The Fermi Paradox: Too Rare? III

In my previous post, I had discussed this list up to the colonization of land.

  1. Stars I
  2. Planets I
  3. Origin of Life I
  4. Origin of Photosynthesis II
  5. Multicellularity II
  6. Colonization of Land II
  7. Intelligence
  8. Technology
  9. Abstract Science

I will be finishing off this list.


That is difficult to define, especially human-scale intelligence. I think that it reasonably includes:

  • Deliberative reasoning in addition to intuitive reasoning
  • Self-awareness and self-recognition — a conception of oneself
  • Being very social
  • Theory of mind — what others are thinking
  • Language with full-scale syntax (arrangement of symbols), and not just individual symbols
  • Transmission by learning of a large body of ideas and practices — cultural features
  • Consciousness (???)

Only a few species come close to us, notably chimpanzees and dolphins — and chimps are our closest relatives. Some chimps have been taught sign language, but the most they do beyond individual signs is two-sign phrases and not human-language full-scale sentences. We can recognize ourselves in mirrors from an early age, but only a few other species can, like chimps and dolphins and elephants and Eurasian magpies (Pica pica).

Using found objects as tools is more widespread, though only a few species are known to make tools out of objects. Species like chimps stripping leaves off of twigs and then using those twigs to fish for termites, and New Caledonian crows (Corvus moneduloides) bending sticks and wires to make hooks.

In general, evidence of high intelligence correlates with having relatively large brains, and such brains have evolved a few times independently. However, no other species possesses human-scale intelligence, though some cetaceans may come close. Large brains can be energetically difficult to maintain, a further difficulty. So the emergence of human-scale intelligence remains very iffy.


Living on land is very helpful for developing technology with interstellar reach, and we have an additional helpful feature: our hands. Each hand has five independently movable fingers, and we can create two kinds of grips: fingers – palm and thumb – another finger. This is an elaboration of the sorts of hands that our primate ancestors and relatives have, and grasping organs have independently evolved several times: some arthropods’ pincers, elephants’ trunks, cephalopods’ tentacles, some New World monkeys’ prehensile tails, some birds’ feet, etc. So there may not be much problem in evolving that.

Turning to the main subject, humanity foraged for most of its existence, hunting and gathering. Agriculture was a latecomer, though it was separately invented in several places over the last 12,000 years, the Holocene.¬† I’ve seen the theory that the Holocene had a climate stable enough for agriculture to get started, and that the climate had previously been too unstable. This suggests that agriculture could be difficult to develop.

Agriculture has the nice feature of supporting much larger population densities than foraging can, and it eventually makes possible specializing in various technologies, thus improving their development.

Writing is next, and it was apparently invented only a small number of times. But once it was invented, it was repeatedly borrowed, and knowledge of its existence sometimes provoked the invention of writing systems: stimulus diffusion. So its origin is rather iffy.

Technology advanced slowly over most of humanity’s history, but its advance speeded up in recent centuries with the development of abstract science.

Abstract Science

Or theoretical science, as distinct from technology. It got started in Classical-era Greece, and it continued into the post-Alexander Hellenistic era and then into the Roman Empire. However, the Roman Empire had a period of strife and civil war and fragmentation in the third century, and that interrupted the development of science. It did not restart for a thousand years, and even then, it was rough going at first.

Though it has been enormously successful, it has involved some very counterintuitive theories and practices, and also amounts of abstraction that many people find very difficult. Abstraction like advanced mathematics.

So it may be difficult to evolve the capability for abstract science. In fact, Robin Dunbar’s “social brain” theory suggests that intelligence emerged for dealing with other group members and navigating social relationships. However, there seem to be a subset of people who are much more capable of abstract thought, people with high-function autism or Asperger’s syndrome. So even in the earliest human societies, such people could have acquired and provided useful expertise. This is something like Robert Sapolsky’s schizotypal-shaman theory, that schizophrenia has persisted because mild cases had long been useful for acquiring certain sorts of expertise.

So the emergence of the capability for abstract science is another iffy issue, even leaving out its dependence on large-scale societies, something that agriculture makes possible.

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