KeepersAre we a protected zoo? The zoo hypothesis

How does the zoo hypothesis explain the Fermi paradox? This page covers the Drake equation, the Great Filter and other real science behind the game.

Alien civilizations may have been everywhere for a long time and are simply avoiding contact with us on purpose, treating Earth as a nature reserve. This is the "zoo hypothesis", proposed by John Ball in Icarus in 1973, and it is one explanation of the Fermi paradox. The game's "Keepers" channel turns the hypothesis into a concrete story: another pair of eyes has been watching Earth, and for longer than you have.

This page covers the real parts: the zoo hypothesis and its "cousin" the planetarium hypothesis, the Drake equation, the Great Filter, and real-world precedents for "no contact". Then it outlines the game's scenario. The Keepers are fictional.

Real concepts around the hypothesis

Zoo hypothesis: alien civilizations may have been everywhere for a long time and are simply avoiding contact with us on purpose, treating Earth as a nature reserve (Ball, Icarus, 1973).
Drake equation: in 1961, at a meeting at Green Bank Observatory, Frank Drake wrote an equation that splits the number of communicating civilizations in the Milky Way into seven factors multiplied together. Most of the factors can still only be guessed.
Planetarium hypothesis: in 2001 the science fiction writer Stephen Baxter proposed in the Journal of the British Interplanetary Society that the starry sky we see might be a carefully arranged backdrop. This presupposes a civilization able to manipulate matter and energy on the scale of galaxies.
Great Filter: in 1996 Robin Hanson proposed that on the way from dead matter to a galaxy-spanning civilization, there must be at least one extremely hard step. Is that step behind us or ahead of us?

"No contact" in reality

In 1987 Brazil, with Sydney Possuelo leading the effort, set up its department for isolated indigenous peoples. From then on the government stopped actively contacting isolated tribes and stepped in only when they faced serious threats. Earlier contacts had often carried deadly diseases to them. This is a human-run, zoo-style protection, and the real-world counterpart of the game's line "the wall is not there to keep you in, it is there to keep what is outside from getting in".

How to tell who is self-aware, and who qualifies

Mirror test: in 1970 Gordon Gallup gave chimpanzees the mirror test. While they were anesthetized he put a dot of dye on the forehead, and chimpanzees who woke and looked in the mirror touched their own foreheads. Recognizing oneself is seen as one sign of self-awareness.
Marshmallow: the marshmallow experiments of the 1960s found that children who could wait a little longer for a second treat did better in school later. A 2018 replication with more than 900 children found that, after controlling for family background, the association almost vanished. A test may measure less than you think.

The two have something in common: how does the party being observed prove it has matured enough? The "exam paper" on which the Keepers grade the main civilization in the game asks similar questions.

The idea in the game

What follows is game lore. The channel is discovered by unlocking "Observer's telescope" in the Tree of the Beyond, or by finding at least 5 other civilizations in the same universe (with the main civilization having built a Dyson sphere). In the scenario, the Observer finds a bias in all its observation records that cannot be removed: another pair of eyes has also been watching Earth.

The mechanic is the exam paper. The Keepers are grading the main civilization, and the questions are scattered across the universe: whether you fired first, whether you protected life through mass extinctions, whether you cooperated with other civilizations, whether you let self-replicating machines get out of control, whether you survived a civilizational crisis. The higher the score, the faster the channel's output. At 60 points they will block one strike from far away on the main civilization's behalf, once only.

In the scenario, the Keepers were once the ones being kept. They open the door a crack and pass something through. The channel has three endings: Graduation, Keep watching and Raise the wall. All of this is fiction.

Childhood's End (Arthur C. Clarke, 1953): the zoo hypothesis (Ball, 1973) holds that alien civilizations may be deliberately avoiding us, which is one explanation of the Fermi paradox. In the novel, alien "Overlords" suddenly descend and bring humanity peace and prosperity, while actually waiting for humanity's next generation to become something far beyond the individual.

The studies below concern the search for extraterrestrial civilizations, the classification of civilizations and the Fermi question. They are related real science, not evidence that Earth is being watched.

