3 events that happened only once in history

[MarkE]

- Ribozyme self-replication happened only once in history, and it’s the ancestor of all eukaryotic life on Earth

- Endosymbiosis that lead to eukaryotic cells happened only once in history, and it’s the ancestor of all multicellular life on Earth

- Two ape chromosomes that fused together into one human chromosome (chromosome 2) happened only once in history, and it’s the ancestor of all human life on Earth

 

What is the reason that these events could only have happened once in history, and will never happen again?

Edited January 2, 2018 by MarkE

[studiot]

45 minutes ago, MarkE said:

What is the reason that these events could only have happened once in history, and will never happen again?

 

What evidence do you have that either such events only happened once or that they will (do you mean cannot or will not?) never happen again?

[MarkE]

@studiot Because evolution is an unbroken lineage of genetic transmission. The Y-chromosomal Adam is the most recent common ancestor from whom all currently living humans are descended patrilineally. We're all descended from one man. Mitochondrial Eve is the matrilineal most recent common ancestor of all currently living humans. This has been proven in genetical research.

Whether an event like this won't ever happen again in the future however, I cannot provide any proof. Assuming that it could, then of course my question would by: Why didn't it happen yet? 

But if homo sapiens theoretically could evolve once again, then our notion of what evolution is and how it works has to be revised completely. Therefore it seems unlikely to me for this to even happen again in the future. But I'd like to know for sure of course, that's why I came to this forum with my question.

[studiot]

 

3 minutes ago, MarkE said:

Because evolution is an unbroken lineage of genetic transmission.

 

Stating things without support/evidence doesn't make it so.

Why for instance could your first occurrence not have happened many times over with many blind evolutionary alleys?

Now you seem to have dispensed with the first two and narrowed the issue down to the emergence of humans, so which do you want just humans or all life?

8 minutes ago, MarkE said:

But if homo sapiens theoretically could evolve once again, then our notion of what evolution is and how it works has to be revised completely.

I think that both this and the first quote tries to impute too much from too little information.

You should be aware that we know absolutely nothing about any life on the earlier techtonic configurations of the Earth since all that material has been recycled.

 

[MarkE]

29 minutes ago, studiot said:

Stating things without support/evidence doesn't make it so.

I've just showed you proof from genetic research, didn’t I? Moreover, professor M. Hazen made the same statement about self-replicating ribozymes, I didn't make it up myself.

Occam’s razor suggests that, until proven differently, we ought to stay with the most probable explanation, because the statement with the fewest assumptions should be selected when you have two competing theories. You’re absolutely right to state that we know absolutely nothing about any life on the earlier tectonic configurations of the Earth, but I’m not convinced to accept that these three events could theoretically happen once again, it is therefore equally probable.

So I'm not convinced of the alternative until there is any assumption to suggest that it could happens once again. But I'm always open for any suggestions.

Edited January 2, 2018 by MarkE

[dimreepr]

2 minutes ago, MarkE said:

I've just showed you proof from genetic research, didn’t I?

 

No, you've just decided your right.

4 minutes ago, MarkE said:

Occam’s razor suggests that, until proven differently, we ought to stay with the most probable explanation, because the statement with the fewest assumptions should be selected when you have two competing theories. You’re absolutely right to state that we know absolutely nothing about any life on the earlier tectonic configurations of the Earth, but I’m not convinced to accept that these three events could theoretically happen once again, it is therefore equally probable.

1

How do you know it isn't happening all the time and is eaten by more evolved creatures? But since you bring probability to the table you have to accept that all three have happened here, on earth at least once, one planet among many trillions, it's probably happened many times maybe even here.

[Phi for All]

19 minutes ago, MarkE said:

Occam’s razor suggests that, until proven differently, we ought to stay with the most probable explanation, because the statement with the fewest assumptions should be selected when you have two competing theories.

But aren't you suggesting an extreme explanation, that it only happened once and never again? How is that consistent with OR? The simplest and most observed explanation is that it's happened and failed many times.

And what you have presented is "evidence", not "proof", and it doesn't support your explanation.

[CharonY]

Also, ribozymes are clearly not the ancestor of eurkayotic life but fall into the category of the RNA world hypothesis, which is far from an established fact. More specifically though, how do you define "only once"? There are obviously plenty of ribozymes and their early origins are still unclear. Also chromosome re-arrangement has been observed in many species and is clearly not an unique event either.

