12 replies to this topic

[QuestforLife]

Telomeres are known to shorten in the stem cells of somatic tissues, contributing to aging of the organism. This much is well known. What is less well known is that telomeres also appear to shorten between generations (https://www.ncbi.nlm...pubmed/25952108). It was originally thought to be due to the ‘old father effect’, by which older men father children with longer telomeres – and that this was somehow due to sperm lengthening telomeres with age (to my knowledge this has never been proven by a longitudinal study). However, it is now believed that this is a birth cohort effect, with each subsequent generation born with shorter telomeres than the one before (therefore having an older dad means that you’ve skipped some of this shortening). If proven true (and this theory explains how evolution brings about new species) then it means that species age and die out (or suddenly evolve) through telomeric shortening, and that human beings have likely accelerated this process recently by having children later in life. This is because  the proposed mechanism for this intergenerational telomere attrition is the aging through division of the mother’s ooctyes (https://www.ncbi.nlm.nih.gov/pubmed/24493020).

 

It is well known that older mothers’ eggs often suffer from aneuploidy, i.e. the wrong number of chromosomes, and this is likely due to chromosome fusions and rearrangements caused by attrition of the eggs’ telomeres. (https://www.ncbi.nlm...pubmed/28327364, https://www.thelance...516-4/fulltext)

I am well aware this theory is ‘out there’, but it has such astounding consequences if true, that it deserves proper attention and discussion.

Edited by QuestforLife, 25 June 2019 - 02:12 PM.

[QuestforLife]

More support for the idea that the unleashing of transposable elements can lead to rapid evolution:

 

https://www.earlham....-evolution-mice

https://genome.cshlp...7.full.pdf html

 

Generally this is proposed to occur when TEs are near a chromosome break point, which then leads to a re-pattening of the genome (and a new phenotype) within the new chromosome/s. However it is also possible that re-pattening can occur within existing chromosomes (possibly due to methylation changes?), and this might explain the huge phenotype variation within dog breeds that are nonetheless still one species because they have the same karytope (chromosomes). 

 

https://link.springe...335-019-09812-5

 

One can also imagine the opposite situation - whereby new chromosomes are formed but repatterning of the genome does not (because no TEs are near the break points or because the chromosome changes are due to fusion of smaller chromosomes), so the new species is very similar to the old one, even though they cannot interbreed. We can see evidence for this in the many, many species of extremely similar mice.

 

 

Edited by QuestforLife, 02 September 2019 - 09:14 AM.

[marcobjj]

Thanks for the info. I personally don't believe this, but it could be the plot for an interesting scifi novel 

[QuestforLife]

Thanks for the info. I personally don't believe this, but it could be the plot for an interesting scifi novel 

 

It does seem far fetched on first glance, but it does explain a lot of things.

 

For example: telomere length is always said to be 'reset' at the embryo stage. Where is the proof of this? And if this is the case, why would any telomere length be inherited, as has been shown to occur. More likely is that you inherit an average of the TL of your Dad's sperm and your Mum's egg, and then the embryo replicates with telomerase so it does not lose any more, until cells start differentiating and passing the pluirpotency threshold.

 

Another example: why does every extinction always require some big disaster? Like killing the dinosaurs required a meteor? Or human hunters killing mammoths? Or climate change killing XYZ? And why do new species always have to be separated by a river or an ocean or some other barrier to form? More examples: bees are dying because of pesticides - only they're not. And Tasmanian Devils dying because of a weird infectious mouth cancer that no one can explain.

 

Is it not possible that rapid evolution is built into the chromosomes, and that slower, phenotypic evolution such as we see now and discovered by Darwin, is actually just the minor part of evolution, when the new species are gradually tailored to their environment.

 

It also undercuts the arguments around the evolution of aging, and why some species can regenerate, why some species can't regenerate but don't age, but how mammals can't do either - because of course doing that would cause cancer, wouldn't it?!? 

 

It makes much more sense to me that there is a map of all possible chromosome combinations, and that each species is somewhere within this plan - and it is likely to be possible to see where each species is going next, based on the chromosomes with the shortest telomeres.

[Turnbuckle]

It does seem far fetched on first glance, but it does explain a lot of things.

 

For example: telomere length is always said to be 'reset' at the embryo stage. Where is the proof of this? And if this is the case, why would any telomere length be inherited, as has been shown to occur. More likely is that you inherit an average of the TL of your Dad's sperm and your Mum's egg, and then the embryo replicates with telomerase so it does not lose any more, until cells start differentiating and passing the pluirpotency threshold.

 

Another example: why does every extinction always require some big disaster? Like killing the dinosaurs required a meteor? Or human hunters killing mammoths? Or climate change killing XYZ? And why do new species always have to be separated by a river or an ocean or some other barrier to form? More examples: bees are dying because of pesticides - only they're not. And Tasmanian Devils dying because of a weird infectious mouth cancer that no one can explain.

