I can't accept that complex species evolve through mutation, I'm sorry. If species mutated to grow arms, legs, eyeballs, etc. then wouldn't we see lots of animals around us halfway through their evolutionary development? All I see are perfectly functioning species, complete in and of themselves!
I'm not being farcical. Correct me if I'm wrong but the accepted belief as to how humans got here is that there was a Big Bang, matter cooled to form the Earth (a rock essentially) and from that simple organisms emerged which became more and more complex over time eventually producing humans. Right?
What I want to know is how even a simple cell (which is incredibly complex in and of itself) came from inert matter?
And why it bothered at all.
Part of the reason that your question isn't being answered to your satisfaction is the the people here are talking about evolution--which describes how life changed to fit different ecological niches. The question you're asking is about a topic called abiogenesis (the original creation of life), which is a completely different thing.
Beyond that, you're not *going* to get an answer that satisfies, because scientists freely and openly acknowledge that we don't know yet how life started--though they're working on figuring it out, and are getting very close.
We are pretty sure about the broad type of thing it must have been though. It would have started with the creation of a molecule (or more than one) that was self-replicating. Through simple, mechanical processes, it would attract other molecules to it, and they would form chains, or maybe networks.
This isn't life--it would probably be simpler and weaker than a magnet, and working on similar principles.
So now the situation is that there's an ocean filled with lots of random molecules, and some of those molecules have a tendency to link together.
Eventually, the chain breaks and now there are two chains, each collecting other molecules that fit it. Again, imagine (and this isn't *literally* true, but is good visual approximation) an ocean filled with random stuff, and few things that happen to be magnetic. They're going to end up clustered together, with more and more things attached to them, eventually becoming unwieldy and breaking up, maybe rejoining, maybe just floating apart...)
Add in mutations. Occasionally, a molecule is going to latch on that isn't exactly.the same, bit is close enough. This is important, because our little proto-DNA has no way to be self-correcting. Now it's attracting this new thing. As this happens to different chains, you start getting different molecules with different traits which will attract molecules in different ways.
Ones which are very strong might attract lots of molecules, but not break, so there aren't many of them. Some that break a lot might not ever form chains at all. In the middle, there are ones that break occasionally but not too often, so they end up with a bunch of true chains floating around.
This continues for a while (a long while) until the loose, floating molecules in the ocean start becoming rare. Now the game just changed. Strongly attracting the molecules and breaking often enough but not too often isn't enough, because there isn't anything around to attract.
But what if...say... One of these chains happens to be made of molecules that change the environment around them. Say, they make the water a little acidic. It's possible that this could break apart the chains around it, and then *those* molecules would be attracted to it.
A chain like that could become dominant for a while, because it would go around breaking up the other chains. Maybe other aggressive sorts happened first, but something like this must have happened at some point, because the obvious defence against it *did* happen.
A chain that exuded something that formed a skin around it would not be vulnerable to the aggressive chain (for now). Now we have a proto-cell.
Of course, if that aggressive one eventually developed a pointy end and was able to pierce the skin and get its acid inside, then the cells would start becoming more rare again...until a different chain, or one of the proto cells develops some other characteristic that changes.the game again.
(A really neat trick would be if the pointy one developed the ability to poke through the skin of the other, and then shot *pieces of itself* into the cell instead of.acid) If the right bits got in, it could alter how the cell replicated, and make more of the aggressive chain instead of more of itself. Of course, that's well on its way to becoming a virus.)
I describe this as if the give and take between aggressive and defensive characteristics is inevitable, and it's not obvious why it should be. Couldn't one just take over? Like, The acid one becomes dominant, but nothing accidentally develops a skin in time to betable to stop its takeover?
It could have happened, but then, where would it lead? You'd have all the oceans in the world filled with chains that exude acid (or whatever) and no free-floating molecules and nothing else.
In our world today, this would mean world-wide extinction, but the important thing to remember is that these things werent alive, so they could have hung out like this for a very long time, never dying. But as they bump into each other and other things, they'd get damaged, break, recombine, and eventually, more mutations would start up again. Eventually, *something* would happen that challenged the monoculture, by sheer virtue of the fact that we're talking about billions and trillions of things happening at one time, over and over again, possibly for centuries. Whatever happened might have had a one in a billion chance of happening, but it only had to happen once. There are lots of "things" happening in the world. Things that have a one in a billion chance of happening happen all the time.
So, either smoothly, or in fits and starts, we have the beginnings of an arms race, and here it gets very difficult to talk about it without using anthropomorphic language because these utterly lifeless things are starting to act in ways that look like...well, like they're acting! Like.they are pursuing goals. But they aren't. They're still random chains of molecules that happen to attract more molecules, and.it just so happens that the ones which attract them in certain ways happen to become more common until something else counters it.
But I hope you can see where this is going: the chains keep changing, according to what happpens to keep them going. Points get pointier, skin gets thicker. One develops a method of propulsion (something like cilia, maybe?) and now everybody needs it.
Eventually, the ones that survive best are the ones that join together in clumps. Maybe one develops.the ability to take energy from the sun and becomes the first chloroplast. Then some of those wriggle their way into other cells, and start existing only as a part of a greater system--the chloroplast is protected by the skin of.the cell, and now the greater system has the ability to use sunlight--algae, then later, plants.
At some point, and how this could possibly happen is not clear, the ones that survive best are the ones that really *can* take go oriented actions. They not only have propulsion, they can speed up when either predator or prey is near.
Out of that very limited sort of awareness, could grow more and more. It doesn't just run at prey, it can predict what it will do. It doesn't just avoid predators, it actively hides.
And now we're starting to see things that most people would call life, and that is where abiogenesis ends and evolution begins.
It's also important to keep in mind that through all of this, there were neverany goals. It isn't somehow "better" to have acquired more useful changes than something else, and nothing compelled every member of a "species" to be changed in ways that had been beneficial to others.
Some of those chloroplast-containing cells clumped together and developed cell walls and became plants, but lots of others have stayed just as they were--algae still exists.
And there's more to say, but that's as much smart-phone writinv as i can handle right now.
