their 30s and a not insignificant number in their 40s. The tricky part of all this is that in a legion, there were not really any non-combat positions. Every legionary was supposed to be able to fight and carry their equipment. However, some, like the engineers, were exempted from certain camp duties, and it seems likely that these men, given the value of their experience, might be older on average.