All I remember off the top of my head was the tree would alter the elderly people into a new form of protector. When we were exiled we were cut off from the tree and were forced to grow old and die instead


3 Answers 3


This is Protector by Larry Niven. Humans (originally a species called 'Pak') originated from a planet near the galactic core. Pak are born stupid as 'Breeders', but then as they grow older they instinctively eat the root of the "Tree of Life" which transforms them into super-intelligent, super-strong 'Protectors'. Protectors, as the name implies, protect the Breeders.

Humanity is descended from Pak who colonized Earth, only to find that Tree of Life wouldn't grow here, and modern humans evolved from Breeders.

I believe a Protector wouldn't die as long as they continued to eat Tree of Life root, so they were immortal (and very hard to kill on purpose).

  • Protectors are very hard to kill even when they want to die as witness Teela-Protector in Ringworld Engineers. It's also implied that human Protectors are more badass than the original Pak Protectors, since humans have evolved to be smarter and more survivable than the original Pak Breeders.
    – DavidW
    Commented Jul 2, 2020 at 17:13
  • @davidw I recall that simply starving themselves to death was the suicide-means-of-choice for the Pak. Didn't Teela basically fight to lose? It's been a long time since I read that.
    – LAK
    Commented Jul 2, 2020 at 17:16
  • Yes, she fought to lose, but she had to fight; she couldn't just accept her death. (There wasn't enough time for her to starve to death.) Oh, BTW I'm pretty sure it's "Tree-of-Life root" that they eat.
    – DavidW
    Commented Jul 2, 2020 at 17:24
  • 1
    It's a symbiotic virus that grows in Tree-of-life root induces the change to Protector form. Versions that grow in terrestrial root-crops and an airborne variant make their appearance eventually in the Known Space setting, and it's strongly hinted that the tree-of-life virus was used to develop the later-commonly-used longevity drug boosterspice.
    – notovny
    Commented Jul 3, 2020 at 14:35
  • 1
    A Protector isn't immortal, just incredibly long-lived; there's a line I recall in Protector (I think) about a Protector dying of old age. They made very careful notes describing everything, because it was so incredibly unusual.
    – andrewsi
    Commented Jul 5, 2020 at 14:59

Are you thinking of Larry Niven's Ringworld series?

There is an alien race called the Pak who were the ancestors of humans. They were the species Homo Habilis that evolved into modern humans.

When they get old they eat a plant called Tree-of-life that causes them to transform into a powerful and intelligent form called a Protector. Humans are also transformed by eating the plant but the form into which they are transformed is different from a Pak Protector, presumably due to the evolutionary changes humans underwent from the Pak/Homo Habilis.


It's a more tenuous link than the existing references to Niven's Ringworld series, but this also matches with James Rollins's Amazonia where Nathan Rand, heir to the Rand Corporation, enters into the Amazon in search of a miracle cure which has sprung up somewhere in the Amazon Rainforest in South America, especially important because a deadly plague is occurring in the world outside. The ultimate revelation is that there is a tree that is considered to be the source of all life, whose sap does indeed have tremendous curative properties, but also transformative ones, turning members of the tribe (and, as it turns out, Nathan's lost father) into its protectors, unable to live without access to that sap.

  • While Protector, by Larry Niven seems more obvious, this gets my +1 for being the sort of book I might have read a long time ago and distantly recollect rather than one I'd 100% instantly recognise in a description. Commented Jul 3, 2020 at 10:52
  • @Ruadhan2300 It's not a bad book, albeit a bit formulaic. It came up as a comment answer to scifi.stackexchange.com/questions/166912/…
    – FuzzyBoots
    Commented Jul 3, 2020 at 14:00

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