Math

Folks following this model of history can often find themselves making unexpected mathematical jumps. Like a reaction to this headline:

Indiana Jones? FBI finds thousands of artifacts in 91-year-old's home

The natural reaction for everyone, of course, is to say “Indiana Jones? He can’t be 91 - he’s Lost Generation, born late 19th century, the youngest of which anywhere is 113 years old by now. A 91-year-old was born in 1923 or 1924 - that’s GI Generation, and nearly at the end of it as well.”

For those who didn’t realize when Indiana Jones was born, there are a couple of ways to identify his birthdate, some rougher than others. The first movie gives a date of 1936. If Jones didn’t look like he was in his late 30s/early 40s, one could infer that from his holding a professorship. Either way, that has him born in the 1890s. (Or you could check Harrison Ford’s birthdate, see that the movie came out in 1981, and calculate from there - but folks get cast in movies for different reasons than being the correct age.) Mostly, though - like other 1930s serial heroes - Indiana Jones is a classic Reactive/Nomad: Living in interesting times, self-sufficient, pragmatic - and with morally questionable attributes, as noted by both Marion and Belloq.

For those who didn’t realize it MATTERED when he was born...well, yes, it’s fundamental to the model. The primary concept is that people alive during a particular time are all affected by events during that time, and the specific effects are dependent on what stage of life they are in. Young adults - who can take direct action with regards to a Crisis (for example) -  will react differently than children, who are subject to the actions of others.  The different generations can be completely reduced to people born during specific timespans. 

Whether all people in a generation really match the archetypes is a different question.  It works for him, though: With a (clearly Missionary Generation) father focused - quite literally - on the Holy Grail, Indiana rebels via an archeological career that does not require a spiritual component. We see him with ancient pagan idols, neolithic tombs, Egyptian hieroglyphics, but neither the Ark nor any of the other relics he later pursues are artifacts of his religion - if any. He is only trying to save the world.