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Our biology teacher told us that among worse conditions one of the reason that intelligent life had actually evolved on land is that there is a more important selective pressure due to the bigger number of predators.

Is there really relatively fewer predators (in numbers) on the land? What is the cause of this phenomenon?

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closed as primarily opinion-based by Remi.b, AliceD, WYSIWYG Jan 9 '17 at 6:03

Many good questions generate some degree of opinion based on expert experience, but answers to this question will tend to be almost entirely based on opinions, rather than facts, references, or specific expertise. If this question can be reworded to fit the rules in the help center, please edit the question.

  • $\begingroup$ I wouldn't say that conditions are poorer on land, but it's definitely more diverse (as you say). But I'm not sure that this is the cause, as I think many of the fish species are predators to other fish species or marine organisms and microorganisms. And although I don't agree with the term "intelligent life", we do have marine organisms, such as dolphins, for which we give anthropocentrically intelligent characteristics. $\endgroup$ – BioGeo Jan 3 '17 at 12:40
  • $\begingroup$ Check this out. It won't answer your question on the predators, but maybe give some more ideas and opinions on the matter of intelligent life (just found it looking after I saw your question): pbs.org/wgbh/evolution/humans/intlife/index.html?fy $\endgroup$ – BioGeo Jan 3 '17 at 12:50
  • $\begingroup$ @BioGeo Thanks but I actually argued that marine is more diverse (I imagined harsh conditions such as a desert or polar areas :) but you're right, maybe I can imagine better that there are lot more diverse climates due to the changing climate on the land $\endgroup$ – Probably Jan 3 '17 at 13:46
  • $\begingroup$ Is the question "Are the more predators on land? (In (relative?) number of species or in (relative?) number of individuals?)" or is it "Why are there more predators on land?". If the question is the second one, then a citation is needed but I guess you are rather asking the first (on of the first actually) question. $\endgroup$ – Remi.b Jan 4 '17 at 18:06
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I wouldn't say conditions on land are poorer... just more unstable, less predictable over a span of a million years. And an unstable environment appears to be one of the factors in the evolution of human intelligence. ie the environment changes faster than evolution can adapt the body... so one solution is to adapt the animal's behavior which requires intelligence.

That said, dolphins too are plenty intelligent. Octopus also are quite good puzzle solvers.. but are short lived.

As for predator -prey ratio https://www.mcgill.ca/newsroom/channels/news/why-arent-there-more-lions-254873 Here is something to read. Predator-prey ratio appear to be govern by the rate of growth of prey items

And prey in the ocean has a faster turn around in the ocean.. so there are more predators in the ocean than on land. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4240998/.

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    $\begingroup$ Sorry, I think you haven't answered the question (I'm sorry for bad formulation) if there is bigger predator-prey ratio on land. $\endgroup$ – Probably Jan 3 '17 at 14:29
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    $\begingroup$ The ratio of predator to prey is higher in the ocean than it is on land. So the predator prey ratio is not the cause for intelligence. $\endgroup$ – JayCkat Jan 4 '17 at 5:07

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