Oxford scientists say: Looks like no other intelligent life in whole universe (but keep looking)

[RJM Corbet]

I'm sure I've read recently that this has happened multiple times throughout the history of life, so far as we understand it - I'll keep an eye out for the reference. We have both chloroplasts and mitochondria as capture events for starters.

Also, I'm increasing getting the impression that speciation among microorganisms is very much a forced issue of categorization - that they spend so much time sharing genes that we may not be able to tell the difference between one single individual being captured by symbiosis or entire different populations, especially if the captured microorganism lose genes over time that would otherwise differentiate them. In other words, there is never a "single capture event" but instead many events over time of a shared set of genes from different populations, and that speciation among prokaryotes is a very fluid concept.

In fact, I think we profoundly misunderstand the history of life - that the story of early life is effectively about the evolution of a soup of proteins, into a soup of RNA, then a soup of DNA. It's only when we get into the hyper-specialization of advanced eukaryotes that it becomes less obvious, but even then the issue of gene transfer is still an active mechanism. I think the problem may be simply because humans are so used to defining the world in terms of hyper-specialized of advanced eukaryotes that our frame of references fails to account to less specialized and more basic prokaryotes, and our bias ends up blinding us.

What puzzles me at the moment is how the host cell replicates the captured one in more advanced eukaryotes, because so far as I understand it the captured one certainly isn't replicating with its own DNA - that instead, the host cell is replicating it using its own DNA, as if the host cell were nothing more than an organelle. For example, I don't believe seeds contain chloroplasts in their cells, so the cells in seeds have to build them, along with the chloroplast DNA. I really need to research this properly, though.

"Symbiogenesis (endosymbiotic theory, or serial endosymbiotic theory) is the leading evolutionary theory of the origin of eukaryotic cells from prokaryotic organisms. The theory holds that mitochondria, plastids such as chloroplasts, and possibly other organelles of eukaryotic cells are descended from formerly free-living prokaryotes (more closely related to the Bacteria than to the Archaea) taken one inside the other in endosymbiosis ..."
(Article from Wiki and most of it way over my head, I'm afraid)

My earlier comments are taken from Nick Lane Professor of Evolutionary Biochemistry at the University College of London

 

[RJM Corbet]

Another article from Wiki, more specific to the topic:

"Eukaryogenesis the process which created the eukaryotic cell and lineage, is a milestone in the evolution of life, since eukaryotes include all complex cells and almost all multicellular organisms. The process is widely agreed to have involved symbiogenesis, in which archaea and bacteria came together to create the first eukaryotic common ancestor (FECA) ...

Biologists have proposed multiple scenarios for the creation of the eukaryotes. While there is broad agreement that the LECA must have had a nucleus, mitochondria, and internal membranes, the order in which these were acquired has been disputed. In the syntrophic model, the first eukaryotic common ancestor (FECA, around 2.2 gya) gained mitochondria, then membranes, then a nucleus. In the phagotrophic model, it gained a nucleus, then membranes, then mitochondria.

In a more complex process, it gained all three in short order, then other capabilities. Other models have been proposed. Whatever happened, many lineages must have been created, but the LECA either out-competed or came together with the other lineages to form a single point of origin for the eukaryotes. Nick Lane and William Martin have argued that mitochondria came first, on the grounds that energy had been the limiting factor on the size of the prokaryotic cell ..."

etc

 

[Vertigo]

I'm sure I've read recently that this has happened multiple times throughout the history of life, so far as we understand it - I'll keep an eye out for the reference. We have both chloroplasts and mitochondria as capture events for starters.

Also, I'm increasing getting the impression that speciation among microorganisms is very much a forced issue of categorization - that they spend so much time sharing genes that we may not be able to tell the difference between one single individual being captured by symbiosis or entire different populations, especially if the captured microorganism lose genes over time that would otherwise differentiate them. In other words, there is never a "single capture event" but instead many events over time of a shared set of genes from different populations, and that speciation among prokaryotes is a very fluid concept.

In fact, I think we profoundly misunderstand the history of life - that the story of early life is effectively about the evolution of a soup of proteins, into a soup of RNA, then a soup of DNA. It's only when we get into the hyper-specialization of advanced eukaryotes that it becomes less obvious, but even then the issue of gene transfer is still an active mechanism. I think the problem may be simply because humans are so used to defining the world in terms of hyper-specialized of advanced eukaryotes that our frame of references fails to account to less specialized and more basic prokaryotes, and our bias ends up blinding us.

What puzzles me at the moment is how the host cell replicates the captured one in more advanced eukaryotes, because so far as I understand it the captured one certainly isn't replicating with its own DNA - that instead, the host cell is replicating it using its own DNA, as if the host cell were nothing more than an organelle. For example, I don't believe seeds contain chloroplasts in their cells, so the cells in seeds have to build them, along with the chloroplast DNA. I really need to research this properly, though.




To me it's the other way around - that we have such a strong cultural bias into thinking humans and the place we live is so special that believing life could only exist on Earth is the greater act of Faith. After all, life on Earth seems to be following a perfectly normal set of physical laws, that to argue life doesn't exist elsewhere in the universe would be effectively stating that the same laws of physics don't exist elsewhere in the universe!

You misunderstand me. I have never said I believe Earth is the only place with life. I neither believe that nor that there is other life. Both would be, to me, acts of faith. There is no evidence for either proposition and until there is both of those positions remain, to me pure speculation not science. I may hope for the latter but without evidence it can be no more than that.

Also with the soup of DNA theory that would, I'm sure, predict very large variations in DNS amongst life on Earth and yet all life on earth shares the majority of their DNA which to me is the strongest argument for abiogenesis and a single event. The captured 'cell' is not really a cell within a cell it was the merging of the two strands of life to form the eukaryote and that too only appears to have happened the once.

