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Toba catastrophe theory





yagnyavalkya
The Toba catastrophe theory says that there may have been a bottleneck in human evolution due to the eruption that occurred at Lake Toba (Sumatra, Indonesia)
You comments on this
Mrs Lycos
I would comment if there was more information to be based on. Is there some sort of site where this theory is further discussed and explained? Or at least would you care to elaborate a bit more? Who stated this theory? Without more elements, you assume everybody is well versed in this theory, something I don't think many are...
yagnyavalkya
Mrs Lycos wrote:
I would comment if there was more information to be based on. Is there some sort of site where this theory is further discussed and explained? Or at least would you care to elaborate a bit more? Who stated this theory? Without more elements, you assume everybody is well versed in this theory, something I don't think many are...

Take a look here
http://en.wikipedia.org/wiki/Toba_catastrophe_theory
Bikerman
It seems plausible but perhaps redundant (insofar as current research seems to show that the entire human population was around 26,000 as far back as 1.2 million years ago - no bottleneck indicated)
http://www.pnas.org/content/early/2010/01/06/0909000107.full.pdf+html
kelseymh
yagnyavalkya wrote:
The Toba catastrophe theory says that there may have been a bottleneck in human evolution due to the eruption that occurred at Lake Toba (Sumatra, Indonesia)
You comments on this


Why don't you express your own opinion? Tell us what you think, and engage in a discussion.

Or are you supposed to be writing a paper for a class, and trying to get others to do your work for you?
yagnyavalkya
kelseymh wrote:
yagnyavalkya wrote:
The Toba catastrophe theory says that there may have been a bottleneck in human evolution due to the eruption that occurred at Lake Toba (Sumatra, Indonesia)
You comments on this


Why don't you express your own opinion? Tell us what you think, and engage in a discussion.

Or are you supposed to be writing a paper for a class, and trying to get others to do your work for you?


I will my opinion in my next post
I am not writing a paper and not getting to get others work for me I am sorry if you are offended
yagnyavalkya
kelseymh wrote:


Why don't you express your own opinion? Tell us what you think, and engage in a discussion.


The Toba Catastrophe was an event some 70-75,000 years ago when a Sumatran volcano erupted, creating a dust envelope over a large part of the globe, this kind of thing could have caused volcanic winter mainly by preventing sun light to reach ground According to Ambrose, Stanley H. in his paper entitled "Late Pleistocene Human Population Bottlenecks, Volcanic Winter, and Differentiation of Modern Humans." Journal of Human Evolution 34 (6) (1998): 623–651.this kind of thing could have reduced the human population drastically and would have hindered evolution. This is more analyzed with a genetic perspective, in context of rate of mutations and observable genetic diversity in humans and this suggests a small population 70,000 years ago. I feel that not only human population but also all forms of terrestrial life would have been affected. One can say that the Toba Catastrophe is hypothetical, and the evidence surrounding it too thin to sustain much in the way of conclusions. The event has been studies and there is evidence for this (http://dx.doi.org/10.1038%2F276574a0 ). There are papers which say that hominin survived the changed climatic environments these papers (one of them is http://dx.doi.org/10.1016/j.quaint.2011.07.042 ) study the Toba event “Primary air-fall deposits of the Young Toba Tuff (YTT) study the changes in terrestrial environments prior to and after the super-eruption.” So the event must have occurred.
The paper Bikreman has cited does show that entire human population was around 26,000 as far back as 1.2 million years ago but it does not say anything about what would have been the population 70,000 years ago and if this toba event happened how much it would have reduced to and how hominin continued to propagate and evolve. The journal “Quaternary International” has a lot of papers on this topic.
truespeed
How would it have hindered evolution? A dramatic event like that could of helped us evolve in as much as it would of forced us to be more resourceful to survive,you could argue without it maybe we wouldn't of evolved to where we are now at all.
yagnyavalkya
truespeed wrote:
How would it have hindered evolution? A dramatic event like that could of helped us evolve in as much as it would of forced us to be more resourceful to survive,you could argue without it maybe we wouldn't of evolved to where we are now at all.

