people started having sex a lot earlier a few hundred years ago (when people die at 30, they'd better)
Where did you get that from? Do you mean people started having sex before puberty?
As for "when people die at 30", that's a common misunderstanding of life expectancy at birth statistics. Life expectancy at birth of 40 (the most common figure quoted for Early Modern Europe) does not mean everyone dies at 40. It's an average, and the reason it's so low is infantile mortality. At birth, you had a fairly high chance of dying in the first week of life, (first year, first ten years). But if you got through to 30 you had a decent chance of reaching 60 or 70.
No, that wouldn't make much sense, would it? But certainly earlier than the current 17. IIRC the age of consent was considerable lower in the olden days, in spite of people hitting puberty later than they do today, because of worse nutrition. Peak oil is not an energy crisis. It is a liquid fuel crisis.
