Birds and the bees... do I wait for signs the kid is ready or should I be proactive?

I have a 10.5 yo son. He shows no signs of being aware of sex. He’s kind of an aloof kid and may be a little immature for his age. I’ve been kinda waiting for some sign that it’s time to open the conversation, but nothing so far. At some point before he’s ..... 30 ..... :) I’ll need to stop waiting at just jump into it. Am I there now? TIA! via /r/Parenting http://bit.ly/2HyTGfL