reduction in genetic diversity lose of variability
The phenomenon called genetic drift is context here
small isolated populations can have special circumstances that induce rapid changes in gene frequencies and this may not be connected to mutation and natural selection.
http://anthro.palomar.edu/synthetic/synth_5.htm
truespeed
Maybe only those with a specific genetic make up survived and the disaster resulted in a clearing out of the deadwood genes,and those that were left not being hampered or held back by the ones who couldn't survive,were then able to progress.

I don't really know what i am saying,something along the lines of that maybe diversity isn't always good,and the narrowing down of the gene pool through an event that ensured that the only survivors were the most resourceful of the species meant that only those resourceful genes were passed on which then sped up our progress.
Hello_World
I don't think there is any special trait that could help people with strong genes survive a volcano eruption.

I think that deadwood theory may be useful if you are talking about some kind of plague etc. rather than an indiscriminate form of natural disaster.

Decreasing genetic diversity is certainly a negative if the reduction is not related to a 'survival of the fittest' type of reduction.

An extreme example is the Tasmanian Devil, who was close to hunted to extinction, before recovering. However, it was so close that Tasmanian Devil have almost no diversity. Due to this, they have a dreadful cancer which is passed contagiously and thus far have found no individuals who can withstand it. Their only real hope is to remove some Devils from the wild and raise them away from the natural habitat.

eg http://sydney.edu.au/vetscience/Foundation/help/devil.shtml
or http://www.philly.com/philly/blogs/evolution/Cancer-genetics-and-the-Tasmanian-devil.html
yagnyavalkya
Hello_World wrote:
I don't think there is any special trait that could help people with strong genes survive a volcano eruption.

I think that deadwood theory may be useful if you are talking about some kind of plague etc. rather than an indiscriminate form of natural disaster.

Decreasing genetic diversity is certainly a negative if the reduction is not related to a 'survival of the fittest' type of reduction.

An extreme example is the Tasmanian Devil, who was close to hunted to extinction, before recovering. However, it was so close that Tasmanian Devil have almost no diversity. Due to this, they have a dreadful cancer which is passed contagiously and thus far have found no individuals who can withstand it. Their only real hope is to remove some Devils from the wild and raise them away from the natural habitat.

Maybe not then
but now if some people has the technology to predict these events
Bikerman
yagnyavalkya wrote:
kelseymh wrote:


Why don't you express your own opinion? Tell us what you think, and engage in a discussion.


The Toba Catastrophe was an event some 70-75,000 years ago when a Sumatran volcano erupted, creating a dust envelope over a large part of the globe,

I must take issue with this, for the sake of clarity and accuracy.

It is my understanding that the Toba Supererruption is the event referred to above.
The Toba Catastrophe refers to the theory that the Toba Supererruption caused a severe bottleneck in human population (as low as 1-10 thousand globally) because of the 10 yr volcanic winter and subsequent cooling episode that resulted from the Toba Supererruption.
yagnyavalkya
Bikerman wrote:
yagnyavalkya wrote:
kelseymh wrote:


Why don't you express your own opinion? Tell us what you think, and engage in a discussion.


The Toba Catastrophe was an event some 70-75,000 years ago when a Sumatran volcano erupted, creating a dust envelope over a large part of the globe,

I must take issue with this, for the sake of clarity and accuracy.

It is my understanding that the Toba Supereruption is the event referred to above.
The Toba Catastrophe refers to the theory that the Toba Supereruption caused a severe bottleneck in human population (as low as 1-10 thousand globally) because of the 10 yr volcanic winter and subsequent cooling episode that resulted from the Toba Supereruption.

