Yoga’s history has many places of obscurity and uncertainty due to its oral transmission of sacred texts and the secretive nature of its teachings. The early writings on yoga were transcribed on fragile palm leaves that were easily damaged, destroyed or lost. The development of yoga can be traced back to over 5,000 years ago, but some researchers think that yoga may be up to 10,000 years old old. Yoga’s long rich history can be divided into four main periods of innovation, practice and development. It began in the Indus-Saraswati civilisation more than 5,000 years ago. The Rig Veda is the first text that mentions the word yoga. It was later streamlined and developed by Brahmin priests and sages and documented in the Upanishads which contain over 200 scriptures. The Upanishads derived the idea of ritual sacrifice and modified it, teaching the sacrifice of the ego through self-knowledge, action (karma yoga) and wisdom (jnana yoga). The Bhagvad Gita, composed around 500 BC, is replete with details about yoga. There are various schools of yoga that are followed. The Yoga Sutras Of Patanjali — written by Patanjali — which became hugely popular in the West, were written in the first half of the first millennium. Hatha yoga, another popular yoga form, came around the 11th century and has its origins in Tantra. The Hatha yoga (which focuses on breathing and calming down the mind), the Vinyasa yoga (which is faster paced and more fitness oriented), the Bikram yoga (founded by Bikram Choudhury, it is a form of hot yoga which is done in a hot environment to mimic the climate of India), the Ashtanga yoga (based on six series’ of poses that increase in difficulty, allowing you to work at your own pace) are extremely popular among yoga enthusiasts. Iyengar yoga, developed by BKS Iyengar, the Kundalini yoga — which is mentally and physically challenging — and the Jivamukti yoga (which is a Vinyasa style of yoga) are also popular.