Yoga derives from prehistoric roots, and develops out of Ancient Indian asceticism (tapas). Yoga as a Hindu philosophy ("darshana") is first expounded in the Yoga Sutras of Patanjali. This earliest school of Yoga retrospectively came to be known by the retronym Raja Yoga to distinguish it from later schools.
Indus Valley civilization (ca. 3300–1700 BC)
Several steatite seals discovered at Indus Valley Civilization (c. 3300–1700 BC) sites depict figures in a yoga- or meditation-like posture, "a form of ritual discipline, suggesting a precursor of yoga", according to Indus archeologist Gregory Possehl. He points out sixteen specific "yogi glyptics" in the corpus of Mature Harappan artifacts that suggest Harappan devotion to "ritual discipline and concentration", and that the yoga pose "may have been used by deities and humans alike." Some type of connection between the Indus Valley seals and later yoga and meditation practices is supported by many other scholars.
Karel Werner writes that "Archeological discoveries allow us therefore to speculate with some justification that a wide range of Yoga activities was already known to the people of pre-Aryan India." A seal recently (2008) uncovered in the Cholistan desert was described by Dr. Farzand Masih, Punjab University Archaeology Department Chairman, as depicting a "yogi". Thomas McEvilley writes that "The six mysterious Indus Valley seal images...all without exception show figures in a position known in hatha yoga as mulabhandasana or possibly the closely related utkatasana or baddha konasana...."
The most widely known of these images was named the "Pashupati seal" by its discoverer, John Marshall, who believed that it represented a "proto-Shiva" figure. Many modern authorities discount the idea that this "Pashupati" (Lord of Animals, Sanskrit paśupati) represents a Shiva or Rudra figure. Gavin Flood characterizes the Shiva or Rudra view as "speculative", and goes on to say that it is not clear from the 'Pashupati' seal that the figure is seated in a yoga posture, or that the shape is intended to represent a human figure.
Upanishadic (ca. 800-100 BC)
While the most ancient mystic practices are vaguely hinted at in the Vedas, the ascetic practices (tapas) are referenced in the Brāhmaṇas (900 BCE and 500 BCE), early commentaries on the Vedas.
In the Upanishads, an early reference to meditation is made in Brihadaranyaka Upanishad, one of the earliest Upanishads (approx. 900 BCE). The main textual sources for the evolving concept of Yoga are the middle Upanishads, (ca. 400 BCE), the Mahabharata (5th c. BCE) including the Bhagavad Gita (ca. 200 BCE), and the Yoga Sutras of Patanjali (200 BCE-300 CE).
In the Maitrayaniya Upanishad (ca. 200-300 BCE) yoga surfaces as:
Shadanga-Yoga - The uniting discipline of the six limbs (shad-anga), as expounded in the Maitrayaniya-Upanishad: (1) breath control (pranayama), (2) sensory inhibition (pratyahara), (3) meditation (dhyana), (4) concentration (dharana), (5) examination (tarka), and (6) ecstasy (samadhi).
An early reference to meditation is made in Brihadaranyaka Upanishad, the earliest Upanishad (approx. 900 BCE). Yoga is discussed quite frequently in the Upanishads, many of which predate Patanjali's Sutras. The actual term "yoga" first occurs in the Katha Upanishad. A Rig Vedic cosmogonic myth declares an ascetic with "folded legs, soles turned upwards" as per his name.
Modern growth of yoga in the West
Currently, it is estimated that there are about 30 million people in America, and 1 million people in the United Kingdom practicing hatha yoga.
Yoga (in the West) is an exercise-related and posture-related technique that involves gentle stretching, breath control and meditation... various different forms of yoga, including Hatha (most common in the UK), Ashtanga and Iyengar exist. Yoga has been combined with various other exercise techniques to produce “fusion” classes, for example Yogalates, Body Balancing and Body Conditioning.
Bikram Choudury was sued in U.S. Federal Court by a collective of yoga studios that challenged his interpretation of copyright law. The lawsuit resulted in a confidential settlement agreement.
There have been many attempts to introduce regulatory standards, and various teacher training certification schemes exist.
Consumers face extensive and sometimes, conflicting information about what Yoga really is and what credentials, (if any) they should seek in a Yoga instructor.
In the UK, marketers wanting to make claims about improving strength, endurance, co-ordination or flexibility should hold "robust evidence".