(This post co-authored by Robin Hanson and Katja Grace.)

In the Battlestar Galactica TV series, religious rituals often repeated the phrase, “All this has happened before, and all this will happen again.” It was apparently comforting to imagine being part of a grand cycle of time. It seems less comforting to say “Similar conflicts happen out there now in distant galaxies.” Why?

Consider two possible civilizations, stretched either across time or space:

• Time: A mere hundred thousand people live sustainably for a billion generations before finally going extinct.
• Space: A trillion people spread across a thousand planets live for only a hundred generations, then go extinct.

Even though both civilizations support the same total number of lives, most observers probably find the time-stretched civilization more admirable and morally worthy. It is “sustainable,” and in “harmony” with its environment. The space-stretched civilization, in contrast, seems “aggressively” expanding and risks being an obese “repugnant conclusion” scenario. Why?

Finally, consider that people who think they are smart are often jealous to hear a contemporary described as “very smart,” but are much happier to praise the genius of a Newton, Einstein, etc. We are far less jealous of richer descendants than of richer contemporaries. And there is far more sibling rivalry than rivalry with grandparents or grandkids. Why?

There seems an obvious evolutionary reason – sibling rivalry makes a lot more evolutionary sense. We compete genetically with siblings and contemporaries far more than with grandparents or grandkids. It seems that humans naturally evolved to see their distant descendants and ancestors as allies, while seeing their contemporaries more as competitors. So a time-stretched world seems choc-full of allies, while a space-stretched one seems instead full of potential rivals, making the first world seem far more comforting.

Having identified a common human instinct about what to admire, and a plausible evolutionary origin for it, we now face the hard question: do we embrace this instinct as revealing a deep moral truth, or do we reject it as a morally irrelevant accident of our origins? The two of us (Robin and Katja) are inclined more to reject it, but your mileage may vary.

(This is cross-posted at Overcoming Bias.)