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Archaea: The 'Dark Matter' of the Microbial World

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Re: Archaea: The 'Dark Matter' of the Microbial World

#11

Post by evilduck »

jlarocco wrote: post #4
jessriedel wrote: post #3

Is it known why there are no evolutionary intermediates between archea and eubacteria? Nick Lane's book The Vital Questions has been highly recommended by the HN commentariat, and I think it more or less deserves its esteem. Lane gives an extensive theoretical analysis of the sequence of events wherein a eubacterium was engulfed by an archea, and the resulting endosymbiosis that was the beginning of complex (eukaryot…

That's something I've always wondered about evolution in general. Why isn't there a continuum of species? For example, why are there chimpanzees and humans walking around as discrete species with nothing "in between". Seems unlikely that a few chimpanzees gave birth to human babies (or I guess some ancient human ancestor) one day, and then we just branched off and evolved separately leaving the rest of the chimpanzee…

The first and only reason there's no transitionary species between humans and chimpanzees is that we simply are not descendants from them, instead we share a common ancestor with the apes (which was probably more chimp-like if you want to envision what it was). We both evolved from the common ancestor because we fit different environments better. Eventually we developed sufficient intelligence, stemming from some environmental pressure chimps did not have, to manage survival in almost any environment, leading to us leaving them "behind".

From our common ancestor, there is a lot of continuum of hominids in the fossil record however. At some point humans and neanderthals did coexist as a spectrum of hominids coexisting at the same time, and we did "feed back" the most-fit DNA by interbreeding with them until we bred them out of existence.

Re: Archaea: The 'Dark Matter' of the Microbial World

#12

Post by jballanc »

jlarocco wrote: post #4
jessriedel wrote: post #3

Is it known why there are no evolutionary intermediates between archea and eubacteria? Nick Lane's book The Vital Questions has been highly recommended by the HN commentariat, and I think it more or less deserves its esteem. Lane gives an extensive theoretical analysis of the sequence of events wherein a eubacterium was engulfed by an archea, and the resulting endosymbiosis that was the beginning of complex (eukaryot…

That's something I've always wondered about evolution in general. Why isn't there a continuum of species? For example, why are there chimpanzees and humans walking around as discrete species with nothing "in between". Seems unlikely that a few chimpanzees gave birth to human babies (or I guess some ancient human ancestor) one day, and then we just branched off and evolved separately leaving the rest of the chimpanzee…

The terms you want to look up are "allopatric speciation" and "sympatric speciation". In short, events can occur that segment population, and from that point forward you have two species. Given enough time, these two will continue to diverge and split, until you have two completely separate subtrees. It just so happens (or is very likely) that the split between archaea and eubacteria is the earliest of these splits.

Re: Archaea: The 'Dark Matter' of the Microbial World

#13

Post by duncan_bayne »

jlarocco wrote: post #4
jessriedel wrote: post #3

Is it known why there are no evolutionary intermediates between archea and eubacteria? Nick Lane's book The Vital Questions has been highly recommended by the HN commentariat, and I think it more or less deserves its esteem. Lane gives an extensive theoretical analysis of the sequence of events wherein a eubacterium was engulfed by an archea, and the resulting endosymbiosis that was the beginning of complex (eukaryot…

That's something I've always wondered about evolution in general. Why isn't there a continuum of species? For example, why are there chimpanzees and humans walking around as discrete species with nothing "in between". Seems unlikely that a few chimpanzees gave birth to human babies (or I guess some ancient human ancestor) one day, and then we just branched off and evolved separately leaving the rest of the chimpanzee…

There are. Look up "ring species" where the intermediates are geographically separated, rather than chronologically.

Re: Archaea: The 'Dark Matter' of the Microbial World

#14

Post by VLM »

jlarocco wrote: post #4
jessriedel wrote: post #3

Is it known why there are no evolutionary intermediates between archea and eubacteria? Nick Lane's book The Vital Questions has been highly recommended by the HN commentariat, and I think it more or less deserves its esteem. Lane gives an extensive theoretical analysis of the sequence of events wherein a eubacterium was engulfed by an archea, and the resulting endosymbiosis that was the beginning of complex (eukaryot…

That's something I've always wondered about evolution in general. Why isn't there a continuum of species? For example, why are there chimpanzees and humans walking around as discrete species with nothing "in between". Seems unlikely that a few chimpanzees gave birth to human babies (or I guess some ancient human ancestor) one day, and then we just branched off and evolved separately leaving the rest of the chimpanzee…

Its an excellent question for an automotive analogy and if you accept that market pressure evolves cars similar to the process of biological evolution, then its interesting to contemplate various "family tree of car ancestors" while cars evolve into distinct and interesting niches, while at the same time there are no or very few chimera cars on the roads today that are an intermediate form between manufacturers and successful models.

Its actually very unusual in the car world, and I guess in evolution in general, for something like the SUV crossover to evolve where its basically SUV appearance on a car chassis, more or less. I think the closest biological analogy to a crossover SUV is a platypus. Although SUVs aren't nearly as cool as a platypus.

Re: Archaea: The 'Dark Matter' of the Microbial World

#15

Post by rukittenme »

duncan_bayne wrote: post #13
jlarocco wrote: post #4

Earlier quoted context omitted.

