the great depression was a time of economic failure in many countries, so the puchasing of drugs and doctor visits was greatly reduced and made many sicknesses escalate couple this with the fact of poor living condition and its no wonder why sicknesses escalated to the point they did.
It will evolve during trade.
Not to a normal evolution, but Pokemon that can do so can Mega Evolve during battles.
It can only evolve during daytime and with a oval stone.
Riolu evolve by happiness during the day.
Evolve Eevee during the day
During trade it must hold dragon scale to evolve.
Brock's Marshtomp does not evolve during any episodes.
It doesn't evolve at a specific level, but it will evolve when leveled up with high happiness during the day.
It doesn't evolve normally. If you have it hold a Tyranitarite, though, it can Mega Evolve during battle.
Most evolve by getting to a certain level, some evolve on a high level of friendship during the day or at night or just by friendship, some evolve with stones, some at special land marks, some during the day, some at night, and some don't evolve at all.
Sneasel will evolve during the night if holding a Razor Claw.
Yes, certain Pokemon can evolve at night (only at night; all Pokemon can evolve during the night except for day-only Pokemon like Espeon) whether holding an item or simply with Max Happiness. These Pokemon can only evolve at night time:Eevee - Evolves with maxed out Happiness during the night; it'll evolve into Umbreon.Sneasel - Let it hold a Razor Claw and level it up in the night. It'll evolve into Weavile.Gligar - Let it hold a Razor Fang and level it up in the night. It'll evolve into GliscorChingling - Max out its Happiness during the night and it'll evolve into Chimecho.Amaura - Level it up at level 39 during the night and it'll evolve into Aurorus.Pokemon who cannot evolve during the night are:Eevee (To Espeon), Budew, Happiny, Riolu, and Tyrunt.