My friend read this science fiction story as a kid, probably written prior to 1970. Forgive me it's a second hand description: Earth is visited by aliens. The aliens note that every race in the galaxy is "unique" in some way; but humankind does not seem to have anything that makes our race unique. Eventually when a character in the story dies, and the aliens don't know what death is, the aliens realize humans are the only species they have ever known that dies! First, Thank you all! Talked to my friend who added this clarification - in his own words: You got it almost all correct in your story synopsis. However, in the story after an allotted time-period where humans are given the chance to display their uniqueness and fail, the alien envoy is being given a right back to its ship and has to stop for a funeral procession. It asks what is going on and when described it is mentioned that the person being honored/intured had died. Surprisingly, the alien doesn't seem to understand the concept of people dying so it is told exactly what happens when a being dies and the alien exclaims something like, "That's what humans do that's unique!" Of course, this means that death, our eternally accepted nemesis, proves to be the sole savior of our race in terms of entering the confluence of sentient beings.