I've often talked about how life has evolved on four specific paths that can be called food in / waste out. Two paths or options to food in. Two paths or options to waste out.

The four options are
1 Nurturing* taken in.
2 Non nurturing (waste) blocked out.
3 Nurturing held in
4 Non nurturing (waste) excreted out.

*Nurturing is anything that helps that organism survive in that
environment.

No matter how life evolved, each step is one or more of these
4 basic options or paths of natural selection.

I now suggest that this has a fundamental biological basis.
Food in relates to metabolism
Waste out relates to replication.

1 Nurturing taken in,
3 Nurturing held in.
would both relate to metabolism

4 Non nurturing (waste) excreted out
would relate to replication
(replication would have evolutionary benefits for parent
genome and/or cell too).

We can go further and suggest that
the cell membrane would relate to

1 nurturing taken in
2 non nurturing blocked out
4 non nurturing (waste) excreted out.

So when we talk of almost any of the origin of life definitions -
we are really talking about aspects of food in waste out.

And when we talk of food in waste out, we are talking of
metabolism, replication, and all the other aspects that
define life.

thoughts?

Tom Hendricks
http://www.daviddarling.info/encyclopedia/U/UV_origin_of_life.html