Which simple machine do feel has had the greatest impact on mankind?

The light bulb :P Where would we be without the light bulb? :)

Grace summers i think the wheel and axle has the greatest impact because without it we wouldn't have steering wheels for cars.Therefore making life harder. Or inclined plane becaues without it we wouldnt have stairs. therfore the world will result to elevators but building elevators cost more and wil take part in our eco-friendly world <3