Sparkling Pele's hair
Tiny tinfoil confetti!
How about we keep the ability to start fires artificially, but make enough changes so that fires do not start naturally?
There are two main causes that lead to natural fires:
- direct heat from the sun
We need to change the atmosphere such that the direct heat from the sun is greatly reduced, and also to reduce the creation of rapid vertical movements of air masses. In the realms of science fiction, we need very fine
metallic dust mineral fibers dotted with small pirite crystals floating in the air. This amazing fiber is produced without the pirite crystals by volcanoes and can naturally float in the air. In our story it is the result of some very nasty ancient volcanic explosions. The difference from the naturally occurring Pele's hair that I found on the internet, is that we are going to sparkle it with iron crystals. Note that Pele's hair is part of the mineral wools that are considered to be fire-retardants.
The fibers are glassy and sprinkled with highly reflective pirite crystals, thus it will be reflective, increasing the overall albedo of the planet, and it will be most dense in the tropics. The reason for the increased density is that the hotter air, being more rarefied, will cause a local accumulation of the fibers, hence increasing the local concentration, and as a by-product, the local albedo.
The minimum local density of the fibers will also be such that there is never enough difference of electrostatic potential to generate any meaningful spark. Any difference in electrostatic potential will be discharged between the pirite crystals harbored on the mineral fibers. Think of it like living inside a block of metal. All the charges will be distributed in the upper layers of the atmosphere, and ancient hominids will enjoy lightnings only at the boundary between the thermosphere and the exosphere. Considering that Pele's hair has a ridiculously high ignition point, good luck igniting anything up there.
Finally, although it is not part of the atmosphere, I would remove all those piezoelectric rocks, and place all volcanoes that are active during the evolution of mankind well under the sea. Plenty of free-air active volcanoes up to the Mesozoic, fill the atmosphere with the pirite-dotted mineral wool, and then bury all of the under hundreds of meters of water. There too, good luck seeing lava igniting anything.
Finally, to avoid even will-o-the-wisps, we need to add some methane-digesting bacteria to the environment. These otherwise harmless bacteria, which live attached to the floating mineral wool, use the pirite crystals as catalytic agent to degrade methane into CO2 and water, without burning it. This will also take care of local methane spillage.
Humans will need thicker nose hair to filter the
metallic dust mineral wool fibers and prevent some nasty lung carcinomas. I think that natural selection will eventually favor homo-mustachios over homo-sapiens.
The beauty of all this is that we are still in a O2-rich environment. Happy breathing.
PS a big thanks to rek's, John's, and celtschk's constructive comments.