OK but in general a catastrophe is an extremely large-scale disaster and the supereruption was that
Toba catastrophe "theory" referes to the bottleneck but the Toba catastrophe is the supereruption
I said "The Toba Catastrophe was an event some 70-75,000 years ago when a Sumatran volcano erupted, creating a dust envelope over a large part of the globe, and not The Toba Catastrophe "theory" was an event some 70-75,000 years ago when a Sumatran volcano erupted, creating a dust envelope over a large part of the globe
The Toba Catastrophe need not only refer to the theory it can refer to the supereruption too
Bikerman
We are not talking 'in general' - the science forum should be tighter than that.
In scientific parlance, catastrophe refers to a dinscontinuous change in some natural phenomenon or another, usually severely affecting one or more biological systems and/or populations. The field of study concerning such catastrophe is called 'catastrophe theory' - being based on the work on Pointcare, Zeeman et al.

The theory that the Toba super-eruption caused a catastrophe is the Toba Catastrophe theory. The fact of the eruption is not in serious question. Whether or not it caused a catastrophe IS in serious question.
Example

Thus I think it is best to stick to :
Toba (super)eruption - the event itself (massive volcanic eruption).
Toba Catastrophe theory - the theory that the Toba supereruption caused a catastrophic decline in human population.
yagnyavalkya
Bikerman wrote:

In scientific parlance, catastrophe refers to a dinscontinuous change in some natural phenomenon or another, usually severely affecting one or more biological systems and/or populations.

Can you quote a reference for this definition "in scientific parlance" I mean who has defined this
yagnyavalkya
Bikerman wrote:
Whether or not it caused a catastrophe IS in serious question.
Example


The article does not discuss evolution it talks about survival of the species
The Toba catastrophe theory is about a bottleneck in human evolution
Bikerman
I wasn't attempting a definition - merely a broad description.
If a definition is required then I would concede that a 'catastrophe' in geological terms can mean simply a sudden disturbance/change in the surface of the earth, BUT I would also point out that the modern use of catastrophe in geology often has a different meaning - neo-catastrophism being the
Quote:
explanation of sudden extinctions in the palaeontological record by high magnitude, low frequency events, as opposed to the more prevalent geomorphological thought which emphasises low magnitude, high frequency events.

Wiki

I'm simply trying to avoid confusion. A quick search of the literature reveals the specific words 'Toba Catastrophe' only occur very infrequently UNLESS followed immediately by the word 'theory'.

I'm only suggesting - if you want to talk about the toba catastrophe then fine, but I think that is would be perverse to use a general term where a more specific and informative one is more ubiquitously used and available (ie (super)eruption vs catastrophe).
yagnyavalkya
Bikerman wrote:
I wasn't attempting a definition - merely a broad description.
If a definition is required then I would concede that a 'catastrophe' in geological terms can mean simply a sudden disturbance/change in the surface of the earth, BUT I would also point out that the modern use of catastrophe in geology often has a different meaning - neo-catastrophism being the
Quote:
explanation of sudden extinctions in the palaeontological record by high magnitude, low frequency events, as opposed to the more prevalent geomorphological thought which emphasises low magnitude, high frequency events.

Wiki

I'm simply trying to avoid confusion. A quick search of the literature reveals the specific words 'Toba Catastrophe' only occur very infrequently UNLESS followed immediately by the word 'theory'.

I'm only suggesting - if you want to talk about the toba catastrophe then fine, but I think that is would be perverse to use a general term where a more specific and informative one is more ubiquitously used and available (ie (super)eruption vs catastrophe).