A proposal to use radio telescopes to listen for alien signals near the 21 cm frequency of hydrogen, which started SETI (Cocconi and Morrison, Nature, 1959).
Civilizations classified into three types by the energy they can use: planetary, stellar and galactic (Kardashev, Soviet Astronomy, 1964).
If extraterrestrial civilizations were common, they should long ago have spread across the Milky Way, so we may be the first (Hart, Quarterly Journal of the Royal Astronomical Society, 1975).

Real basis

Zoo hypothesis: In 1973 Ball proposed in Icarus: alien civilizations may have been everywhere all along, deliberately avoiding contact and treating Earth as a reserve.
Drake equation: In 1961 Drake wrote down an equation at a meeting at Green Bank Observatory, splitting the number of communicating civilizations in the Galaxy into seven factors multiplied together. Most of them can still only be guessed.
Planetarium hypothesis: In 2001 science fiction writer Baxter proposed the “planetarium hypothesis” in the Journal of the British Interplanetary Society: the starry sky we see may be a carefully arranged backdrop. It requires a civilization that can manipulate matter and energy on galactic scales.
No contact: In 1987 Brazil, pushed by Sydney Possuelo, set up its department for isolated indigenous peoples. Since then the government no longer initiates contact with isolated tribes and steps in only when they face serious threats. Earlier contact often brought deadly disease.
Mirror test: In 1970 Gallup gave chimpanzees the mirror test: dye was put on their foreheads while they were anesthetized, and chimps that touched their own foreheads when they looked in the mirror after waking. Recognizing oneself is seen as a sign of self-awareness.
Marshmallow: The 1960s marshmallow experiments found that children who could wait a bit longer for a second treat did better in school later. A 2018 replication with over 900 children found that once family background was controlled, the association almost vanished. A test may measure less than you think.
Great Filter: In 1996 Hanson proposed the “Great Filter”: between dead matter and a galaxy-spanning civilization there must be at least one extremely hard step. Is that step behind us, or ahead of us?
The children: In Clarke's 1953 Childhood's End, the Overlords land on Earth and wait for the next generation of humans to become something far beyond individuals.
Childhood’s End (Arthur C. Clarke, 1953), the science: the zoo hypothesis (Ball 1973) holds that alien civilizations might be deliberately avoiding us, one explanation of the Fermi paradox.

Related research

These studies relate to this topic but are not direct proof of this page.

Searching for interstellar signals: Two physicists suggested listening for alien signals with radio telescopes near hydrogen's 21 cm frequency, launching SETI.
Source: Cocconi & Morrison, Nature 1959, "Searching for interstellar communications"
Scale of civilizations: Sorts civilizations into three types by the energy they can use: planetary, stellar and galactic.
Source: Kardashev, Soviet Astronomy 1964, "Transmission of information by extraterrestrial civilizations"
Where are they?: If alien civilizations were common, they should already fill the galaxy. From this Hart argued that we may be the first.
Source: Hart, Quarterly Journal of the Royal Astronomical Society 1975, "An explanation for the absence of extraterrestrials on Earth"

Game lore (fictional)

Node “The wall”: The wall faces outward: it blocks what is outside, not you.
Node “Exam paper”: The questions are scattered across the whole universe. You don’t know you are being tested.
Node “Who the Keepers are”: They were once the ones being kept.
Node “A crack in the door”: They open the door a crack and pass something in.
Node “Results”: The day the scores are announced.
Channel ending “Graduation”: The Keepers walk inside the wall for the first time. They bring no gift, only one sentence: you can take care of yourselves now. This run, the main civilization’s “Interstellar civilization” output +12%.
Channel ending “Keep watching”: The Keepers close their records and say: let’s watch a while longer. The wall is still there, only a little lower.
Channel ending “Raise the wall”: The Keepers raised the wall. From then on, when the main civilization looks at the sky, what it sees may be a curtain.
Summary of the novel Childhood’s End: A group of alien “Overlords” suddenly arrive and bring humanity peace and prosperity. They are in fact waiting for the next generation of humans to become something far beyond individuals.

See it in the game