Estimates of how long yoga has existed go back as long as 7,000 years or more, depending on how you interpret the data*. The theory and practice of yoga has evolved many times over throughout that long history, influenced by the religions and philosophies of its time, being refined and changed by its practitioners to fit their needs and bring them further along their journeys.
At this point you can more or less divide the practice of yoga into two categories: Classical Yoga and Tantric Yoga. The majority of us spend our time practicing Tantric Yoga these days, and no, it doesn’t involve any of the scandalous things you are thinking about. Well, okay, it kind of does, but that’s a longer story.
Classical Yoga was all about getting your spirit out of your body as quickly as possible. The story goes that Consciousness got trapped in this reality by mistake, and it’s a big problem. Therefore, everything about this life is problematic, including our bodies, thoughts, sense of self, and the multiplicity that surrounds us. Classical Yoga uses meditation techniques (among other practices) described in the Yoga Sutras to get in touch with the true Consciousness and liberate oneself from this reality. There were no asanas (yoga poses) except one: find a firm, steady seat for your meditation. Enlightenment is the goal, and enlightenment can only be found by leaving this reality and life.
Tantric Yoga arose in reaction to Classical Yoga. It said that this world is not a problem, and that if our consciousness exists in this world, then it must be a function of the same Source and we should celebrate it. Tantric Yoga affirms life and this reality, and seeks to honour the Source in everything.
Eventually asanas developed as a part of Tantric Yoga, in order to prepare the body and mind for meditation, to create a strong physical container for our energies, and to honour our bodies, as they were no longer crippling vehicles to be ditched as quickly as possible, but a part of our connection to the Source. Enlightenment is still the goal, but now enlightenment can be reached while in this reality.
This is hatha yoga (the name for any physical practice of yoga as well as a particular style of physical yoga). Interestingly, this practice that has become so popular it almost completely overshadows all other forms of yoga, is actually the youngest. Depending on how you qualify it, hatha yoga has only existed for a few hundred years!
Before, after, and in between the creation of Classical and Tantric Yoga, there have been many incarnations of yoga, and they keep changing. Recent innovations in hatha yoga include variations like yin, or entire schools of yoga like Anusara, and they keep growing.
This means that no matter what your reason for practicing yoga, and no matter what the particularities of how you prefer to practice, it’s all good! Yoga has been molded by each guru, teacher, and practitioner, and it will continue to change and evolve over time, so follow your heart and where it leads you in your yoga practice.
Of course, this doesn’t mean that you can just fly in all willy-nilly and do whatever you want, calling it yoga. Just as a true artist, one who revolutionizes the practice, innovates, and touches the hearts of the world, masters the teachings of those who came before them, so a yogi will explore and examine the paths of those who came before them before forging their own path.
*Fun fact about historical research: a lot of it is guesswork based on things like pictures painted on urns or plates. I first started exploring this in theatre history when I learned that what we know about early Greek theatre is pieced together from things like pictures of masks painted on broken urns. When it comes to yoga, there’s an old picture of a man who may be Shiva sitting in what could be lotus position. Could be he was doing yoga, could be he was employing one of the few ways to sit on the floor. Take your pick!