Fine thanks for clearing it
yagnyavalkya
In my opinion
There are a lot of articles on the supererruption and also on the catastrophe
I feel that plant life also could have had an impact by the supereruption and it possible that
Plants could have adapted to different environmental conditions caused by the toba event and this could have changed the course of evolution
particularly in the context of gases present in the atmosphere after the supereruption
Bikerman
OK, points arising:
a) Atmospheric gases post-event.
http://www.sciencedirect.com/science/article/pii/S0277379101001548

b) Effect on atmosphere
http://www.sciencemag.org/content/317/5834/114.full
http://www.sciencedirect.com/science/article/pii/S1040618211001911

c) Effects of ash/sediment
http://www.sciencedirect.com/science/article/pii/S0033589409001355
http://www.sciencedirect.com/science/article/pii/S104061821100440X

d) Possible effects on evolution/species distribution
http://books.google.co.uk/books?hl=en&lr=&id=9CRV7JDhW0sC&oi=fnd&pg=PA71&dq=Toba+supereruption+effect+evolution&ots=_iwqGR-Y1t&sig=HTcZ_yTxDXF5f92RWEMfGfcmsx4#v=onepage&q=Toba%20supereruption%20effect%20evolution&f=false
http://www.sciencedirect.com/science/article/pii/S0047248498902196

Opinion? I tend to the opinion that the effects have been somewhat overstated, though obviously there would have been SOME effects from such a large event.
I am extremely dubious concerning the 'change evolution' hypothesis. I cannot see how the event would have formed sufficient separated/isolated breeding communities of plants (or, come to that, of animals) to speed-up or otherwise radically alter evolution. Of course it could have introduced several new 'niches' in local/regional biospheres, and would have changed the regional and, perhaps, global environment sufficient to cause at least a possible slight change in some selection mechanisms, but I don't see how it would have had a major widespread effect on plant evolution - unless a proposed mechanism can be pointed to.....
yagnyavalkya
Bikerman wrote:
I cannot see how the event would have formed sufficient separated/isolated breeding communities of plants (or, come to that, of animals) to speed-up or otherwise radically alter evolution.

Maybe slow down but not radically alter evolution
This can be known only when we have control situations
or how the plants would have evolved had there not been the supereruption in the same geographical area
yagnyavalkya
Bikerman wrote:

a) Atmospheric gases post-event.
http://www.sciencedirect.com/science/article/pii/S0277379101001548

b) Effect on atmosphere
http://www.sciencemag.org/content/317/5834/114.full
http://www.sciencedirect.com/science/article/pii/S1040618211001911

c) Effects of ash/sediment
http://www.sciencedirect.com/science/article/pii/S0033589409001355
http://www.sciencedirect.com/science/article/pii/S104061821100440X

d) Possible effects on evolution/species distribution
http://books.google.co.uk/books?hl=en&lr=&id=9CRV7JDhW0sC&oi=fnd&pg=PA71&dq=Toba+supereruption+effect+evolution&ots=_iwqGR-Y1t&sig=HTcZ_yTxDXF5f92RWEMfGfcmsx4#v=onepage&q=Toba%20supereruption%20effect%20evolution&f=false
http://www.sciencedirect.com/science/article/pii/S0047248498902196


Good papers
Any literature specifically on effect on plants
yagnyavalkya
Bikerman wrote:
I tend to the opinion that the effects have been somewhat overstated, though obviously there would have been SOME effects from such a large event.
I am extremely dubious concerning the 'change evolution' hypothesis. I cannot see how the event would have formed sufficient separated/isolated breeding communities of plants (or, come to that, of animals) to speed-up or otherwise radically alter evolution. Of course it could have introduced several new 'niches' in local/regional biospheres, and would have changed the regional and, perhaps, global environment sufficient to cause at least a possible slight change in some selection mechanisms, but I don't see how it would have had a major widespread effect on plant evolution - unless a proposed mechanism can be pointed to.....

Here is one plants and changes in forests
http://www.sciencedirect.com/science/article/pii/S0031018209004271
The article says that "Our results demonstrate that the Toba eruption caused climatic cooling and prolonged deforestation in South Asia, and challenge claims of minimal impact on tropical ecosystems and human populations"
Bikerman
Yes, but even given such change I still don't see what evidence there is for a change in plant evolution. This is only 70k years ago and the geological/archaeological/palaeontological record is surely pretty large, and genetics can help with some gaps....It should be possible (and I'm sure it has been done) to trace back the genetic branching points for the main families of flora AND fauna - this would show any sudden evolutionary spurt or exctinction event - which we don't eeem to observe.
yagnyavalkya
Bikerman wrote:
Yes, but even given such change I still don't see what evidence there is for a change in plant evolution. This is only 70k years ago and the geological/archaeological/palaeontological record is surely pretty large, and genetics can help with some gaps....It should be possible (and I'm sure it has been done) to trace back the genetic branching points for the main families of flora AND fauna - this would show any sudden evolutionary spurt or exctinction event - which we don't eeem to observe.

