Or the "zoo hypothesis"[1] is true and we're quarantined off on our little planet out here. I figure we're like the people on North Sentinel Island[2]. We haven't even invented fire, and we kill anyone who tries to shows up on our island. We're so remote that the local authority in the area has declared our Island a protected zone, just as India has with North Sentinel Island. We occasionally see helicopter and try and shoot arrows at them.

1.https://en.wikipedia.org/wiki/Zoo_hypothesis

2.http://www.odditycentral.com/travel/north-sentinel-island-th...