We may need a close connection to that way of life again and not have to relearn it from scratch.
This strikes me more as one of those things that is shocking to hear but not incorrect. People get more upset that someone said it without actually having a counterargument.
He's not saying that we _should_ live that way but that we might need to.
But in no way is "their knowledge" (which I think is an overly generous use of that term) - acting in the role of a knowledge seed bank.
Not to mention all the time they spent in nature which is impossible now.