The threat from extraterrestrials is not Them, it's Us. In this provocative exploration of what we know of the search for intelligent life in the universe, Alexander Wendt explains why, despite the common assumption that discovering a non-human intelligence in our solar system would bring humanity together, there is a real chance that--even without direct contact--it could cause states and the international system to implode in chaos and violence instead.In 2021, the Pentagon announced that UFOs, now Unidentified Anomalous Phenomena (UAP), are not only real, but a potential threat to national security. The Pentagon did not say who the threat was from, what exactly the threat was, nor did it mention extraterrestrials (ETs). Yet this finding raises several existential questions. How would human society react to the discovery that we are not alone in our solar system? Would the discovery of ETs locally unify humanity under a world state, or would disagreements on how to respond to an alien presence tear us apart?In The Last Humans, Alexander Wendt explores a future scenario in which global authorities conclude--and disclose--that UAP are flown by ETs, and what this discovery would mean for both human security and the international state system. Wendt contends that this situation would indeed be a national security threat, but not of the traditional, military kind. The realization that states are impotent in the face of vastly superior ET power would be an ontological shock to modern civilization, given the anthropocentric assumption that "We Are Alone". Taking UAP and potential ETs seriously would call into question the legitimacy of the modern state, the social contract that underlies it, and the global civilization built around it.By considering how people might respond to the discovery of ETs, Wendt shows how attachments to the territorial state could weaken and ultimately collapse anthropocentric sovereignty from within. He argues that this would throw humanity into a twenty-first century version of Hobbes' war of all against all--even if ETs never intervene in human affairs. Through this prism, The Last Humans makes the case that the threat of UAP is not alien conquest, but a global identity crisis in which humans discover a powerful new reason to hate each other.