That's something I've always wondered about evolution in general. Why isn't there a continuum of species? For example, why are there chimpanzees and humans walking around as discrete species with nothing "in between". Seems unlikely that a few chimpanzees gave birth to human babies (or I guess some ancient human ancestor) one day, and then we just branched off and evolved separately leaving the rest of the chimpanzee…

There are. Look up "ring species" where the intermediates are geographically separated, rather than chronologically.

I second this. Ring species are the easiest way to get into an "evolutionary mindset". They help describe the "grayness" of evolution.

Re: Archaea: The 'Dark Matter' of the Microbial World

#16

Post by munificent »

jlarocco wrote: post #4
jessriedel wrote: post #3

Is it known why there are no evolutionary intermediates between archea and eubacteria? Nick Lane's book The Vital Questions has been highly recommended by the HN commentariat, and I think it more or less deserves its esteem. Lane gives an extensive theoretical analysis of the sequence of events wherein a eubacterium was engulfed by an archea, and the resulting endosymbiosis that was the beginning of complex (eukaryot…

That's something I've always wondered about evolution in general. Why isn't there a continuum of species? For example, why are there chimpanzees and humans walking around as discrete species with nothing "in between". Seems unlikely that a few chimpanzees gave birth to human babies (or I guess some ancient human ancestor) one day, and then we just branched off and evolved separately leaving the rest of the chimpanzee…

> Why isn't there a continuum of species?

In many cases there are. The Burke Museum in Seattle currently has a display about the Pacific Northwest. In one part, they have a row of birds arranged based on where they were found on the Cascade Mountains. You can see them smoothly blend from one kind of coloration to another.

In cases where there are more distinct species, it's because the groups of animals don't interbreed for any of many reasons and then have drifted apart from each other.

Re: Archaea: The 'Dark Matter' of the Microbial World

#17

Post by [deleted] »

jessriedel wrote: post #3

Is it known why there are no evolutionary intermediates between archea and eubacteria? Nick Lane's book The Vital Questions has been highly recommended by the HN commentariat, and I think it more or less deserves its esteem. Lane gives an extensive theoretical analysis of the sequence of events wherein a eubacterium was engulfed by an archea, and the resulting endosymbiosis that was the beginning of complex (eukaryot…

[deleted]

Re: Archaea: The 'Dark Matter' of the Microbial World

#18

Post by rectangletangle »

jlarocco wrote: post #4
jessriedel wrote: post #3

Is it known why there are no evolutionary intermediates between archea and eubacteria? Nick Lane's book The Vital Questions has been highly recommended by the HN commentariat, and I think it more or less deserves its esteem. Lane gives an extensive theoretical analysis of the sequence of events wherein a eubacterium was engulfed by an archea, and the resulting endosymbiosis that was the beginning of complex (eukaryot…

That's something I've always wondered about evolution in general. Why isn't there a continuum of species? For example, why are there chimpanzees and humans walking around as discrete species with nothing "in between". Seems unlikely that a few chimpanzees gave birth to human babies (or I guess some ancient human ancestor) one day, and then we just branched off and evolved separately leaving the rest of the chimpanzee…

Basically if two species occupy the same ecological niche in the same physical location, one will ultimately win out, because it will be slightly more fit. This creates a pressure to either quickly branch into a new and different species, or remain the same. This also taps into the species problem, because the whole concept of a "species" is an artificial human construct, for which nature has no respect.

https://en.wikipedia.org/wiki/Competitive_exclusion_principl...

https://en.wikipedia.org/wiki/Species_problem

Re: Archaea: The 'Dark Matter' of the Microbial World

#19

Post by obastani »

mmustapic wrote: post #10
jlarocco wrote: post #4

Earlier quoted context omitted.

That's something I've always wondered about evolution in general. Why isn't there a continuum of species? For example, why are there chimpanzees and humans walking around as discrete species with nothing "in between". Seems unlikely that a few chimpanzees gave birth to human babies (or I guess some ancient human ancestor) one day, and then we just branched off and evolved separately leaving the rest of the chimpanzee…

It didn't happen like that. Humans didn't branch from chimpanzees or the other way around. At some point there was a common ancestor of both species. Its offsprings diverged into two species that continued evolving into the current humans and chimpanzees.

This doesn't really answer the question -- how come there are usually only a few clearly defined species that descended from this common ancestor? Why isn't there a spectrum?

I don't know anything about the phylogenetic tree of humans and our cousins, but I assume that at some point there was a spectrum (e.g., Neanderthals), but at some point the others got wiped out, without humans splitting any further. Perhaps this is due to the global mobility of humans? What do biologists think?

Re: Archaea: The 'Dark Matter' of the Microbial World

#20

Post by jessriedel »

dekhn wrote: post #5
jessriedel wrote: post #3

Is it known why there are no evolutionary intermediates between archea and eubacteria? Nick Lane's book The Vital Questions has been highly recommended by the HN commentariat, and I think it more or less deserves its esteem. Lane gives an extensive theoretical analysis of the sequence of events wherein a eubacterium was engulfed by an archea, and the resulting endosymbiosis that was the beginning of complex (eukaryot…

Lane has a good story and tells it nicely, but I don't think he represents the mainstream, and he conveniently throws all the evidence that doesn't agree with him under the rug.

Thanks. I did get that impression. Is even the basic eubacteria-inside-archea claim is disputed?
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