Almost all modern species came into being same time

[siti]

Am I mistaken or is their data really showing a loss of mitochondrial diversity within species rather than anything to do with speciation per se? I am not really grokking what is "new" here - and I mean in the actual paper not the silly media (mis)interpretations.

 

[Thermos aquaticus]

I am not really grokking what is "new" here - and I mean in the actual paper not the silly media (mis)interpretations.

I came to the same conclusion. The authors seem to be hinting at a massive worldwide speciation event 100k to 200k years ago, but I don't see how the data can support that. You can get mtDNA MRCA's even without a speciation event in a population with a steady and continuous population, so I don't see how you can use intraspeices mtDNA to reliably detect a speciation event and/or a genetic bottleneck unless it is very recent (i.e. last 25,000 years).

 

[siti]

I came to the same conclusion. The authors seem to be hinting at a massive worldwide speciation event 100k to 200k years ago, but I don't see how the data can support that. You can get mtDNA MRCA's even without a speciation event in a population with a steady and continuous population, so I don't see how you can use intraspeices mtDNA to reliably detect a speciation event and/or a genetic bottleneck unless it is very recent (i.e. last 25,000 years).

I am certainly no geneticist but it seems to me that the data merely confirms a rather trivial genealogical fact - that we are all rather more closely related than we might think - which is simply to say that all the members of a species (at any time) have common ancestry (in this case female) much more recently than we might intuitively imagine. Its not really about speciation at all as far as I can tell, its about heredity. I'm sure I'm missing something here - I guess I'll have to go back and read it more carefully.

 

[beenherebeforeagain]

I think that they are saying, primarily, that the mtDNA method is about as reliable as the other 30 methods that biologists use to identify species.

The other aspect seems to be that there are two (at least) possible explanations, but that neither is currently provable--one explanation being that all species went through a genetic bottleneck...either a single breeding pair, or a population of thousands for thousands of years.

It all hinges on whether or not the bar codes in the mtDNA are neutral or selected for by evolutionary pressure...something that can't be determined with the current methods.

 

[siti]

I think that they are saying, primarily, that the mtDNA method is about as reliable as the other 30 methods that biologists use to identify species.

But that is surely trivial isn't it? That just means that there is sufficiently greater variation in the mtDNA "barcodes" between species than there is within species. Did they at any time suspect that they might find any other result? I get that they are suggesting that mtDNA barcodes might be a 'more reliable' approach where species are closely related enough to make species identification difficult by other methods - but that's really just proposing a new tool for the taxonomists toolkit isn't it?

The other aspect seems to be that there are two (at least) possible explanations, but that neither is currently provable--one explanation being that all species went through a genetic bottleneck...either a single breeding pair, or a population of thousands for thousands of years.

It all hinges on whether or not the bar codes in the mtDNA are neutral or selected for by evolutionary pressure...something that can't be determined with the current methods.

Yes - they make that link but I'm struggling to see it - how does mtDNA variation (esp. if its neutral) point to a speciation or bottleneck when we already know that our direct ancestors included almost everyone of our species alive whose genetic code has survived within the last few hundred to few thousand years anyway? A species that has been around for millions of years would surely have gone through genetic convergence (with or without bottlenecks) many times over - wouldn't it? And its DNA barcode today would reflect that wouldn't it?

What am I missing?

 

[GoodbyeDave]

Part of the problem here is the number of definitions of species that exist. When some-one starts writing about comparing genetic material between species, they must specify exactly what they mean by species or it's pointless.

Fossil species ar established anatomically, living species most often by Mayr's criterion of being a potentially interbreeding group. In practice, paleonologists disagree considerably and many living species used today are legacies: by Mayr's rule, all North American coyotes (Canis latrans), wolves (C. lupus), and dogs (C. familiaris) are actually one species.

 

[beenherebeforeagain]

But that is surely trivial isn't it? That just means that there is sufficiently greater variation in the mtDNA "barcodes" between species than there is within species. Did they at any time suspect that they might find any other result? I get that they are suggesting that mtDNA barcodes might be a 'more reliable' approach where species are closely related enough to make species identification difficult by other methods - but that's really just proposing a new tool for the taxonomists toolkit isn't it?


Yes - they make that link but I'm struggling to see it - how does mtDNA variation (esp. if its neutral) point to a speciation or bottleneck when we already know that our direct ancestors included almost everyone of our species alive whose genetic code has survived within the last few hundred to few thousand years anyway? A species that has been around for millions of years would surely have gone through genetic convergence (with or without bottlenecks) many times over - wouldn't it? And its DNA barcode today would reflect that wouldn't it?

What am I missing?

Apparently the same thing I'm missing!

I certainly don't see anything in the article that would suggest that they are questioning evolution, or suggesting a creation event circa 200,000 BCE, or that all of the species included in the study came from only one mating pair (although they mention it as one form of potential bottleneck...even though there is no evidence to support such an interpretation--and it flies in the face of other biological evidence).

 

[Polymath257]

I came to the same conclusion. The authors seem to be hinting at a massive worldwide speciation event 100k to 200k years ago, but I don't see how the data can support that. You can get mtDNA MRCA's even without a speciation event in a population with a steady and continuous population, so I don't see how you can use intraspeices mtDNA to reliably detect a speciation event and/or a genetic bottleneck unless it is very recent (i.e. last 25,000 years).

You can't use this data to reach that conclusion. From what I can see, they are measuring the collapse time for mtDNA. Now, I would suspect this time goes as the logarithm of population, so would have fairly small variance across species.

 

[Thief]

90% of modern species, including humans, evolved within the last 100-200 thousand years.

Almost all species on Earth today came into being at about the same time, scientific study declares

Scientists are surprised to discover this,and I'm not sure what to make of it.

skipping to my knee jerk response

the life on this planet response to the planet
if one major effect takes place
everything else must follow or die

(meteor crash?)

 

[Thermos aquaticus]

Apparently the same thing I'm missing!

I certainly don't see anything in the article that would suggest that they are questioning evolution, or suggesting a creation event circa 200,000 BCE, or that all of the species included in the study came from only one mating pair (although they mention it as one form of potential bottleneck...even though there is no evidence to support such an interpretation--and it flies in the face of other biological evidence).

You would need to look at more than just a small portion of mtDNA to make any conclusions about a possible population bottleneck.

 

[beenherebeforeagain]

You would need to look at more than just a small portion of mtDNA to make any conclusions about a possible population bottleneck.

That's my thought, too. You'd also have to look for geological and biological evidence that would support a recent bottleneck that would apply to all species equally.

It sounds to me that some of the assumptions about mtDNA inheritance (frequency, nature of changes, etc.) are probably incorrect, and/or there are other factors involved that cannot currently be discerned.

What would help would be a database of the mtDNA for species as they existed circa 150,000 years ago, and those a million years ago...the current sample is looking at a slice of the current situation...