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One good example is that as far as we can tell multi-cellular life only evolved on Earth once. And while life started up on Earth pretty quickly it took about 6

by neaden 10y ago

One good example is that as far as we can tell multi-cellular life only evolved on Earth once. And while life started up on Earth pretty quickly it took about 600 million years for that life to become multicelluar. It's possible that we'll someday discover life is relatively common but never meet anything but amoebas.

cmrdporcupine 10y ago
Totally. Not only did multicellular life only evolve once, but eukaryotes themselves seem to have evolved only once. And they are 1000x more complex than their prokaryote predecessors. [edit: without any real evidence of anything convincingly between prokaryote and eukaryote] It's one thing to say there might have been abiogenesis elsewhere that created something like the simple self-reproducing energy machines that bacteria and archaea are. It's another to claim that there is some inevitable progression from that to complex multicellular life. In my opinion this is a very teleological, very 'progressivist' notion of evolution that implies that one inevitably follows from another, and it is not borne out in the reality of what we know so far about happened on earth and what follows from first principles. There may be a lot of complex, self-reproducing systems in the universe. It's arrogant to assume that any of them have to look anything like what we call "life" unless by life we mean the simplest single cell organisms. [edit: In fact it looks like simple prokaryotes evolved _twice_ on earth a "short" distance in time apart].
- Retric 10y ago
  Multi cellular life has evolved several times. There are several distinct cases of single called organisms promoting conditions which aid others of it's species. Causing a colony to form, and then spawn new colonies. Now, highly complex multicellular life seems to share common descent. But that likely has more to do with predation than anything else. Further single called organisms preform horizontal gene transfer to both other single called life and multicellular life, making things impossible to trace back.
Retric 10y ago
That's not really known. Of note life showed up very close to as soon as possible on early earth. So, similar events may have happend 30+ times. However, the first time life shows up it can spread easily, the second time it's likely food.

by neaden 10y ago

cmrdporcupine 10y ago

Totally. Not only did multicellular life only evolve once, but eukaryotes themselves seem to have evolved only once. And they are 1000x more complex than their prokaryote predecessors. [edit: without any real evidence of anything convincingly between prokaryote and eukaryote] It's one thing to say there might have been abiogenesis elsewhere that created something like the simple self-reproducing energy machines that bacteria and archaea are. It's another to claim that there is some inevitable progression from that to complex multicellular life. In my opinion this is a very teleological, very 'progressivist' notion of evolution that implies that one inevitably follows from another, and it is not borne out in the reality of what we know so far about happened on earth and what follows from first principles. There may be a lot of complex, self-reproducing systems in the universe. It's arrogant to assume that any of them have to look anything like what we call "life" unless by life we mean the simplest single cell organisms. [edit: In fact it looks like simple prokaryotes evolved _twice_ on earth a "short" distance in time apart].

Retric 10y ago
Multi cellular life has evolved several times. There are several distinct cases of single called organisms promoting conditions which aid others of it's species. Causing a colony to form, and then spawn new colonies. Now, highly complex multicellular life seems to share common descent. But that likely has more to do with predation than anything else. Further single called organisms preform horizontal gene transfer to both other single called life and multicellular life, making things impossible to trace back.

Retric 10y ago

That's not really known. Of note life showed up very close to as soon as possible on early earth. So, similar events may have happend 30+ times. However, the first time life shows up it can spread easily, the second time it's likely food.