Ohh it’s much worse than that. Usually humans would live to around 60 if they survived infancy before that. Their diet was varied and since food was a limited resource, there was no way of population blasts. But agriculture just fucked it all up. We stopped moving around since the land needed constant maintainence and since the diet became mostly carbohydrates, combined with back breaking work, our life expectancy dropped to 40. We didn’t domesticate wheat, wheat domesticated us. It took modern medicine… ie 20th century to get the average life expectancy up again.

I recommend you read the book called Sapiens. It’s an eye opener.