Not the first time this has been asked.

Tl;dr: we don't know, and it's never been mentioned. The statues themselves are a mystery.

While it's commonly assumed the Mhachi were mostly Lalafell since Belah'dia (and through them Sil'dih and Ul'dah) is descendant from Mhach, we have no indication this was the case and until we're told otherwise we can only assume Mhach was about as cosmopolitan as the rest of Eorzea.