According to Doctrine, the Voth were the first species to evolve in their part of the galaxy and saurian species such as themselves were superior. Mammalian species such as Humans were looked down upon as a result.
Voth Doctrine dictated that because the Voth were the first to evolve in their part of the galaxy, they had the right to rule it. Thus, the notion that Voth evolved elsewhere, as proposed in the Distant Origin Theory, was considered heresy. (VOY: "Distant Origin")