shiva lived in the cemetery with a skull for a begging bowl. like an aghora who still follow in his footsteps on the sadahana in varnasi the eternal city of shiva ! it started during the stone ages at the end of the Pleistocene around 10,000 BC. Practice makes perfect. When you repeat the same techniques over time your genes record this . At the quantum level of the DNA you can alter probability distributions of the quantum fields and modify your epigenome. Discipline and shradda makes humans close to perfect like the mother adi shakti. Tantra is science. learn by experience !