Forgot to add, endosymbiotic events related to formation of eukaryotes also happened more than once. Mitochondria likely originated from aerobic bacteria, whereas plastids likely evolved from cyanobacteria.

Edited January 2, 2018 by CharonY

[MarkE]

@CharonY You're absolutely right, the animal lineage (Rickettsiales) as well as the green plant lineage (Cyanobacteria) have had their own endosymbiotic event back in the days. So that makes two, not one. Still, for 3,5 billion years, that's not so much.

23 hours ago, Phi for All said:

The simplest and most observed explanation is that it's happened and failed many times.

But isn't that the same as stating that it didn't happen? As an anology: I can try to score 1000 times, but if the goal keeper manages to stop the ball 999 times, I did NOT score 999 times, right? I failed, 999 times, therefore it didn't happen 999 times, even though I've tried. I'd like to know why it didn't happen, and if it could have happened, what went wrong. 

23 hours ago, dimreepr said:

How do you know it isn't happening all the time and is eaten by more evolved creatures?

I don't know this of course, but I'm wondering why it has never been observed. Why should it happen all the time?

Edited January 3, 2018 by MarkE

[dimreepr]

3 minutes ago, MarkE said:

 

I don't know this of course, but I'm wondering why it has never been observed. Why should it happen all the time?

 

Why not?

[EdEarl]

It could have happened several times, but other linkages died out. 

[MarkE]

24 minutes ago, EdEarl said:

It could have happened several times, but other linkages died out. 

Interesting. Could you please clarify this a bit? I'd like to understand the process.

Edited January 3, 2018 by MarkE

[EdEarl]

Infant mortality was much higher 100,000 years ago than it is today. A modern human could have been born and died prior to the one that survived.

Edited January 3, 2018 by EdEarl

[CharonY]

2 hours ago, MarkE said:

So that makes two, not one. Still, for 3,5 billion years, that's not so much.

If your question is regarding events after the rise of eukaryotes, there are plenty more examples. Prominent examples include e.g. rhizobia or mycorrhiza. There many examples of relatively recent photosynthetic cases of endosymbiosis, especially in protists (Paulinella is an model organism for this), many flagellates have metabolic endosymbionts and so on and so forth.

[MarkE]

17 hours ago, CharonY said:

If your question is regarding events after the rise of eukaryotes, there are plenty more examples. Prominent examples include e.g. rhizobia or mycorrhiza. There many examples of relatively recent photosynthetic cases of endosymbiosis, especially in protists (Paulinella is an model organism for this), many flagellates have metabolic endosymbionts and so on and so forth.

I wasn't talking about endosymbionts in general, even our own human stomach has endosymbionts, rather I was referring to the origin of eukaryotic cells (fungi and protists are also eukaryotes). My question was why a prokaryote never seems to invade/engulf another prokaryote anymore. For instance, only one cyanobacterium lead to the development of all plants. Why only one? Cyanobacteria still exist to this day.

[studiot]

It is interesting to contrast natural evolution with human development as processes that result in a more viable syste.

 

Nature appears to use the scattergun approach.
Try every possible variation and discard the failures (in large quantities).

Human try to be more cunning and only try those variations with the greatest assessed chance of success (and not all of those either).

[Endy0816]

On 1/4/2018 at 5:34 AM, MarkE said:

I wasn't talking about endosymbionts in general, even our own human stomach has endosymbionts, rather I was referring to the origin of eukaryotic cells (fungi and protists are also eukaryotes). My question was why a prokaryote never seems to invade/engulf another prokaryote anymore. For instance, only one cyanobacterium lead to the development of all plants. Why only one? Cyanobacteria still exist to this day.

Probably does on occasion, but finds itself in a highly competitive environment now.

On 1/4/2018 at 7:15 AM, studiot said:

It is interesting to contrast natural evolution with human development as processes that result in a more viable syste.

 

Nature appears to use the scattergun approach.
Try every possible variation and discard the failures (in large quantities).

Human try to be more cunning and only try those variations with the greatest assessed chance of success (and not all of those either).

Apes seeking the low hanging fruit.

[MarkE]

6 hours ago, Endy0816 said:

Probably does on occasion, but finds itself in a highly competitive environment now.

