This is an interesting part of Tolkien’s mythology because it was drawn from Greek myth instead of something more local to ingerland. Ancient Greek historians were in agreement that in the before times humans were taller, stronger, lived longer, and were overall more pure. In fact, most believed that if you could somehow follow your bloodline back in time, you would find that your ancestors got progressively more powerful and closer to immortal until you finally reached Gaia and Uranus at the beginning of all things.

Aragorn was the last of the Numenorians, who tended to live for hundreds of years, and he was specifically descended from Isildur. However, he was not nearly as long-lived as the originator of his line: Elros, half-elf son of Eärendil and Elwing the White, and twin brother of Elrond. Unlike his brother, Elros chose to live as a man for the remaining five centuries of his life, which was so long that when he died his son was already very old and had to surrender the scepter to his own son. Elrond and Elros were especially significant because their parents descended from the only two lines of half-elves: Elwing the White descended from the first half-elven union between Beren and Lúthien (who in turn was descended from the Elf Thingol and the Ainu Melian), whereas Eärandil was the son of Huor son of Tuor and Idril Celebrinal, princess of Gondolin (which would one day pass into the hands of men and become Gondor). In short, Aragorn descended not only from Elven heroes (one of whom killed Sauron’s master) but also the goddess who drew the borders of the land that Legolas was from. He’s not just a special boy, he’s a very, very special boy.

I’m only scratching the surface of how special the Numenorian line is here. However, Aragon, being the last of a long line of special boys, is much diminished compared to his ancestors. I would only expect him to live 250 years at most, and the rest of his cool abilities comes from being raised by Elrond himself.