and a panspermia update, with link in comments to a sweet little pdf
“And how was it that these sophisticated life processes emerged not all that long (in astronomical or geological terms) after Earth cooled enough to be habitable? “Either life developed here super-fast or it came full-on as DNA life from afar,” Ruvkun said.”
and a new paper in Nature on some new archeans, had a great takeaway that may def help the panspermia argument, as the little buggers seem to be primed to move up the chain in anerobic enviros.
“We found that Asgard archaea share many genes uniquely with eukaryotes, including several genes that are involved in the formation of structures that give eukaryotic cells their complex character. Such genes had thus far only been found in eukaryotes, indicating that these archaea were somehow primed to become complex.
I am continually confused as to why people find seven hundred million years (4.4 to 3.7 billion years ago, the date at which we have both the oldest intact rocks on earth and not coincidentally the oldest good evidence for living things) an insufficient time to develop biochemical complexity. The Hadean is more unknown (due to no solid rocks surviving from that era due to geological reprocessing) than hellish, at least to a microbe over evolutionary time. There was liquid water and hydrothermal systems, there was basalt, there was more granitic rock, there was an atmosphere, and equilibrium temperatures were almost certainly not exactly extreme. The late heavy bombardment would NOT have touched the subsurface biosphere, there should be continuity of livable environments for that whole time, and could’ve actually increased the number of interesting hydrothermal environments that chemosynthetic bacteria love overall. Major biochemical inventions and evolutionary transitions can indeed happen remarkably fast, especially when there is no competition to constrain you to a particular ecological niche or established players crowding out newcomers to a process. The genetic code itself shows evidence of an extremely rapid period of evolution with many divergent lineages, of which only one survives in a runaway winner-take-all fashion (more on this in a later post on the nature of LUCA). I see no need to invoke panspermia especially when you have the deep domain split between the bacteria and archaea on Earth, which might be a relic of some deep differences between lineages that invented some important stuff separately.
This being said, GOD YES I want sequencers on other planets in case there is life there with a common biochemistry. Spread of microbes from world to world is not an impossible thing within our solar system. I would highly HIGHLY doubt it between star systems.
The Asgardian archaea are indeed fascinating. They somewhat overstate the case that there are major eukaryotic components in these guys a bit (a lot of the domains are separate rather than strung together the way they are in eukaryotes). There are so many eukaryogenesis models that are consistent with these guys existing though that a lot more research is needed. An alternative hypothesis to them being ‘primed to be complex’ is that they are abortive linages that peeled away from the eukaryogenesis pathway that lead to us and underwent reductive evolution back towards a standard archaean niche. Things can simplify too over evolutionary time.
Great article here on the latest deep bio, tho i can’t read original..
Many Worlds, Subterranean Edition
http://www.manyworlds.space/index.php/2015/11/24/many-worlds-subterranean-edition/
and a panspermia update, with link in comments to a sweet little pdf
“And how was it that these sophisticated life processes emerged not all that long (in astronomical or geological terms) after Earth cooled enough to be habitable? “Either life developed here super-fast or it came full-on as DNA life from afar,” Ruvkun said.”
http://www.manyworlds.space/index.php/2017/01/05/in-search-of-panspermia/
and a new paper in Nature on some new archeans, had a great takeaway that may def help the panspermia argument, as the little buggers seem to be primed to move up the chain in anerobic enviros.
“We found that Asgard archaea share many genes uniquely with eukaryotes, including several genes that are involved in the formation of structures that give eukaryotic cells their complex character. Such genes had thus far only been found in eukaryotes, indicating that these archaea were somehow primed to become complex.
http://astrobiology.com/2017/01/how-complex-cellular-life-may-have-emerged.html
I am continually confused as to why people find seven hundred million years (4.4 to 3.7 billion years ago, the date at which we have both the oldest intact rocks on earth and not coincidentally the oldest good evidence for living things) an insufficient time to develop biochemical complexity. The Hadean is more unknown (due to no solid rocks surviving from that era due to geological reprocessing) than hellish, at least to a microbe over evolutionary time. There was liquid water and hydrothermal systems, there was basalt, there was more granitic rock, there was an atmosphere, and equilibrium temperatures were almost certainly not exactly extreme. The late heavy bombardment would NOT have touched the subsurface biosphere, there should be continuity of livable environments for that whole time, and could’ve actually increased the number of interesting hydrothermal environments that chemosynthetic bacteria love overall. Major biochemical inventions and evolutionary transitions can indeed happen remarkably fast, especially when there is no competition to constrain you to a particular ecological niche or established players crowding out newcomers to a process. The genetic code itself shows evidence of an extremely rapid period of evolution with many divergent lineages, of which only one survives in a runaway winner-take-all fashion (more on this in a later post on the nature of LUCA). I see no need to invoke panspermia especially when you have the deep domain split between the bacteria and archaea on Earth, which might be a relic of some deep differences between lineages that invented some important stuff separately.
This being said, GOD YES I want sequencers on other planets in case there is life there with a common biochemistry. Spread of microbes from world to world is not an impossible thing within our solar system. I would highly HIGHLY doubt it between star systems.
The Asgardian archaea are indeed fascinating. They somewhat overstate the case that there are major eukaryotic components in these guys a bit (a lot of the domains are separate rather than strung together the way they are in eukaryotes). There are so many eukaryogenesis models that are consistent with these guys existing though that a lot more research is needed. An alternative hypothesis to them being ‘primed to be complex’ is that they are abortive linages that peeled away from the eukaryogenesis pathway that lead to us and underwent reductive evolution back towards a standard archaean niche. Things can simplify too over evolutionary time.