Do our Brothers Exist? The Unknown Tribe Paradox

“We have seen the signs.” Footprints, tracks through foliage, occasional glimpses of fleeting figures – there is no doubt. “They exist. Our brothers exist.”

Guardian Jul 2004

What is the interviewee talking about here, the Yei, Sasquatch?

They were talking about a previously uncontacted tribe in Peru.  We are not ‘uncontacted’ in the sense that we know they exist but don’t arn’t to be contacted but where we don’t even know if the tribe exists or even what its name is if it does.  Of course  such rumors often turn about to be untrue, to be other contacted tribes, or people just dressing up to create fake magazine stories, even false rumors to protect virgin forests.  Skeptics would say there is no evidence, but absence of evidence is not proof of absence.  At some point all tribes in isolated areas were uncontacted and there discovery is the black swan event that proves they do exist.  A tribe may be uncontacted and unknown because they don’t want to be known, they might have observed from a distance how deadly modern man is.  Though no crazy xenobiology tub-thumper I do get impatient with the argument that goes x cant exist because we have found no bodies, no roadkill etc. especially when if the creature if sentient, and if it exists, may have learned from its ancestors to retreat as far from settlements and roads of genocidal man as possible. Survival only possible through invisibility.

This is the paradox,  can we assign a likelihood other that 0 or 1 to the existence of an unknown that can only be either 0 or 1? Yes we can we can assign a probability to a state of the world that never existed and never can exist.  This poses problems with the Laplace/Keynes view of probability because we dont even know if black balls exit in the urn at all.   It also poses problems to both the Bayesian and frequentist interpretations of probability. It makes no difference run something multiple times if it either exists or doesn’t exist in every case and we were looking in the wrong place.  Similar with anterior probabilities either we are wrong or we are right.  Is this not then a logic state rather than a probability?

Consider a remote space where an unknown creature may or may not exist and we have no evidence that it does other than unconfirmed rumor. The absence of evidence is in itself prior information from which we can construct a model.  The higher the population the more likely they are to be spotted,  If the only food sources are mushrooms and guinea pigs from what we know about the observed values of either we can construct a mathematical model of how likely it is the creature exists at any level of population.  So if the number of mushrooms could only have occurred by chance 10% of the time then there is a 90% probability that the creature exists.  You can get such quanta of probabilities at any physical scale.

How then do we interpret the meaning of 90%?  We cannot say if we look for the creature 10 x we would find it once. It is not an experiment we can repeat 10 times. This is another form of the ergodic fallacy,  It is better to say we have an expected error of 10%, an error based on our uncertainty of the state of the world due to incomplete information about all parameters.  We expect to be wrong 10% of the time and if someone offers us odds of 20:1 it is therefore an example of ole peter’s concept of rational leverage and to accept that bet.


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