But I don't think that much can be chalked up to Elezen having longer lifespans. They aren't Lord of the Rings elves, and don't live for centuries on end, so the comparative difference in lifespan between them and Hyur isn't so huge. If anything, it's probably only a few decades at most, and for that matter something that is probably only the case with Wildwoods- most Duskwights don't share their living conditions, and likely have a higher rate of dying at around the same age as everyone else.
If you can't find lore sources on anything official, you might be basing your assumption on fanon rather than canon. Seems like that's a running issue around here lately.
Here's the thing about "intelligence". The way you're talking about it, you seem to be thinking about availability of knowledge by way of study or research, rather than an inherent mental quality. And that's not something intrinsic to anybody based on race. It's something that comes from one's circumstances, the availability of material to learn from, etc. And for centuries, Eorzean culture has been a melting pot of influences from all five of the major non-beastman, non-Garlean races. They developed concurrently, share a history, and share resources like research and knowledge. So the comparative intelligence of any individual in Eorzea is more to do with their access to higher learning, rather than their brain being naturally better at knowledge. Midlanders aren't all going to be super-geniuses as a flavor thing- you may note that there are numerous Midlander NPCs in the game, none of which who are portrayed as more intelligent than anybody else. Hell, look at the figures of authority in the most "intellectual" guilds and professions: the Thaumaturges' Guild is run by a group of Dunesfolk Lalafell, the Arcanist guildmaster is a Seeker of the Sun Miqo'te and his deputy is a Sea Wolf Roegadyn. The Scholar questline involves a fairly intellectual Plainsfolk Lalafell (and another Lalafell scholar in the backstory). Even in the Scions of the Seventh Dawn, the members of the organization that are shown to be more focused on learning and intellectual subjects are not the Midlanders. We've got a couple of wise and mysterious Elezen, and of course Papalymo, who is a Plainsfolk! I don't think anybody, looking at Thancred and Minfilia, would go "ah, yes, the stereotype for Midlander Hyur like these two is that they're SUPER-GENIUSES".
If you can't find lore sources on anything official, you might be basing your assumption on fanon rather than canon. Seems like that's a running issue around here lately.
Here's the thing about "intelligence". The way you're talking about it, you seem to be thinking about availability of knowledge by way of study or research, rather than an inherent mental quality. And that's not something intrinsic to anybody based on race. It's something that comes from one's circumstances, the availability of material to learn from, etc. And for centuries, Eorzean culture has been a melting pot of influences from all five of the major non-beastman, non-Garlean races. They developed concurrently, share a history, and share resources like research and knowledge. So the comparative intelligence of any individual in Eorzea is more to do with their access to higher learning, rather than their brain being naturally better at knowledge. Midlanders aren't all going to be super-geniuses as a flavor thing- you may note that there are numerous Midlander NPCs in the game, none of which who are portrayed as more intelligent than anybody else. Hell, look at the figures of authority in the most "intellectual" guilds and professions: the Thaumaturges' Guild is run by a group of Dunesfolk Lalafell, the Arcanist guildmaster is a Seeker of the Sun Miqo'te and his deputy is a Sea Wolf Roegadyn. The Scholar questline involves a fairly intellectual Plainsfolk Lalafell (and another Lalafell scholar in the backstory). Even in the Scions of the Seventh Dawn, the members of the organization that are shown to be more focused on learning and intellectual subjects are not the Midlanders. We've got a couple of wise and mysterious Elezen, and of course Papalymo, who is a Plainsfolk! I don't think anybody, looking at Thancred and Minfilia, would go "ah, yes, the stereotype for Midlander Hyur like these two is that they're SUPER-GENIUSES".