Oooh. Good question. Can I take a fully working internet please? No? Once we’ve got the basics to survive, good metal-working is at the heart of agriculture and industry. If I had to choose one thing it would be a design for a good hot oven. I could use it for pottery as well.
Ah well to re-create the world we need to populate it – so assuming the actual planet is intact we would need people to actually do stuff like agriculture and industry or else we’d just die out. So I guess I would have to take a boy! 🙂
Hmmm, this is a tough one! Amy’s answer is great! My question is what do you mean by ended? Do you mean the all life on Earth is demolished or just human civilization? I think that could dramatically change my answer. If it is an end to human civilization, I am with Amy – I would bring a boy 😉 However if all life were destroyed right down to microscopic life, I would bring a bacteria. Eventually evolution would take over and make the “endless forms most beautiful” we see on Earth today. Over 3 billion years of evolution got us to the diversity we see today – the origin of life might be hard – but at least if we have a microbe to start with step 1 is covered!!