Artificial machines can't duplicate natural machines
The kinds of machines that humans construct will never be able to fully simulate the structure of natural machines. In a natural machines—unlike artificial machiens—each and every part, no matter how small, is tailored to the into the whole.
Artificial machines by contrast always contain some parts that aren't tailored to the ends of the whole.
Thus, an artificial machine will never be as complex as a living organism.
Gottfried Leibniz (1714).