 

Is it not possible that rapid evolution is built into the chromosomes, and that slower, phenotypic evolution such as we see now and discovered by Darwin, is actually just the minor part of evolution, when the new species are gradually tailored to their environment.

 

It also undercuts the arguments around the evolution of aging, and why some species can regenerate, why some species can't regenerate but don't age, but how mammals can't do either - because of course doing that would cause cancer, wouldn't it?!? 

 

It makes much more sense to me that there is a map of all possible chromosome combinations, and that each species is somewhere within this plan - and it is likely to be possible to see where each species is going next, based on the chromosomes with the shortest telomeres.

 

Species evolve to fit their environments, and thus become sensitive to sudden changes in those environments. Many become overspecialized and find it hard to despecialize. Birds, for instance, weren't able to restore their front limbs even after many became flightless after the Cretaceous extinction. If they could have, they might have taken over and become the dominant group. Humans too are evolving due to cultural pressures that make them more sensitive to a global catastrophe. Brain size is shrinking and the ability to smell has declined, due to the necessity of surviving idiot leaders and tolerating large (and stinky) groups. That humans live as long as they do was driven by cultural forces. Until the advent of writing and mass literacy, old people were needed as reservoirs of cultural information. Now they are just a burden on society, so there's no longer any evolutionary pressure to keep them.

 

Telomeres are how cells age, not species. Without this clever innovation, you wouldn't live very long, as many tissues proliferate quickly and age quickly. Without some mechanism of keeping track of proliferative age and getting rid of the old ones, you would be overwhelmed with dysfunctional cells in the most critical areas. Not all tissues recycle this way, but telomeres play a part in many. Without telomeres as a check on growth, you would have much more cancer, and without them epigenetic mutations would increase relentlessly until your cells became as specialized as protoplasm. Your bones would become weak, your skin thin and splotched, and your hair would fall out. You would become old, in other words.

Edited by Turnbuckle, 09 September 2019 - 09:41 AM.

[QuestforLife]

Species evolve to fit their environments, and thus become sensitive to sudden changes in those environments. Many become overspecialized and find it hard to despecialize. Birds, for instance, weren't able to restore their front limbs even after many became flightless after the Cretaceous extinction. If they could have, they might have taken over and become the dominant group. Humans too are evolving due to cultural pressures that make them more sensitive to a global catastrophe. Brain size is shrinking and the ability to smell has declined, due to the necessity of surviving idiot leaders and tolerating large (and stinky) groups. That humans live as long as they do was driven by cultural forces. Until the advent of writing and mass literacy, old people were needed as reservoirs of cultural information. Now they are just a burden on society, so there's no longer any evolutionary pressure to keep them.

 

Telomeres are how cells age, not species. Without this clever innovation, you wouldn't live very long, as many tissues proliferate quickly and age quickly. Without some mechanism of keeping track of proliferative age and getting rid of the old ones, you would be overwhelmed with dysfunctional cells in the most critical areas. Not all tissues recycle this way, but telomeres play a part in many. Without telomeres as a check on growth, you would have much more cancer, and without them epigenetic mutations would increase relentlessly until your cells became as specialized as protoplasm. Your bones would become weak, your skin thin and splotched, and your hair would fall out. You would become old, in other words.

 

The argument is not whether Darwin's ideas on gradual evolution of traits is true or not(it is), but whether gradualism can explain everything or whether there are other mechanisms at play. Gradualism doesn't seem to have a good explanation for why so many species have come and gone, or why so much of evolution happens in short bursts. That is why they always have to rely on some kind of catastrophe. Likely changes in environment do play a part in the emergence of species but when you actually look at what a species is, i.e. not being able to interbreed due to different chromosome numbers, you see that some sort of sudden genetic transformation is required.

 

Looking at the common ancestor of humans and gibbons for example, you can actually map out how the chromosomes have mixed and matched with these events. How many catastrophes could there have been in that time? Interestingly you can still see within the larger human chromosomes small sections of telomeres within the chromosome showing us where the ends were. You also get chromosomes that fuse when telomeres erode away - this happens with cancer, and it seems also in the genesis of new species. 

 

Anyway, these are the ideas of Reinhard Stindl. They may be wrong or right, but I think they are interesting and deserve consideration. 

 

I don't see telomeres and epigenetic age as opposing forces, Turnbuckle. Yes you are right, cell lines require replacement from a good 'blue print' and without this would eventually 'drift'.  But having sufficient telomeres in stem and progenitor cells would actually encourage apoptosis in damaged somatic cells, I think - as opposed to senescence, which happens partly because the body knows it doesn't have ready replacements.

 

It would be interesting to see what we can learn from animals that don't cross the adult transition (and stop growing). Presumably they have telomerase in stem cell compartments, but what about epigenetic aging due to methylation? And what about cancer.  Perhaps they suffer from neither.

