Maxperson
Morkus from Orkus
Um....
Humans only occur by action of humans. We do not spontaneously generate and spring forth from spoiled meat, or something - it requires human action to create a human. And even more human action to craft another human that talks and does mathematics and engineering...
I'm going to have to have a serious conversation with my mother about storks.
Seriously, though, reproduction is a natural act. It's not as if we have to go smelt a bunch of metal to forge us some babies.
Cars only occur by action of humans....
I agree with the general posit that there is a practical dividing line between natural occurrences and the actions of sentient beings. But this logic doesn't hit the mark.
It takes more than an act to make something unnatural, though. See my comment on the difference between an ant hill and a beehive. Yes reproduction and cars both require human acts, but one is an act of nature and the other involves unnatural acts.