[Snake]

I agree, sorry but humans are not special or supposed to be, until we think of a reason why they exist.

I once thought: "Oh, but they use 42 aptitude, they gain 1 stat point to put somewh--" Nope, Hyattrs and Mechanations also have that. Especially Hyattrs, who have racials and a looot of benefits, including the possibility to become immune to fire damage.

Whatever 'healthy' benefit I could think for humans using SAN is that every 20 SAN they get +1 points added to their diminishing returns, as:

Imperials get the +1 (per 25 SAN) bonus on all stats.
Tannites get a +2 (per 25 SAN) bonus on STR/SKI.
Onigans get a +2 (per 25 SAN) bonus on CEL/LUC.
Chatarans get a +2 (per 25 SAN) bonus on DEF/VIT.
Lispoolians get a +2 (per 25 SAN) bonus on FAI/RES.
Karatens get a +2 (per 25 SAN) bonus on WIL/SAN.

I mean, they do have to survive their everyday problems (such as facing the deserts, dealing with every sorts of situation or studying magic), that must leave some impact in their bodies. The way it is, you can barely difference a human from another.