What conditions in a ecosystem, specifically where on a food chain and what kind of diet, would likely result in a creature gaining the necessary brain structure, and opposable digits, to become sentient? I am aware that defining sentience is quite difficult, so feel free to use you own judgment as to whether it means a certain level I.Q., a certin level of awareness, or some other reasonable scale.

  • $\begingroup$ I'm not completely sure we can express the odds on our own behalf, much less generically given no information about your ecosystem. What kind of answer are you lookiing for? A straight percenage? $\endgroup$ Jan 24 '18 at 3:09
  • $\begingroup$ Define exactly what you mean by "sentient". If you mean technological/linguistic, like humans, the information we have suggests about 1 in 2000. Dinosaurs appeared ~200 million years ago, modern humans about 100 thousand. $\endgroup$
    – jamesqf
    Jan 24 '18 at 4:36
  • $\begingroup$ I am unaware that sentience has any particular necessities in terms of brain structure, or a need for opposable digits. $\endgroup$
    – Lee Leon
    Jan 24 '18 at 7:45
  • $\begingroup$ Perhaps one could count how many species on Earth at the present are sentient. Since Humans want to count Humans as sentient, the bar is set quite low, and thus many other species might qualify, including various apes, proboscideans, and cetaceans, possibly totaling up to a hundred in all - and that's just mammals. Thus one might divide the number of multi celled species by the number of possibly sentient ones and get a proportion of possibly sentient species existing on an Earth like planet 600 million years after the first multi celled life appeared. $\endgroup$ Jan 25 '18 at 18:27
  • $\begingroup$ I dont want to know the odds of a sentient creature in an ecosystem. I want to know what obsticals a species could face that would progressively kill off the most non-sentient organisms, and cause a evolution among the species, leading to sentience. $\endgroup$ Jan 26 '18 at 3:08

Self awareness is probably most beneficial for creatures that live with others of their kind, a creature needs to understand theory of mind before it can consider what others think of it and what it thinks of itself, i.e. its identity. Many social animals have the capacity to recognise and interact with others preferentially (including individual humans) and it's only these species that'll exhibit altruistic behaviours, because only they understand the value of making a good impression.

You can't build trust with a snake it simply lacks the capacity to differentiate you from its environment, as far as a snake is concerned you're either prey, a predator or irrelevant. Whether you've been feeding it all its life or its just met you for the first time today is irrelevant, the snake simply cannot recognise you as an individual.


The first condition for sentience is a plentiful source of protein, meat protein is best but not strictly necessary as long as the source is easy to chew or mash between rocks and then eat. Brains require a high level of protein and other nutrients, fruit and leaves won't do it, and potato's, yams and sweet potatoes are hard to chew without proper preparation. Meat can be allowed to rot a little, can be softened by hitting it against rocks, or by lightly roasting it on a fire for a few minutes, and is high in protein, making it the ideal food. Large plentiful bugs could fill in for animal meat, as they're also high in protein.

Opposable digits are harder, as they're more of a lucky fluke and many animals can do plenty of things with their paws. The best bet would be having the creature living in an ecosystem where they need to either climb trees, work around thick underbrush, roots or thorns, or have them climbing lots of rocky terrain where they also need to move rocks to get food. Each of these ecosystems would make having more hand dexterity and being able to wrap a hand around something to move it out of the way, pull themselves up, and grab food would encourage an opposable thumb or finger.


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