Did Lovecraft simply present the idea that aliens created the life on earth or did he also present the idea that they helped us evolve or somehow sped up the process? I'm not very well informed in the literary world.
Short version:
In "At The Mountains Of Madness" The Elder Things are the source of all life on Earth, mostly for their food/amusement/use. They appeared around a billion years ago.
They had a race of slaves called Shoggoths that could turn into anything with a thought. They used them as beasts of burden, tools, even building material.
When the climate of Earth started to change it weakened their civilization, which led to the Shoggoths rebelling. Eventually the Elder Things retreated to an underground sea.
Millions of years pass, and what they originally created eventually becomes humans.
Humans plan an expedition to Antarctica in 1930, where a giant mountain range is discovered to be the walls to an ancient city. Inside the city the explorers find carvings on the walls that depict the history of what I just described. The carvings also show something existed on Earth prior to the Elder Things, that they feared and hated. It was trapped behind the mountain walls.
Eventually the explorers find some Elder Things and Shoggoths and that doesn't go too well. Lastly as they're leaving one of the two surviving explorers looks back and sees something trying to escape the walls of the city....whatever it is makes him lose his mind. The story ends with the final sane explorer pleading with scientists to never go to that region again.
Fred.