What is known about enlightenment before the lifetime of the Buddha? Are there any claims that he was the first?

I am a non-Buddhist who is curious about Buddhism. In modern times, [Eckhart Tolle](https://en.wikipedia.org/wiki/Eckhart_Tolle) reports spontaneous awakening as a result of a sudden realisation that came out of intense suffering. As far as I am aware he was uninfluenced by Buddhism and underwent none of its training or techniques. I understand that the Buddha sat under a tree "until he was enlightened". This suggests to me that he knew of the phenomenon beforehand. Are there any claims that he was the first to achieve this state? What, if anything, do we know historically of the phenomenon of enlightenment before the life of Buddha?