What about two ape chromosomes fusing together to create, once again, just like 7 million years ago, a new/higher hominin lineage? 

Edited January 6, 2018 by MarkE

[Endy0816]

I don't know if apes are tracked, but we see chromosomal abnormalities regularly in our own species.

You would have a similar situation to the earlier one. We're occupying the intelligent species niche. Resources are no longer plentiful and uncontested as they once were.

[MarkE]

On 07/01/2018 at 3:28 AM, Endy0816 said:

I don't know if apes are tracked, but we see chromosomal abnormalities regularly in our own species.

You would have a similar situation to the earlier one. We're occupying the intelligent species niche. Resources are no longer plentiful and uncontested as they once were.

What about the evolution of plants? Not only did chloroplasts develop only once by endosymbiosis of cyanobacteria, but all the flowering plants have an outer ring of male parts with an inner ring of female parts, which supports the idea that the flower arose only once as well.

[Strange]

33 minutes ago, MarkE said:

What about the evolution of plants? Not only did chloroplasts develop only once by endosymbiosis of cyanobacteria, but all the flowering plants have an outer ring of male parts with an inner ring of female parts, which supports the idea that the flower arose only once as well.

There are other possibilities. Both may have occurred more than once, but only descendants of one instance survives.

In the case of the structure of flowers, other possibilities exist. It could be due to flowers evolving multiple times but from a similar underlying structure. Or it could be due to convergent evolution. (I don't know much about the evolution of flowers, but it does seem that all extant flowering plants have a common ancestor. But even that doesn't mean that flowers only evolved once.)

[Endy0816]

1 hour ago, MarkE said:

What about the evolution of plants? Not only did chloroplasts develop only once by endosymbiosis of cyanobacteria, but all the flowering plants have an outer ring of male parts with an inner ring of female parts, which supports the idea that the flower arose only once as well.

This recently came out:

Quote

In a paper published Thursday in the journal PLOS Biology, a couple of scientists proposed an answer to the abominable mystery of why angiosperms replaced gymnosperms so abruptly. Kevin Simonin, an assistant professor of ecology and evolution at San Francisco State University, and Adam Roddy present evidence that it all comes down to the efficiency of cells. The secret to angiosperms’ success, they say, is a rapid downsizing of the plants’ cells beginning about 140 million years ago. This downsizing dramatically increased their efficiency. Once angiosperms became that much more efficient, their domination of terrestrial ecosystems was only a matter of time.

www.inverse.com/article/40088-charles-darwin-abominable-mystery-solved-angiosperms-gymnosperms

 

I'd say generally unless there's a mass die off or isolation the same novelty won't give the same results evolving a second time.

 

To contrast, something like the Saber Tooth trait is a good example of one that evolved multiple times at different points.

https://en.m.wikipedia.org/wiki/Saber-toothed_cat

Edited January 12, 2018 by Endy0816

[Silvestru]

1 hour ago, MarkE said:

What about the evolution of plants? Not only did chloroplasts develop only once by endosymbiosis of cyanobacteria, but all the flowering plants have an outer ring of male parts with an inner ring of female parts, which supports the idea that the flower arose only once as well.

What about the possibility that it happened around the same time in different locations? Like Strange mentioned convergent evolution. Maybe that was the organism adapting as well as it could to it's environment. 

A dolphin is a mammal, a Tuna is a fish and a Besanosaurus was a reptile. They are not closely related yet they all have fins.

Would it make sense for me to declare without a shred of doubt that they all have the same fin carrying ancestor?

 

Spoiler

 

#FinsOnlyHappenedOnce!

[MarkE]

21 hours ago, Silvestru said:

Would it make sense for me to declare without a shred of doubt that they all have the same fin carrying ancestor?

In the book 'Our inner fish' I've read that it's just this one gene (the SHH gene) that is responsible for our limbs, the fins of dolphins, and the fins of fish. So yes, the environment does influence the shape of an organism, but in the end it can be narrowed down to only one gene to rule them all.

[Strange]

On 12/01/2018 at 12:48 PM, MarkE said:

What about the evolution of plants? Not only did chloroplasts develop only once by endosymbiosis of cyanobacteria, but all the flowering plants have an outer ring of male parts with an inner ring of female parts, which supports the idea that the flower arose only once as well.

On the evolution of flowering plants, this might be of interest: http://www.bbc.com/news/science-environment-42656306