No one knows exactly how old yoga is. The oldest archeological evidence of yoga's existence are some stone carvings portraying figures in different yoga poses that were foind in the Indus Valley, on the border between Pakistan and India. The findings are estimated to come from around 3000 BC. Yoga was fist mentioned in the Vedas, a collection of writings from around 2500 BC.
Classical Yoga is based on five limbs-
Yama: Self-restraints Niyama: Inner Observances Asanas: Movements Pranayama: BReathing Exerices Pratyahara: Withdrawal of the senses Dharana: Concentration Dhyana: Meditation, and Samadhi