pullup
Homewrecker
The idea of aliens being here is the ridiculous part. If they were here, we'd know it. More powerful cultures in human history (and if they've gotten technology and decided to explore out into the universe then their history is probably similar to ours) tend to destroy less powerful ones. Pre-columbian societies, the Mori-Oris, the Khoisan by the Bantu, potentially even neanderthals, all destroyed by cultures with better guns/germs/steel. Think, why does the white man have all the cargo? You can bet that if they're here, they've got better cargo.
What if Earth was populated by aliens and now we are like a life sized ant farm to them? Hmmm......