If you think that the poster is an effective argument for evolution, then you may not quite grasp the profundity of gravity either. That things fall is obvious. That all things made of stuff are attracted to all other things made of stuff, not so much.
That there is a predictable relationship between all matter in our universe is a bigger deal than many who "believe in" gravity grasp.
There may be some confusion about religion, too, a confusion exacerbated by those who would distinguish spiritual from religious.
You need time for complexity to evolve, and time we have.
But complexity is not the "goal." We are not headed towards a higher being, just a different one, possibly more complex, possibly not.
When a child gets this, do not be surprised if she goes into a trance for a day or a week. A child who gets this will feel her universe shift under her feet, her place redefined, her sophomoric cynicism squashed by awe.
Some folk call that a religious feeling, and it is.
Grasping evolution changes our relationships with the living world around us.
Darwin's reasoning does not need to supplant God, and for many it does not. The theory of evolution does, however, supplant the need for a superior consciousness (or any other sort of consciousness) to guide the development of the beasts we call human.
It takes more than a class or two for a kid to get this, but there's no mistaking when one does. She's the one who's gone silent, stunned.
Natural selection is deceptively easy to grasp. It's not the concept that most of us resist. It's the implications. Evolution has no goal.
We're no more evolved than the earthworm, the mushroom, or the E. coli in our guts.
The jumping lamb is from Life is Physics Not Mathematics.
It's all good--we're all a part of this universe thing, and that's just awesome!