To go back to the first part of my quote, quoted by you. In 1859, Charles Darwin wrote something miraculous. His quote is as follows: "If it could be demonstrated that any complex organ existed, which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down."
Well Mr. Darwin, we now know that there are many organs, systems, and processes in life that fit that description. Remember, even in darwin's day, the single "cell" was a black box of mystery. Even at the molecular level it's immeasurably more complex than darwin ever could've dreamed. Like a mouse trap, a removal of any one part of this system(the cell), would cause the entire system to fail immediately.
This principle is called
Irreducible Complexity(ir·re·duc·i·ble /ˌɪrɪˈdusəbəl, -ˈdyu-/Pronunciation Key - Show Spelled Pronunciation[ir-i-doo-suh-buhl, -dyoo-]Pronunciation Key - Show IPA Pronunciation
–adjective
1.not reducible; incapable of being reduced or of being diminished or simplified further: the irreducible minimum.
2.incapable of being brought into a different condition or form.
A car engine is an example of an irreducibly complex system. If a change is made in the size of the pistons, this would require simultaneous changes in the cam shaft, block, cooling system, engine compartment, and other systems, or the new engine would not function. Living things are irreducibly complex, just like a car engine.