Evolutionists (atheists or otherwise): if Darwin's theory was true, ...?

because we didn't evolve!

I mean we did somewhat but not how evolutionist think.

it takes a couple of thou sad years to evolve into humans..."cavemen" are from 4+ billion years ago.

Humans would have been walking around long before what is documented if that be the case

Ok, lets say that a creature has a mutation that gives it two hearts. A rather rare spontaneous mutation but oh well. This creature now walks the planet and has two hearts. Its off spring will have two hearts. However, does this creature have a greater chance of reproducing? The two hearts is only really useful if one heart is damaged. Normally, that kind of damage comes from a pretty intense injury. Even if there was a second heart available that intense injury would still probably kill the animal as it would probably bleed to death or have a massive infection later on. So, a second heart would not really help too much. Probably a one in a million shot where two hearts would be beneficial. Lets look at the flip side. Two hearts will require more energy to work than one heart. That will mean the animal has to eat more. Not very helpful to the whole survival thing. Also, these two hearts need to work together. If they beat wrong then they could actually work against each other. The body would need a system to regulate both of the hearts and that would also require more energy. Also, a more complicated system is more prone to failure. Two hearts would actually be a hindrance. In the end, having two hearts would not give any edge to the animal but would in fact make it a tad bit harder to survive. The genes giving an extra heart would probably die out and the animals with one heart would survive and reproduce.

For the same reason that birds that migrate to islands without predators often lose their ability to fly. It costs energy and resources to maintain any bodily structure or ability. If that investment of energy and resources doesn't pay off in increased progeny, then the structure or ability will be selected against and lost.

On the other hand, if an omnipotent God had designed us, he presumably wouldn't have to worry about the payoff of invested resources. He could just decide we'd always have enough resources to support two hearts. So assuming two hearts would occasionally come in handy, it's much easier to see why evolution only gave us one than it is to see why God did.

Why stop at 2? Why not 3 or 4. Or 12.

We evolved to only have one heart because having more than that is detrimental to a being's survival. People (and animals) who are born with more than one heart don't live that long; certainly not long enough to reproduce.

we could ask this question of every body part.

"why not have 2 of everything in case one fails, we have a backup"

that's not really how evolution works. Evolution comes about when people/animals/other life forms have to adapt to changing environments. The signs of modern evolution are all around us, it's just the majority of people believe in a higher power and wouldn't inconvenience themselves to bother finding out and learning more about it. Not to mention no one really reads the studies of scientists anymore.

Because there were no mutations that resulted in humans having 2 hearts. You have misunderstood the notion of evolution, yet again. Creatures didn't evolve traits IN ORDER to make them live longer, they evolved traits at random, and those with survival traits lived long enough to propagate their bloodline, passing those traits to the next generation.

We haven't finished evolving, yet. So maybe in 2 or 3 thousand years from now, the human body will have two hearts.

Evolution does not create perfect organisms. However, a god certainly should not have had the oversight for many of the flaws in the human body.

Evolution is chooses necessary traits.unless everyone begins to have heart problems, only necessary traits will be acquired

Because we don't need them....

Besides, we're not even done with evolution yet

If God wanted us to live longer to preach his word why didn't he give us another heart and brain to be able to do that?

"we need a pair of almost everything except those to survive"

we have 1 brain, 1 heart, 1 liver, 1 galbladder, 1 small intestine, and 1 large intestine.