Still every little bit counts. If the moon was much larger it would actually have a negative effect on the development of life. The tidal forces of the moon were probably more significant though in getting sea life to move onto land. The most important factor here isn't the actual size of the moon but the proportional difference relative to the earth, which is the closest to a double planet, outside of Pluto (which is no longer considered a planet anyway.) If we want to talk about absolute size, Jupiter was probably the best shield, especially because it actually used to be closer to the sun in the primordial solar system and migrated to its current position later on.Not really, see last part of post here. Right now the Moon blocks 0.0005% of asteroids that would hit Earth. Even in the very distant past when it was much closer to Earth, the most it could block was still much less than 1%.
People often underestimate how small and far away the Moon is. It is not a good shield. It has a lot of craters on it, but we don't see all the impacts that Earth had since geologic processes have erased most of them.
About my point on intelligence, I would like to expand on that. Based on my conversations with biologists who actually work with these animals, we do a huge disservice when we dont recognize their intelligence. They even argue with me when I mention that higher animals have the intelligence of a 5 year old child and tell me that dolphins, elephants, bonobos, chimps, gorillas, grey parrots, etc., have intelligence and emotions and empathy that parallels our own. It's just expressed differently- like a different language. They are magnificent examples of parallel evolution, which the dinosaurs of the later Cretaceous also experienced. People who dont give credit to animals for their intelligence are speciests and are a major reason why animals have been mistreated and abused (even by some scientists during experimentation.) We can also extrapolate this to theorize that in the universe there can be types of difference vastly different from our own, that dont require a large centralized brain. An example of this is the ant, they have large complex social structures, even keep aphids as pets, and have large nurseries. There are even signs of intelligence at the unicellular level (amoebas) and many socalled artificial human structures mimic what the slime mold is able to do. Not only that, but according to some, like Fred Hoyle, we can envision intelligence that doesn't even require a planet for propagation (hive intelligence in the form of interstellar dust or even pure energy.) My reason for thinking that technological civilizations are very rare is not because human beings are somehow rare and special (this is the mistake made by people who fall for the Anthropic Principle- same reason why I think there are infinite universes), it's because technology and industry are destructive to the species that develops it. We can see this with humanity quite easily.....I felt this way 30 years ago and everything I've seen in those 30 years shows me I was right. Industrial farming techniques have depleted nutrients from the soil and damaged the environment (as India and Africa are now finding out), nasty pollution and overpopulation of humans has resulted in the sixth mass extinction in the planet's history, and average human's ignorance of these issues makes me doubt the actual intelligence of humans. Human nature itself (greed rather than being cooperative like ants, warlike nature, short term benefits gained by sacrificing long term goals) is self destructive and it's the height of arrogance and ignorance for people to consider themselves to be somehow specially intelligent....I even find the so-called "scientific name" of homo sapiens "man the wise"? to be a ridiculous and mockworthy title.
Getting back to my original point, if we use the Kardashev Scale, which indicates how much energy a species is able to harness, humanity falls below the entry point of what I would consider advanced. Humanity is only a 0.7 based on that objective scale, and my minimum value for what I'd consider advanced is 1.0. Most technological species probably go extinct or devolve into a lower level of society before they ever reach Level 1 (which is what I think humanity's ultimate fate will be) and the number that I think would actually reach Level 1 is probably in the single digits, and likely the lower single digits. I admit that the Kardashev Scale is also in some ways anthropic, but since we only have a sample size of 1, that's all we have to work with right now. One of the reasons I like the Kardashev scale is because it makes predictions that can be verified as we move along the scale.....very similar to Isaac Asimov's psychohistory. It's actually a nice mathematical framework for that conjecture.....and the turbulent times it predicts as we approach Level 1 were predicted by it. I think that will only increase and will be the first of the truly Great Filters (and one that I dont believe we will be able to cross, mainly because humanity is the ultimate procrastinator and when ever more rapid responses are required to more rapid changes as we get closer to that level, a higher level of insightfulness and selflessness will be required than humanity possesses. This is where having AI helping run our governments would be a great help- but will humanity have the selflessness to let it guide us to make decisions based purely on science, sustainability and logic (and working with nature rather than against it), and rather than the taint and corruption of money and greed?