YJ's questions

Recently, YJ was asking many questions that I can't answer immediate.
So, what am I doing now? It is midnight and I am sitting in front of the PC, surfing net, wikipedia, encyclopedia, etc.. but I still cant find good answer. Can some one help?

1. Where human from?
We talked till dinasour time, and din't continue on that.

 2. The structure of the earth, I told him until the inner core, but I forgot what is the inner core made from. I remember it is very hot, but it should be in solid form. but y solid form cant change to liquid form in high temperature? and if it is solid, where the lava came from. I am confused!!
Alright, found the answer: it's made of metal, solid form, and very hot.

3. Lizard's tail - it will drop and grow back, but can it happen many many times? or any limitation?
I can't answer, not in my memory I learn "how many times" before. :P
Found and answer from Wiki: if there are quite young they will only grow back 1 or 2 if there adualts it will grow back 5 to 6 times

Answer from yahoo: it can grow many times, as many as it wants.
hmm.. i am not sure is it a correct answer. let me find out more.

I am refreshing my science. good also.. haha!