Question

I know there are many explanations as to 'where we come from' - but what scientifuc explanations are there?

The question of "where we come from" is central to astrobiology and is related to almost all of biological science. But it is also a very broad question, and I am not sure which parts of the story you are asking about. If you are interested in the immediate origin of humans (homo sapiens), our ancestors arose in Africa several million years ago as a branch of the evolving family of apes (many of which, including our direct ancestors, have since become extinct). The most closely related surviving group of apes are the chimpanzees. As we trace our lineage back through the long evolution of life on Earth, there are a number of key events: the emergence of life on land, the development of multicellular life, the invention of sex (combining genetic material from two parents rather than one), the emergence of the Eukarya domain, the invention of photosynthesis, etc. If you are primarily interested in the ultimate origin of life on Earth 4 billion years ago, then science has not yet provided a detailed scenario for the emergence of the first living things. Various aspects of this question are discussed in other more specific answers posted here. You might want to try the headings "origin of DNA" or "early Earth" or "Oparin" to look up those answers. I also recommend the recent book by Nobel-prize winner Christian de Duve called "Life Evolving: Molecules, Mind and Meaning".
March 26, 2003