In particular, the jump from unicellular to multicellular life is (was) one of the top leading candidates for the Great Filter. https://en.wikipedia.org/wiki/Great_Filter
Importantly, it was one of the filter candidates "behind" us. It will be exciting to see if other potential filter steps can be so conclusively eliminated over time.
A good demo video: https://www.youtube.com/watch?v=amjuJJwI3iM
On a planet with twice the Earth's mass, it would take a larger-than-Saturn-sized rocket to put a Mercury-sized payload into orbit.
EDIT: And said Mercury-sized payload would have to spend more of its mass on heat shielding than the human Mercury capsule if it's intended to come back down.
Mercury was a small space capsule containing 1 person designed to last a few hours in space. The Saturn V rocket was until recently the most powerful rocket ever launched, and took 3 crew, a crew module, a lander module, and payloads, to the moon.
There's just so many unknowns.
Some people consider cooking a critical step in our evolution (cooking enables harvesting more calories from food).
With no good fuel available cooking could also be ... off the menu.
If not grass, dried escrements are also good fuel. People use them in areas of this world with little or no trees.
https://www.newscientist.com/article/mg21028184-300-lab-yeas...
That being said I’m not too shocked. The transition from unicellular to multicellular has always seemed like less of a hurdle to me compared to the start of unicellular life itself.
It took "only" < 400 million years for life to develop, meaning unicellular life, but it took 3 billion years for multicellular life to develop. If we apply this basic rule, multicellular life seems the hard thing. Of course though, statistics wise this is pretty crappy ground to stand on because we only have one sample :).
Edit: [1] From https://en.wikipedia.org/wiki/Multicellular_organism#Occurre...
> Multicellularity has evolved independently at least 46 times in eukaryotes, and also in some prokaryotes, [...] . However, complex multicellular organisms evolved only in six eukaryotic groups [...]
If this statement is true then it is incredibly unlikely life forms in our universe at our current stage exist. Low odds can occur and the only reason anyone is here to observe them is because they did occur. Since we only know of life forming once we cannot make assumptions about the odds of it happening.
Yes, that's what people assume, but the universe existed for billions of years before that, so what if life might have used all that time to evolve before it landed on Earth deep inside some rocks?
The jump from prokaryotic to eukaryotic is far more intimidating.
"Diatom-derived plastids" blew my mind.
- "Metallicity": We probably need a recent / "Population I" star, i.e. it' s probably unlikely that there can be civilizations much older than us (in astronomical dimensions): https://en.wikipedia.org/wiki/Stellar_population#Population_...
- In 1.1 billion years from now, the Sun will be 10% brighter than it is today, and this increase in luminosity will also mean an increase in heat energy, which Earth’s atmosphere will absorb. This will trigger a moist greenhouse effect here on Earth that is similar to the runaway warming that turned Venus into the hellish environment we see there today. So we have appeared only after 80% of the "usable" life span of our star has already been over -- a window that might be easy to miss (an larger stars burn even faster)