QUOTE(ahmetcelik @ Oct 14, 11:51 AM)

I ask for a brief answer; can you build a building without ground floor? you cannot. how can you build a theory without explaining the origin of first living organism? Give me a logical answer
The more interesting question is actually along the lines of:
What convinced single-celled organisms to co-operate/evolve into
multi-celled organisms to the point the multi-celled organisms were
considered a single entity?
That question hasn't really been answered yet and experiments yield a
variety of responses. In some cases, given finite resources
single-celled organisms will co-operatively manage them to the point
where even the resources are considered part of the multi-celled
organism. In other cases mass extinction occurs.
There is an argument that 'life' is merely a series of mass extinctions
on an ongoing scale, with adaptation being the key to survival -- but in
the end everything dies or changes into something so entirely different
from its origins it's no longer recognisable as the same thing.
One attempt to address the apparent altruism of organisms is detailed in
Richard Dawkins book The Selfish Gene. He attempt to show that what would
appear to be a conscious choice of disparate genes to cooperate for mutual
benefit is merely the result of mindless mutation and resulting suitability
(or otherwise) to the environment.
Another of his themes is an effort to explain why there are complex organisms.
The idea comes from an analysis of the total mass of organisms of all
complexities, from the smallest to the largest. There are ~10^30 bacteria on
the earth and less that 10^10 humans, in fact ~10% of your bodyweight is
bacteria! These humble microbes make up ~70% of the biomass of the planet!
So there's not a lot of space down there, so the next trick is to 'cooperate'
(for want of a better word) with another organism and you can both make a new
niche. Soon that niche gets full so some 'clever' organism goes another step
up in complexity.. and so on..
He's once been quoted as saying that Rhincerous genes are among the most hard
working in nature since in order to replicate themselves they first go through
the entire process of building a Rhinocerous in order to do so!
The other common question is how the cell first evolved, one theory in the
Endosymbiotic Theory which suggests the the first cell was created when an
amoeba like organism and a bacteria decide to set up house together.
I stand to correction on some of the specifics, been a while since I
last read up on it trying to be a keen listener :-)