[andylei]

> what humans can realistically create with their own hands from nothing

could medieval blacksmiths really create a sword from nothing but their own hands? how would they get the iron? would they have the knowledge locate veins of iron and then mine that iron? could they build the kiln and forge the equipment necessary for forging

arguably, by this standard, even farmers could not farm. farmers may know how to plant their crops, but without current crops to gather seeds from, would they know how to find the strains of plants that suit farming and then gather the seeds from those plants?

[bwarp]

Well actually, I reckon yes. Much to my parents' latent terror (I didn't tell them until they came back from holiday), at the age of 15 a friend and myself built a small blast furnace using some ceramic pots, bits of stone lying around and a hoover. I managed to get 50g of what looked like pig iron out of that bugger before it basically fell to bits and set fire to the lawn. That was from about 2kg of ore I found at the bottom of a cliff face next to a beach at Skegness. Was great fun! (flux was limestone from the shed, coke was 3 large bags of barbeque charcoal)

I'm sure that and the rest of the process wasn't beyond people with a higher budget and requirements...

As for plants - it's all knowledge and experience. There is no abstraction. Eat this, don't eat that. I grow quite a few edible plants myself and there is little abstraction.