Most adults aren't mature enough and don't appreciate the risks they are taking. If they did, Jerry Springer wouldn't have stayed on the air these last 20 years. I don't think I've ever met anyone who wished they had waited longer to lose their virginity or wishes they hadn't fucked so much on their deathbed.
If the question were purely biological, interest in sexual pleasure doesn't begin at puberty. There is plenty of scientific evidence that humans are fully capable of orgasm from conception on. There is ultrasound footage of fetuses masturbating in utero. The only thing puberty changes is sperm production in males and the monthly release of eggs in females. For most of the evolution of mankind, life expectancy was 30-40 years and physiologically we developed to become mothers and fathers around age 13. Only in the last century have outside moral and religious convictions raised the age of consent to 18 in the US and other Western countries.
The biological answer to that and other factors has been that the average age a girl begins puberty has actually gone down worldwide. Girls as young as 8 have started getting their period.
If we accept then that age of consent laws are a purely social construct based mostly on Western religious influences; then you have to also accept that whatever age you come up with is purely subjective. Therefore no age of consent law will ever work, as intended, for the masses.
We all learned the pitfalls and perils of sexual relationships by experience, not by the boys basketball coach teaching sex ed for one week in health class. We all began at different ages with different gender preferences regardless of whatever the local consent age was. When I was 7, I got my first BJs from a girl who was 6. Eventually she invited her 4 year-old sister to stop just watching and join in. It follows, then, that we shouldn't have any age of consent law.