The Rig Veda is a sacred text within the Hindu tradition. It is also the oldest Vedic text dating before 1200-1000 BCE.
The Rig Veda is composed in archaic, highly stylized Sanskrit. It contains 1028 poems grouped into 10 “circles” (or books, also called mandalas), and includes verses of praise addressed to the Vedic gods (Agni, Mitra, Varuna, Indra, and Soma), to some early chieftains, as well as to natural phenomena such as the sky, earth, wind, waters, rain, and more.
The most important gods in the Rig Veda are Agni and Indra. Agni is present and visible on the offering ground, and he receives and transports offerings to the gods. Indra is the leader of the present generation of the gods and a major actor in the early stages of creation. Deified natural phenomena include Surya (“the male belonging to the sun”), Dyaus (“Heaven, Sky”), Vayu (“Wind”), and Parjanya (“Thunder”).
The hymns were composed by members of various clans of poets and were transmitted as “private property”. They were often “copyrighted” by including the names of the individual poets or clans. The poetry in the Rgveda is both deep and complex,
“[I]t is based on the poetical norms of the preceding Indo-Iranian and Indo-European periods, it refers to many fragmentarily known myths, uses many archaic formulas and set phrases, and a vocabulary that was already archaic then, and its expression in general is very elliptical. There also are stanzas that praise the local chieftains, who were sponsors of R.gvedic ritual” (1).
Some of the names attributed to the authors of Rig Vedic hymns seem to be partially correct although others are post-Rig Vedic and artificially derived from some keywords in the hymns. The Rig Veda contains mostly ritual contents but also hymns of a philosophical speculative nature. Some hymns, such as the love story of Urvashi and Purūravas, have been used by the later Epic and classical poets.
The Rig Veda contains the earliest reference to the caste system and serves as its basis. It speaks of the god Purusha whose body consists of the four varnas: Brahmins (priests) constitute its mouth, Kshatriyas (warriors and kings) its arms, Vaishyas (merchants) its thighs, and Shudras (laborers and servants) its feet.
References
1. Flood, Gavin. 2008. The Blackwell Companion to Hinduism. Hoboken: John Wiley & Sons. p. 71.
Bishop's Encyclopedia of Religion, Society and Philosophy 
Hi James:
Question: Sri Aurobindo interprets the 4 varnas in the most ancient Vedic tradition as primarily psycho-spiritual, not hereditary or “class” based in the modern sense.
Many academics consider this an apologetic approach. When I first heard of it in the mid 70s, after having read the academics, Sri Aurobindo’s interpretation was exactly what I had come to on my own while reading the academics.
I’d be interested to hear if you think there’s any validity to the possibility that the varnas were actually a developmental scheme, having much in common with Piaget, Kohlberg and others (admitting the developmentalists’ many limitations, scientifically as well as philosophically)
Thanks!