Task: Question Answering
Input (English): Passage: In 2077, sixty years after a war with extraterrestrials that devastated Earth, humanity has relocated to Saturn's moon Titan via a giant space station called the Tet. Gigantic offshore fusion energy generators drain Earth's oceans to power the colonies on Titan.
Led by mission controller Sally and guided by his housemate and communications partner Victoria "Vika" Olsen, "Tech-49" Jack Harper regularly leaves his tower post to repair downed combat drones that guard the regions and generators against the alien scavengers. Although his memory has been wiped, he has had recurring dreams and visions of being on the observation deck of the Empire State Building with a dark-haired woman. He also collects the occasional artifact that he finds from humanity's past. Vika is concerned about Jack's curiosity, questioning whether they are still "an effective team," and encouraging him to do his job, so they can join the others on Titan soon.
After scavengers destroy a generator, Jack discovers that they have been using the Empire State Building's antenna to transmit coordinates to outer space. While taking a break at his secret lake house retreat, he watches a crash-landing module of a pre-war spacecraft called the Odyssey. Thinking that the ship contains aliens, he investigates, only to find humans in stasis chambers. One of the humans is the woman from his dreams. Jack protects her chamber from a drone that destroys the others, and later, revives the woman, Julia Rusakova, who makes Vika instinctively jealous. Jack and Julia return to recover her flight recorder, but are captured by the scavengers. They are taken to their headquarters at the Raven Rock Mountain Complex, and the scavengers are revealed to be human survivors. 
Question: What is the species of the beings who destroyed the generator?
Output (English): human.