Great filters
There must be at least one great filter preventing life from spreading to other planet.
https://www.astronomy.com/science/the-great-filter-a-possible-solution-to-the-fermi-paradox/
The fact that life emerged very early on earth does indicate that the emergence of life is not a great filter, this however does not provte it since it could be the case that the conditions early on earth was what allowed life to emerge and that if life hadn't emerged then it would become very unlikely for it to emerge later. More research on this is needed.
Large, multicellular life forms may have appeared on Earth one billion years earlier than was previously thought. Macroscopic multicellular life had been dated to around 600 million years ago, but new fossils suggest that centimetres-long multicellular organisms existed as early as 1.56 billion years ago.
https://www.nature.com/articles/533441b
- The right star system (including organics and potentially habitable planets)
- Reproductive molecules (e.g. RNA)
- Simple (prokaryotic) single-cell life
- Complex (eukaryotic) single-cell life
- Sexual reproduction
- Multi-cell life
- Tool-using animals with intelligence
- A civilization advancing toward the potential for a colonization explosion (where we are now)
- Colonization explosion
If that finding is correct it would not be too long after the emergence of sex. Sex does accelerate evolution and without it earth would have become uninhabitable before intelligent life could evolve.
The emergence of multicellular life itself however can not be a great filter since it has happened at least 30 times already.
Multicellularity has evolved independently at least 25 times in
eukaryotes,
[7][8] and also in some
prokaryotes, like
cyanobacteria,
myxobacteria,
actinomycetes,
Magnetoglobus multicellularis or
Methanosarcina.
[3] However, complex multicellular organisms evolved only in six eukaryotic groups:
animals,
symbiomycotan fungi,
brown algae,
red algae,
green algae, and
land plants.
The emergence of life capable of building an advanced civilization in the first place could maybe be a great filter. High intelligence is often not actually selected for. Sure humans are currently very successful as an animal but that that took a long time and required unlikely scenarios to happen.
Sea animals like orcas can probably never build any real civilization regardless of intelligence, they don't have hands.
Most land animals also lack hands so even if they would somehow evolve high enough intelligence they still couldn't use it effectively (which is part of the reason why it doesn't evolve in the first place).
But that is all behind us so it's likely that those are not the biggest hurdles.
Nuclear war probably is not anywhere close to some great filter since it's very much surviveable, one issue however is that those wars can be very destructive setting civilizations back significantly.
