I voted for that, but my view is a bit more fine grained. I think complex multicellular life with efficient energy is rare. My view is based on the fact that there was life about as soon as possible on earth but it took billions of years to get mitochondria and large complex multicellular life. Once you got that you had a very rapid explosion and tons of highly complex species within a few hundred million years. And multiple fairly intelligent species within a few hundred million after that. My assumption is the step with the longest gap is the most unlikely piece.
Wait… don’t all eukaryotes have mitochondria, including unicellular ones? I think “Complex single cells unlikely” on the poll is a better fit to your position.
It is worth noting that there are numerous examples of endosymbiosis all over the tree of life and the mitochondrion and plastids aren’t the only ones, just the most successful and most ancient.
There are bacteria that have bacterial endosymbiotes, and I’ve seen electron micrographs of large bacteria with strange uncharacterized archaea hanging off them like tassles. Some animals, mostly insects that drink plant sap, have endosymbiotic bacteria that have had their genomes stripped down to only 150 genes and cannot make their own cellular energy that only exist to make essential amino acids so that the animal does not have to eat them. Large numbers of photosynthetic microbes have taken up eukaryotic green algae as second-order endosymbiotes, or even have taken those organisms up as tertiary endosymbiotes.
EDIT: here’s a chart of the bizarre known history of clades acquiring photosynthesis via known primary, secondary and tertiary endosymbiosis. By the time you are at tertiary endosymbiosis, the plastid has 6 nested membranes and may have some vestigial nuclei between some of them.
It is worth noting that the Cambrian also coincided with the Earth releasing from an ice age that makes everything since look mild, as well as the increase of atmospheric oxygen to levels within an order of magnitude or two of today.
It is also worth noting that there is equivocal evidence of multicellular life before the Cambrian that nobody quite agrees on what it means—things that look like worm-trails in seafloor sediment a billion years old (but that some think could be trails from the motion of giant protists), flat sheets with a distinct center and edge 2 gigayears old, and macroscopic curly fibers two or more gigayears old...
I’m wary of calling cyanobacteria with their specialized nitrogen-fixer cells or the various colonial sporangia-forming bacteria ‘multicellular’. They do some hellacious cell specializing within colonies, and there are other bacteria that form chains between reducing and oxidizing environments with bacteria in the middle passing electrons back and forth so as to allow the whole colony to metabolize things one bacterium couldn’t, but it’s arguably a little different than what we think of when we think of a mushroom or an animal.
Eukaryotes have however evolved unambiguous multicellularity on many occasions.
In lineages not directly discended from one another (though they do have a common (unicellular) ancestor). According to the article I linked to it even happened to prokaryotes, though “complex” multicellular organisms (whatever that means—I guess cells not only bound together but also specialized?) ‘only’ evolved six times among eukaryotes.
It is possible that eukaryotes are particularly propense to becoming multicellular the way the OP claims bilaterians are propense to becoming intelligent, but I’d interpret each item of the poll to be conditional on all of the above, and I’d take “complex single cell life” to mean eukaryotes on Earth or similar.
To whoever voted for “Multi-cell life unlikely”: Multicellularity has evolved independently at least 46 times.
I voted for that, but my view is a bit more fine grained. I think complex multicellular life with efficient energy is rare. My view is based on the fact that there was life about as soon as possible on earth but it took billions of years to get mitochondria and large complex multicellular life. Once you got that you had a very rapid explosion and tons of highly complex species within a few hundred million years. And multiple fairly intelligent species within a few hundred million after that. My assumption is the step with the longest gap is the most unlikely piece.
Wait… don’t all eukaryotes have mitochondria, including unicellular ones? I think “Complex single cells unlikely” on the poll is a better fit to your position.
It is worth noting that there are numerous examples of endosymbiosis all over the tree of life and the mitochondrion and plastids aren’t the only ones, just the most successful and most ancient.
There are bacteria that have bacterial endosymbiotes, and I’ve seen electron micrographs of large bacteria with strange uncharacterized archaea hanging off them like tassles. Some animals, mostly insects that drink plant sap, have endosymbiotic bacteria that have had their genomes stripped down to only 150 genes and cannot make their own cellular energy that only exist to make essential amino acids so that the animal does not have to eat them. Large numbers of photosynthetic microbes have taken up eukaryotic green algae as second-order endosymbiotes, or even have taken those organisms up as tertiary endosymbiotes.
EDIT: here’s a chart of the bizarre known history of clades acquiring photosynthesis via known primary, secondary and tertiary endosymbiosis. By the time you are at tertiary endosymbiosis, the plastid has 6 nested membranes and may have some vestigial nuclei between some of them.
Yeah, somewhat. I think what I was getting at by complex multi cellular life is that I think the cambian explosion http://en.m.wikipedia.org/wiki/Cambrian_explosion is rare.
It is worth noting that the Cambrian also coincided with the Earth releasing from an ice age that makes everything since look mild, as well as the increase of atmospheric oxygen to levels within an order of magnitude or two of today.
It is also worth noting that there is equivocal evidence of multicellular life before the Cambrian that nobody quite agrees on what it means—things that look like worm-trails in seafloor sediment a billion years old (but that some think could be trails from the motion of giant protists), flat sheets with a distinct center and edge 2 gigayears old, and macroscopic curly fibers two or more gigayears old...
Why did it take 0.6 billion years from Eukaryotic cells to simple multi-celled organisms?
Define “independently.”
I’m wary of calling cyanobacteria with their specialized nitrogen-fixer cells or the various colonial sporangia-forming bacteria ‘multicellular’. They do some hellacious cell specializing within colonies, and there are other bacteria that form chains between reducing and oxidizing environments with bacteria in the middle passing electrons back and forth so as to allow the whole colony to metabolize things one bacterium couldn’t, but it’s arguably a little different than what we think of when we think of a mushroom or an animal.
Eukaryotes have however evolved unambiguous multicellularity on many occasions.
In lineages not directly discended from one another (though they do have a common (unicellular) ancestor). According to the article I linked to it even happened to prokaryotes, though “complex” multicellular organisms (whatever that means—I guess cells not only bound together but also specialized?) ‘only’ evolved six times among eukaryotes.
It is possible that eukaryotes are particularly propense to becoming multicellular the way the OP claims bilaterians are propense to becoming intelligent, but I’d interpret each item of the poll to be conditional on all of the above, and I’d take “complex single cell life” to mean eukaryotes on Earth or similar.