Aggañña Sutta

The Agganna Sutta explains this evolution in terms of a mythical story. On one occation a young Brahman,named Vasettha, joined the Buddhist Order and thereby became a monk of equal status with men from lower castes, for this he was severely reprimanded by other Brahmans. They said he had forsaken a divine and holy order; that the Brahmans were a special race born from the mouth of God. To repudiate these contentions the Buddha explained to Vasettha the true origins of humanity and said that all people had a common ancestry.

The first beings are described as sexless, vaguely shaped creatures whose bodies lacked solidity in the beginning, they fed on a savoury earth which first appeared as a scum on the ocean surface. This continued for a great length of time during which their bodies increased in solidity and diversity began to appear in their shapes. With the disappearance of the savoury earth, growths similar to mushrooms appeared in the soil and the earth's inhabitants fed upon these. After these vanished, creeping plants became the source of nourishment and finally rice. All this is said to have required great periods of time and eventually sexual characteristics developed. Following this, the words "man" and "woman" and later "people" make their first appeareance in the sutta with regards to the creatures under discussion. (from here)

This is a brief summary of the scripture read more here and PDF version here

While the story of the world's beginning is considered a myth, on the other hand, the buddhist doctrine requires a constant sceptical approach, where one must see and prove it before one believes it (ehipassiko). However, the profound insight of the Buddha in two major fields: science (cosmology) and social structure's origin indeed was revolutionary in his era.

On the science part, Buddha implied the theory of the Evolution of Universe, where it is said to shrink and then expand in repeated cycles.

While on the social science part, the Buddha's words implied the equality of origin in the human race, whether by their sex, appearance, or by other categories which were founded later based on physiological differences. Buddha also emphasized that the social structure is formed voluntarily, based on righteousness and necessity, not based on Divine Forces as some theories stated.

The Monarchy is also formed voluntarily, and the people elect the most righteous and capable person, which implied the Democracy concept. The Monarch accepts a 'share of rice' as his reward to rectify the social order, which is the origin of voluntary reward which evolves into the taxation concept. However, the Buddha states that the Monarch is regarded worthy not because of his divine right but due to his righteousness in deeds. [2]

The Buddha's message was clear, however, that the best thing in the world is Truth (Dhamma) and everything is created, measured, and valued based on Truth and not from something other.