In the Sutta Nipata, translated by Fausboll in Sacred Books of the Past, (Vol.X pp 111–13), there ensues a controversy between two disciples of Brahmanic origin, arguing about caste and what makes one person superior to another person.

Being unable to convince one another, they approach the Buddha and request his help in resolving the quandary. The first disputant, Bharadvaja, argues that a Brahmin is superior based on birth alone, while the second disputant, Vasettha, asserts that a person becomes a Brahmin based upon meritorious actions only.

For the sake of clarity, as the wording of Fausboll’s translation is antiquated, I have paraphrased and condensed the words of the Buddha's response:

The Enlightened One claims that he can delineate the exact distinction between living beings, following the differences in diverse species:

With grass and trees, there are distinctions which designate species, and these species are many, although they may not always be apparent. With worms and moths, and different sorts of ants, there are distinctions which designate species, and their species are many. With four-footed animals, small and great, there are distinctions which designate species, and their species are many. With the serpents, the long-backed snakes, there are distinctions which designate species, and their species are many. With fish which range in the water, there are distinctions which designate species, and their species are many. With the birds which are borne along on wings and move through the air, there are distinctions which designate species, and their species are many.

According to the Buddha, unlike with grasses, trees, worms, moths, fish, beasts, birds, and so on, among men, there are no distinguishing characteristics of species. There are significant distinctions regarding other beings endowed with bodies, but in the case of humans any differences are merely nominal.

Where humans are concerned, there are no significant distinctions that would warrant designating separate species, neither regarding hair, heads, ears, eyes, mouths, noses, lips, nor brows; nor as regards their necks, shoulders, bellies, backs, hips, breasts, female organs nor sexual intercourse; nor as regards their hands, feet, palms, nails, calves, thighs, color, nor voice. There are no distinctions that would constitute separate species. Occupations such as cow herder, farmer, archer, or soldier do not make men Brahmins. Neither do rank nor status. Nor can a person be deemed a Brahmin based on birth by a particular mother.

According to the Buddha, unlike in the case of grasses, trees, worms, moths, fish, beasts, birds, and so on, among humans there are no distinguishing characteristics of species, because apparent differences between humans are not based on inviolable biological factors but rather on worldly conventions and classifications (savanna). Any distinctions made based on differences in skin color (Pali: vanna), hair form (kesa), the shape of the head (sìsa) or the shape of the nose (nása), and so on, are only worldly conventions and would not justify categorizing humans into differing species.

When the Buddha teaches treating all people equally, as fathers, mothers, brothers, and sisters and family, irrespective of race or caste, there seems to be some sense of ultimate veracity in this assertion, something higher than mere village convention.

Brahmins claimed that their hereditary characteristics included being handsome (obhirupo), fair (dassaniyo), endowed with an excellent complexion (paramaya vanna-pokkharataya samannagato), and of the fairest color (brahma-vanni), by virtue of which they claimed superiority over those of a dark complexion (D. I. 114), but a little empirical research quickly proves this not to be true.

The terms “Aryan” (ariya) and “non-Aryan” (anariya) frequently appear in Buddhist texts, but they are never used in a racial or caste sense. The racial sense of superiority associated with “Aryan” is based on social inequality; whereas, in the Buddhist sense, Aryan' connotes a moral, spiritual sense of purity, leading to moral superiority and detachment, free of any association with race or birth.