Even these “simpler” forms of hearts and brains had to be fully functioning for their organisms to survive. How many steps were needed to “evolve” these simple structures?
If God is unnecessary for nature to climb “Mount Probability”, as Dawkins calls it, how great a leap is it for one to conclude that a god is merely a figment of man’s imagination? A baby step, for sure. Why do you suppose that so few young people have Faith in a Supreme Intelligence? Old Charles has been stuffed down their throats in a non-stop, full court press, that’s why.
There are animals without any brains or hearts at all. Jellyfish, flatworms, etc. Pumping blood and organizing nerve impulses from a central location are nice but clearly not required for life to exist. In ours and most other cases they evolved over time because they were beneficial in some way. As I have said, those who disagree with evolution typically do so because they don’t understand it. How many time have I heard the argument that certain organs must have just popped into existence without having evolved from something simpler? It simply implies a lack of understanding.