If there had been no lunar tides on Earth, would life have been less likely or evolved less? If tides benefited life, how so?

The anthropic principle resolves the rarity of Earth's features that are conducive to intelligent life, including position in the solar system, position in the galaxy, abundance of water, active geology, etc. Might tides be another unusual feature with strong benefits for life? Certainly it seems a rare feature; within the solar system, Earth's moon has 1% of its mass, compared with 0.02% for Saturn and Jupiter, or 0.000002% for Mars.

If there are significant benefits, it might be useful to measure tides on exoplanets, or implement tides as part of terraforming.

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    $\begingroup$ This is an awfully broad topic, could you please edit your question to narrow its scope down a bit? Off the top of my head, some of the wide-ranging effects of tides are tidal friction producing tidal bulging and shaping the landscape, stabilizing planet's atmosphere and climate from what we more commonly refer to as atmospheric tides, tidal friction helping keep the layers of planet's core molten to produce magnetic field, keep oceans liquid, produce local energy gradients and distributing nutrients to primitive lifeforms (say prokaryotes), have a role in tectonic plate movement,... $\endgroup$
    – TildalWave
    Feb 28 '14 at 23:17
  • $\begingroup$ Thanks for your five suggestions, @TidalWave. However I believe only the fourth describes any benefit to life at play on earth. (1) You haven't indicated how the shape of the landscape benefits life. (2) "The largest amplitude atmospheric tides are generated by the periodic heating of the atmosphere by the Sun." $\endgroup$
    – Bob Stein
    Feb 28 '14 at 23:49
  • $\begingroup$ (continuing response to @TidalWave) (3) "...the vast majority of the heat in Earth's interior—up to 90 percent—is fueled by the decaying of radioactive isotopes". (4) Nutrient movement - good contribution! (5) Tectonic plate motion is "powered by forces originating in Earth's radioactive, solid iron inner core". So, maybe this question is 20% as broad as you thought, off the top of your head? $\endgroup$
    – Bob Stein
    Feb 28 '14 at 23:50
  • $\begingroup$ There are some links in my comments I'd like you to read, @TidalWave. They're not very visible here are they. Please feel free to support specific connections between tides and land masses, biodiversity, weather, the geomagnetic field, thermal budgets, etc., with references. The nutrient rearrangement is good, I might upvote that in an answer, however I'm not sure there's any support for the carbon cycle being significantly less active if there were no lunar tides. But I'll try to have an open mind. I think you could write a great answer if you researched it carefully. $\endgroup$
    – Bob Stein
    Mar 1 '14 at 0:19
  • $\begingroup$ @TidalWave, another thought, if you believe strongly that lunar tides are important and inseparable from conditions conducive to life on Earth, then that makes this question all the more relevant: we should search for tides on exoplanets as a clue to life, or worthiness to colonize, and we should consider manufacturing tides somehow in terraforming. In that case I urge you to list the benefits in an answer with brief explanations and good references. My brief research turned up several contradictions to the benefits you've come up with so far. But I hope you'll press on. $\endgroup$
    – Bob Stein
    Mar 1 '14 at 0:54

100% of all planets on which evolution of intelligent life has been observed have unusually strong tides. But considering the sample size (one), it is quite a stretch to assume a causal link.

According to the theory of evolution, a trait evolves when this trait increases the chance of having off-springs which in turn also have off-springs which pass this trait on. That means an environment in which intelligence evolves needs to provide some kind of challenge which can be overcome through applying intelligence and which, when overcome, provides a better chance of having off-springs. Tides result in an ecosystem along the coastlines which is constantly changing and might provide such a challenging environment.

But it would be quite a stretch to assume that it is the only possible way how the intelligence of any lifeforms could be challenged in a way which makes it beneficial for them to be more intelligent. Some cephalopods, for example, are considered to be quite intelligent even though they evolved in the sea where tidal effects don't have much effect on their environment (octopuses seem to be capable of communication, learning, simple tool use and... sport betting :) ).

But that is all just theoretical navel-gazing. To find out if there is a correlation between tides and intelligent life or not, we need more examples of planets with intelligent or at least non-intelligent life.

  • $\begingroup$ Yep. Extrapolating from a sample size of one is always a bit of a risky undertaking. $\endgroup$ Mar 1 '14 at 22:43

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