 

[Vertigo]

Scientists have families to feed and lives to live. It would be interesting to know how many of them have devoted their lives to finding ET, and how just want a well paid job. If you can combine the two then great, but I suspect that most would prioritise the latter over the former.

In relation to the speed of light and the distance between planets, stars and galaxies. It's impractical for the two to co-exist; like having an empty motorway with a 2 mph speed restriction in place. What's the point in having so a wide, expansive universe if you can only ever stare up at it?

Which (without any kind of scientific reasoning) gives me hope that there is some way to get from A to B faster; we just have to find out what it is. And once we do, everything will change.

That rather presupposes that there is any point to the universe in the first place. Personally I think not; it just is. Which sort of makes all life a kind of parasite really

 

[Toby Frost]

To me, there is evidence that life evolving to intelligence has low likelihood. Dinosaurs were on the Earth for about 170 million years without any development of intelligence. This seems to indicate non-intelligent life can be a very stable pattern.

The dinosaurs were definitely getting cleverer, and might well have got very clever indeed. However, given their biology, they might well not have evolved the sort of intelligence that we have. I could see ants coming up with a very strange sort of intelligence. (Warhammer's Tyranids were interesting, as they were all parts of a sophisticated and self-aware hive, but as individuals didn't seem to be very bright at all, although Warhammer introduced some psychic stuff to explain how they functioned.)

Given mankind's capacity for wars, genocides and reality-denying cults, I suspect that intelligence may not be very useful for an organism's survival, especially if some kind of contentment is involved in that.

 

[Brian G Turner]

You misunderstand me. I have never said I believe Earth is the only place with life. I neither believe that nor that there is other life. Both would be, to me, acts of faith.

Oh, my apologies if it came across as a personal accusation - I meant as in an unconscious bias we humans still carry around with us. After all, across the space sciences most people have had no objection to accepting the existence of things we cannot see, but the moment anyone touches on the subject of life, we require absolutely proof of existence. Why can we easily accept the existence of an Oort Cloud surrounding our solar system, which cannot be seen or even inferred, but we can't accept that the existence of life - as demonstrated by basic biochemistry - should be a natural part of the laws of physics? If life exists only on Earth, doesn't that mean biochemistry is only capable of happening here? Just a rhetorical question.

Also with the soup of DNA theory that would, I'm sure, predict very large variations in DNS amongst life on Earth and yet all life on earth shares the majority of their DNA which to me is the strongest argument for abiogenesis and a single event.

If we're progressing from a RNA World scenario, then there would be a massive amount of shared DNA already in place. What I'm suggesting is that at present a top-down approach is being taken, where we define our approach to life and genetics in terms of speciation we see at the advanced eukaryote level - which means everything has to follow from a single cell from a single unique species - but if we take a bottom-up approach, we find a lot more fluidity which means no single event is required, and that multiple events would be the norm. That's why we see so much endosymbiosis among microorganisms.

Anyway, just thinking aloud.

 

[RJM Corbet]

If life exists only on Earth, doesn't that mean biochemistry is only capable of happening here? Just a rhetorical question.

Brian I think the argument is not about the existence of life on other worlds, but about intelligent life -- considering the fine-tuning coincidences? The 'quantum jump' from prokaryote to eukaryote isn't lightly dismissed as virtually inevitable?

I suspect that intelligence may not be very useful for an organism's survival,

Ah -- it sure helped Mowgli, lol?

 

[Stephen Palmer]

Intelligence is evolution by natural selection's answer to environmental change occurring too fast for genetics to cope with, eg humanoids in Africa around 5-3 million years ago. I think it is useful, but there are consequences when coupled with consciousness.

 

[Vertigo]

Intelligence is evolution by natural selection's answer to environmental change occurring too fast for genetics to cope with, eg humanoids in Africa around 5-3 million years ago. I think it is useful, but there are consequences when coupled with consciousness.

I think that's a slightly glib statement, if you'll pardon my saying so. Were that the case then far more animals should have developed intelligence. 'Humanoids' were by no means the only animals at the time subject to environmental change. I would be more inclined to argue that it evolved out of extreme curiosity from an omnivore that was prepared to try anything to eat and survive, and who had also developed excellent manipulators through an arboreal existence.

 

[Stephen Palmer]

Yes, I suppose it's pretty general, fair enough. I think it was very much true for human progenitors though. Also their fantastic colour vision. The term "intelligence" has in some quarters become a bit of a catch-all...

 

[Christine Wheelwright]

To me, there is evidence that life evolving to intelligence has low likelihood. Dinosaurs were on the Earth for about 170 million years without any development of intelligence. This seems to indicate non-intelligent life can be a very stable pattern. It took some very precise conditions to reset the dominant life forms and create conditions for a more intelligent animal branch to arise. lt is only mammals that moved beyond the intelligence of crows.

I'm not so sure. I think if you combine rudimentary intelligence with the ability to manipulate the environment (say opposable thumbs) and the power of evolution across time, then you have everything you need for the development of a highly intelligent species. I think most of the major hurdles come earlier (that initial moment at which life is somehow created).

On the subject of probabilities, I don't think we have enough information to assess them. If we could fully understand the mechanism by which rudimentary life first formed (even replicate it in a lab) then we might be in a position to evaluate the odds of this happening elsewhere in the Universe based on planetary characteristics, time scales etc.

 

[Ursa major]

parts of a sophisticated and self-aware hive

See also Vernor Vinge's A Fire Upon the Deep for something vaguely similar.