B a very large molecule made of smaller molecules
It might be an ecosystem
Hope this helps
Our most distant predecessor is Australopithecine who lived about up to 3 million years ago. Then homo habilis and homo erectus evolved, but they have been living more less at the sime time - it's unsure which of them was the first one (it was about 2.5 million years ago). Homo sapiens appeared about 200 thosuand years ago.