The human cost of World War I was

The human cost of World War I was enormous. More than 9 million soldiers and an estimated 12 million civilians died in the four-year-long conflict, which also left 21 million military men wounded. "Many of them were missing arms, legs, hands, genitals or driven mad by shell shock," says historian Adam Hochschild

it would have to be gasioline

answer:

it caused mass african migration, african populations to grow, african empires to topple, and racism against slaves to emerge.