70 K years ago is early enough
the interesting part is the change in biodiversity observed or inferred or detected
C4 trees which don't have CO2 concentrating mechanism was replaced by grasses which have efficient CO2 concentration mechanisms maybe the changes in concentration of CO2 in the atmosphere after the supererruption had something to do with it
truespeed
Hello_World wrote:
I don't think there is any special trait that could help people with strong genes survive a volcano eruption.

I think that deadwood theory may be useful if you are talking about some kind of plague etc. rather than an indiscriminate form of natural disaster.

Decreasing genetic diversity is certainly a negative if the reduction is not related to a 'survival of the fittest' type of reduction.

An extreme example is the Tasmanian Devil, who was close to hunted to extinction, before recovering. However, it was so close that Tasmanian Devil have almost no diversity. Due to this, they have a dreadful cancer which is passed contagiously and thus far have found no individuals who can withstand it. Their only real hope is to remove some Devils from the wild and raise them away from the natural habitat.

eg http://sydney.edu.au/vetscience/Foundation/help/devil.shtml
or http://www.philly.com/philly/blogs/evolution/Cancer-genetics-and-the-Tasmanian-devil.html


The Tasmanian Devil was confined to a very small area,whereas the human population at the time however small would of been spread right across the globe presumably,so the genetic differences would of still been quite diverse.

Also that wasn't a natural disaster that required a survival of the fittest element,whereas the above scenario would indicate that only those with the survival instincts and the ability to cope and prosper in extreme circumstances would of survived,hence the theory of a ridding of the genetic deadwood and the resulting prominence of the cunning elite. Smile
Ankhanu
yagnyavalkya wrote:
Bikerman wrote:
Yes, but even given such change I still don't see what evidence there is for a change in plant evolution. This is only 70k years ago and the geological/archaeological/palaeontological record is surely pretty large, and genetics can help with some gaps....It should be possible (and I'm sure it has been done) to trace back the genetic branching points for the main families of flora AND fauna - this would show any sudden evolutionary spurt or exctinction event - which we don't eeem to observe.

70 K years ago is early enough
the interesting part is the change in biodiversity observed or inferred or detected
C4 trees which don't have CO2 concentrating mechanism was replaced by grasses which have efficient CO2 concentration mechanisms maybe the changes in concentration of CO2 in the atmosphere after the supererruption had something to do with it

That would work better if the timing were right. The C4 grasses really took off 7-8 million years ago, spreading relatively rapidly from their origins (Cerling et al. 1997)... this is well before the 70,000 years of the Toba eruption. I can't comment on measured CO2 levels after the eruption, as I haven't really looked into the information yet, but IIRC, CO2 levels would likely have increased, which may have limited the competitive advantage of C4 over C3 photosynthesizers. That aside, carbon sequestering wouldn't really explain the C4 grass systems without other factors, such as fire and/or heavy herbivory or other strong perturbation (Bond, 2008).

I'm not going to really jump into this topic for a little bit yet, as I want to read up on the topic first. I've largely ignored human evolution topics, but it could be fun to explore genetic drift potential here.

Bond WJ. 2008. What limits trees in C4 grasslands and savannas? Annual Review of Ecology, Evolution and Systematics 39: 641-659

Cerling TE, Harris JM, MacFadden BJ, Leakey MG, Quade J, et al. 1997. Global vegetation change through the Miocene/Pliocene boundary. Nature 389:153–58
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