NAWKI October 2017 - Life with no moon

30 Nov 2017

NAWKI (life, but Not As We Know It), is a monthly series exploring the hypotheticals of real and artificial life


Emily Dolson: The question for October is “How would life be different if there were no moon?”

Tim Atkinson: I dug out a New Scientist article I read like 14 years ago which seemed relevant.

I must have been 10 and my mum started me on NS early haha

Seems pretty influential

Iñaki Fernández Pérez: Without having read that article, here is my small contribution to the question: no moon means 1) no sea and ocean tides, 2) asteroids that collided with the moon would have collided with the earth instead, 3) the regulation process that the moon exerts on the orbit of the earth would not exist

I guess that we should clarify if the question refers to: 1) the moon never existed, or 2) the moon suddenly disappears once life already developed

both seem interesting

d9w: Thanks for the article, @Tim Atkinson. If I can summarize: the strong tides from the early moon could have provided a good environment for DNA formation due to high variability in coastal salinity. High tide meant low salinity and breaking double-stranded molecules, low tide meant higher salinity and more molecular formation, and this cycle could have led to molecular strands like DNA forming

Without opening the entire early Earth chemistry issue, though, I wouldn’t take this to mean that no moon = no life. There have been a number of ways proposed for RNA formation that could do without tidal forces

Not to mention panspermia (although I think we should mention panspermia :P)

The effect of tidal forces on life formation is definitely worth considering though. In the event that DNA or even RNA did come around, I would imagine that a lack of tidal forces on coastlines would make life gathering in those places much less rare, slowing down aquatic evolution

Tim Atkinson: Ay, I’m not suggesting that definitely no moon = no life, just that its a possible extreme interpretation of there being no moon

d9w: Yup. I definitely think no moon = harder life

Tim Atkinson: I can’t find a source but I also remember somewhere claiming that tides were important for the development of land based life

aquatic life in tidal regions can be exposed to the air for a few hours before being submerged again which allows an incremental development

but again, I can’t find the source or offer more detail

d9w: @Iñaki Fernández Pérez, I’d say the question is “without a moon at X point.” So even if the moon is necessary for early molecular mixing, what if there were no moon once life got started?

also i’ll point out that when we’re discussing tides, the sun has a slight tidal effect that we shouldn’t ignore.

Tim Atkinson: yeah if you take it to mean “the moon never existed”, and if you buy into the giant impact hypothesis then no moon, no collision between early Earth and “Theia”, so the Earth’s outer layers never vaporised and we’re pretty much in a different timeline at that point

good point :simple_smile:

Emily Dolson: This is making me realize that I know surprisingly little about the role of intertidal creatures in the transition to living on land. That argument completely makes sense - it would set up a nice evolutionary gradient where progressively more resistance to being out of the water was always advantageous. But I feel like everything I’ve ever learned about the transition to land is about the fin-limb transition. And Tiktaalik doesn’t exactly seem like a tide-pool creature.

The hypothesis I’ve heard about Tiktaalik is that it lived mostly in shallow water, but its limb-like fins allowed it to occasionally venture out on land. So I guess that sort of uses behavior to create the same evolutionary gradient (i.e. any additional ability to survive out of the water is selectively advantageous) that tides might. Which would be an argument that we could still have life without the moon.

Is this the article you were thinking of, @Tim Atkinson?

Oh, oops, look at me and my tetrapod-centric worldview. Arthropods were the first animals on land. But the same argument about behavior applies.

d9w: Agreed on the evolutionary gradient based on strong tides. The transition to land seems like one of the big emergent changes in evolutionary history (type-2 novelty in Banzhaf et al. “Defining and simulating open-ended novelty: requirements, guidelines, and challenges.” terms, I think)

Having tides would mean a greater chance for land exposure without developing any behavior that gets you on land; the water would do that alone. Similarly to how DNA formation could have profited from “[throwing] water up on a hot rock, then have the waters recede and evaporate,” certain organisms might have displayed exaptation once they were also thrown up on some hot rocks

I didn’t realize this until today, but this question is very seasonal for Halloween :simple_smile: That would certainly be different if there were no moon

Seems like intertidal areas were certainly important for bacterial migration to land, which makes sense.

The author here mentions estuaries, though, and that’s a good point: there are some places where water is going to move up and down coastlines without tides. So, again, for this part of evolution, it seems like the moon helped quite a bit by making tides, but it wasn’t the only means for a transition to land.

I’d like to ask about non-tidal impact of the moon, though. @Iñaki Fernández Pérez brought up more asteroids and the changes to the earth’s orbit. I’ll posit that a lot of life has used moonlight for sensing. Would the eye have evolved as many times as it did if nights were always dark? Would we see more bio-luminescence?

Emily Dolson: Oh, yeah, good point about bacteria. I was trying to think about early mosses, but was similarly having a hard time figuring out if they actually first evolved in places where there were tides, vs. in rivers.

I feel like I should know the answer to this, but without the moon how dark would the night be? For instance, without human-generated light, can cats see anything during new moon? I would assume they can, but now I’m doubting myself.

Or were you more thinking of sensing in terms of the way moths use the moon to determine which way is up?

I guess a very minor side effect of having no moon is that we wouldn’t have to deal with moths flying into our lights and dieing :simple_smile:. Of course, that’s predicated on us still existing and having lights.

pennyfaulkner: I’m interested in the impact of the moon on human development and time. An hour is a division of the day into 12 or 24 blocks depending on how you measure, this is a number we don’t generally see used as a divisor otherwise though. However high tide changes by about an hour a day. Months and weeks can both be traced back to origins based on lunar calendars. How would we measure time without the moon? With out a strong and reliable way to measure time at several levels can civilization progress as far as it has?

For reference even plankton react to lunar cycles to define rhythmic behaviours.

Emily Dolson: That’s a really interesting point. Without a moon, it would be possible to perceive daily cycles and yearly cycles, but not monthly cycles. I wonder if we’d see calendars that used seasons in place of months?

d9w: according to the giant impact theory, the Earth’s axial tilt is a result of the Moon’s formation, so we might not have had seasons either. But if our solar system is any indicator for the general case, axial tilts seem pretty variable, so I think we could count on a hypothetical no-Moon Earth to have some seasons.

I’ve also seen that 12 was a common divisor because of its number of factors, so early economic systems favored it, hence dozens and grosses. Hours don’t seem to apply there, though, at least in modern perception; people don’t think about 6 hours as a unit like a half-dozen.

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