Human extinction might surprisingly not be an all-or-nothing thing. Some fraction of perfect or close copies of humanity in the multiverse (if it exists) might go extinct while others don’t. These copies could be very far away in space – outside the observable universe (level I multiverse), in other bubble universes where cosmic inflation has ended (level II), other branches in so-called Hilbert space (level III) or possibility in other mathematical structures (level IV)(1). If any of these possibilities are true, it suggest that humanity in a non-local sense is unlikely to go extinct in a very long time. My increased level of confidence in the existence of multiple instances of humanity increases my interest in reducing suffering risk relative to reducing extinction risk since my primary reason for prioritizing extinction risk was that I thought we would lose all future value if we (a particular instance of humanity) went extinct.
Additionally, focusing on reducing suffering risk looks more robustly beneficial to me than extinction risks. Reducing involuntary suffering is always good (holding everything else constant) while reducing extinction risk might not be, depending on the quality of the future and your preferences (your E- and N-ratios). Suffering risks are also more neglected than extinction risk (2). Having said that, it would be an inconceivable tragedy if it will turn out that consciousness, which seems to be the ultimate source of all value, only emerged once in the entirety of existence and never reached anywhere close to its full potential. This seems like a real possibility, so I’m sympathetic to the cause of reducing the risk of extinction.
(1) See Max Tegmark’s four levels on Wikipedia. From what I gather, each level is more controversial than the previous one, with the first one being uncontroversial among cosmologists and the last one highly speculative. Even if level I is uncontroversial, we don’t know if it is big enough to host other instances of humanity but cosmological evidence suggests that it could be infinite, from Wikipedia: ”Arguments have been put forward that the observational data best fit with the conclusion that the shape of the global universe is infinite and flat, but the data are also consistent with other possible shapes.”
(2) In “Against Wishful Thinking”, Brian Tomasik explains why he thinks people don’t pay enough attention to the risk that suffering could get greatly multiplied in the future.