[Turnbuckle]

Evolution occurs at all speeds, and environmental change speeds things up. There's no mystery to it. As for primate evolution, this wasn't exactly rapid, as the first proto-primates have been traced back to more than 65 million years ago. But I don't see how any of this connects with telomeres. In fact, I'm not clear on what exactly you are arguing. Do species age? Was that it? In my opinion, they don't. They only become overly specialized and thus non-competitive with new species and unable to cope with environmental changes.

[QuestforLife]

The point is that speciation happens rapidly. and this might not require environmental change. 

 

Telomeres are relevant because their erosion in the germline is the proposed mechanism for sudden extinction and emergence of new species.

 

This thread was mostly a brain dump, so apologies if it is not clear.  

 

The theory is here: https://www.telomere.at/index.html

 

Evidence that telomeres are shortening between generation is here: https://www.ncbi.nlm...pubmed/25952108

 

 

 

 

[Turnbuckle]

The idea of a species clock is an interesting idea for science fiction, but that's about it.

[Mind]

What about the species that have been around for hundreds of millions of years, like some reptiles. Those species don't seem to have aged.

[QuestforLife]

What about the species that have been around for hundreds of millions of years, like some reptiles. Those species don't seem to have aged.

Maybe they are not the same species that has been 'around for hundreds of millions of years.' Maybe they just look the same, like the many species of mouse.

The other possibility is that a species that itself doesn't age on an individual animal level, or ages very slowly (like turtles), may be around for much longer because it's germline is also much more durable.

[marcobjj]

 

Another example: why does every extinction always require some big disaster? Like killing the dinosaurs required a meteor? Or human hunters killing mammoths? Or climate change killing XYZ? And why do new species always have to be separated by a river or an ocean or some other barrier to form? More examples: bees are dying because of pesticides - only they're not. And Tasmanian Devils dying because of a weird infectious mouth cancer that no one can explain.

 

 

 

Recorded history is a small percentage compared to the fossil record of most species, which makes extinction not easily observable or well understood phenomenon. I think the environmental theories for the extinction of pre historic species is simply Occam's Razor - We have observed the the extinction of the Dodo bird and the Tasmanian Tiger among others, due to predatorial action. 

 

Dinosaurs were multiple species, so their clock would have to be at a higher taxonomic level, like an Order clock, or it's an extreme coincidence that they all expired seemingly around the same time peroid.

Edited by marcobjj, 10 September 2019 - 06:56 AM.

[QuestforLife]

Recorded history is a small percentage compared to the fossil record of most species, which makes extinction not easily observable or well understood phenomenon. I think the environmental theories for the extinction of pre historic species is simply Occam's Razor - We have observed the the extinction of the Dodo bird and the Tasmanian Tiger among others, due to predatorial action. 

 

Dinosaurs were multiple species, so their clock would have to be at a higher taxonomic level, like an Order clock, or it's an extreme coincidence that they all expired seemingly around the same time peroid.

 

On the contrary, the fossil record can no longer be regarded as incomplete.

 

From Stindl's most important paper (https://link.springe...0114-014-1152-8) quoting respected American paleontologist Steven M. Stanley ( in Stanley SM (1984), 'The new evolutionary timetable: fossils, genes, and the origin of species' Basic Books, New York):

 

.... the Pleistocene sediments at thousands of collecting sites have uncovered at least 85 % of the mammalian species living today, and therefore the fossil record can no longer be regarded as providing an incomplete picture of evolution (Stanley 1984, p. 97). Most importantly, Stanley mentions the puzzling paleontological fact that within less than 12 million years, most of the living orders of mammals developed, including such diverse animals as lions, wolves, bears, horses, rhinos, deer, pigs, antelopes, sheep, bats and whales, all having descended from a tiny animal resembling a small rodent (Stanley 1984, p. 93). He further concluded: “We can now show that fossil mammal populations assigned to a particular Cenozoic lineage typically span the better part of a million years without displaying sufficient net change to be recognized as a new species. (…) If an average chronospecies lasts nearly a million years, or even longer, and we have at our disposal only ten million years, then we have only ten or 15 chronospecies to align, end-to-end, to form a continuous lineage connecting our primitive little mammal with a bat or a whale” (Stanley 1984, p. 93). “Our only reasonable recourse is to abandon gradualism in favor of punctuated evolution, which can account for the rapid changes for which we see evidence. These changes must have been brought about by strongly divergent steps that came in rapid succession”

 

If you read this paper, you'll see all the dinosaurs disappearing in the same period is exactly as expected.

 

This figure gives a nice overview. In a nutshell it's showing that there are long periods of slow evolution where species change and sometimes fork off into subspecies, but otherwise don't change much (Darwinian evolution) and then their are massive changes where most new genus of species appear. The mechanism for these steps are chromosomal changes; firstly erosion of telomeres in smaller chromosomal arms causes fusions (this is what is happening in humans in chromosomes 13, 14, 15 and 21, (I believe))  and then once this can go no further the big chromomsomes break up and total rearragements occur. Read the paper for a more thorough understanding.