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OptimisticCynic

Evolution Without Pressure

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There is much talk of evolution occurring as a result of survival pressures. Yet the places where the greatest biodiversity can be found are the places where the living is easy, compare the Amazon to the Arctic. I contend that most evolution occurs in places and times of plenty. The basis for this contention is that during times of plenty, more of the in-between mutations survive to reproduce. This allows the more complex mutations and combinations of mutations to develop viable forms. These viable forms may gain significant survival advantages over the old forms. The new, more viable, forms then become the pressure that kills off the old forms.

One advantage to this view of evolution is that it does not require specific environmental factors to guide the selection of intermediate mutations. No purpose or goal is required, unlike the solutions from evolutionary computing.

 

I challenge everyone on this forum to contest my contention. It took me a few minutes (after years of reading for curiosity) to come up with this. How long will it take you to accept it?

 

Hypothesis: More mutations will be found, living, among populations during good times than during lean times. This requires controlling for lean times that occur from circumstances that do not specifically cause mutations.

 

Hypothesis: More diversification of populations occurs in places and times when competitive pressure for resources is lower. The archaeological record supports this. More new species developed soon after major disasters than during the competitive times before the disasters. To extend the hypothesis: the same sort of effect can be seen with reductions in other types of survival pressures upon a species.

 

P.S. Remember, "You are doing the job right only when you are having fun in the process!"

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We can look at some of the predatory species we know of. Some of them ate during times of plenty but then they grew really big. The problem is that when they grew really big they wound up eating all their food then they found themselves extinct because they couldn't feed themselves.

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The Red Queen hypothesis misses my point.

In unchanging conditions of low stress, more complicated variations can arise. In changing or high stress conditions, only simple evolutionary changes are likely to occur because intermediate mutations die too quickly. Compare genotype (simpe) vs phenotype (complex) changes.


fiveworlds,

Yes, it doesn't always work out for the better.

Edited by OptimisticCynic

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There is much talk of evolution occurring as a result of survival pressures. Yet the places where the greatest biodiversity can be found are the places where the living is easy, compare the Amazon to the Arctic.

I think you are playing fast and loose with "survival pressure". Having more niches available for occupation does not mean there is less survival pressure. It might even mean there is more.

Hypothesis: More diversification of populations occurs in places and times when competitive pressure for resources is lower. The archaeological record supports this.

Then you should have no trouble presenting specific examples of this.

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The theory makes sense and is put into practice by humans. For example, medicine deals with threats and stresses caused by disease. If we let these diseases run their course, fewer people would survive such that diversity of the genes would decrease. But with medicine, we make living easier allowing otherwise high risk people, due to disease stress, to reproduce. This can result in the same problems perpetuating, which is not a problem as long as the stress stays low.

 

Say there was a disruption of culture and medical care is disrupted so all the disease stresses return. Those who are here, due to medicine lowering the stress, will see the stress return, and will concentrate down until the genetic pool gets narrower.

 

If you look at sexually transmitted disease, medicine allows promiscuous behavior to flourish, by removing a natural stress. If medicine was disrupted, sexual transmitted disease would spread environmental stress, and many would go extinct.

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We just aren't seeing any pressure for the changes to amount to anything though. The fact that diversity increases with population size is fairly well understood already.

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The theory makes sense and is put into practice by humans. For example, medicine deals with threats and stresses caused by disease. If we let these diseases run their course, fewer people would survive such that diversity of the genes would decrease. But with medicine, we make living easier allowing otherwise high risk people, due to disease stress, to reproduce. This can result in the same problems perpetuating, which is not a problem as long as the stress stays low.

 

Say there was a disruption of culture and medical care is disrupted so all the disease stresses return. Those who are here, due to medicine lowering the stress, will see the stress return, and will concentrate down until the genetic pool gets narrower.

 

If you look at sexually transmitted disease, medicine allows promiscuous behavior to flourish, by removing a natural stress. If medicine was disrupted, sexual transmitted disease would spread environmental stress, and many would go extinct.

What's your evidence that this has actually caused greater biodiversity? If you bring up humans as an example, you have to deal with the vast reduction in biodiversity that we have caused. It sounds like you are talking about genetic diversity, and in that case, you presented no evidence that our genetic diversity has increased. (But that would seem to be OT)

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swansont,

The entire post was fast and loose. This is not my area of expertise by a long shot. That said, here is an article supporting me, http://www.wired.com/2015/03/jay-evolving-weird-way/

A ways down in the article, there is mention of apple maggot flies having diverged into hawthorn tree eaters and apple tree eaters. Should one of those divergent groups diverge again, to take advantage of a different niche, that would support my contention that multiple stage evolution occurs in low pressure situations.

 

For examples from the geologic record I present this excerpt

--from Paleontology article in Wikipedia--

During the Permian period synapsids, including the ancestors of mammals, may have dominated land environments,[75] but the Permian–Triassic extinction event 251 million years ago came very close to wiping out complex life.[76] The extinctions were apparently fairly sudden, at least among vertebrates.[77] During the slow recovery from this catastrophe a previously obscure group, archosaurs, became the most abundant and diverse terrestrial vertebrates. One archosaur group, the dinosaurs, were the dominant land vertebrates for the rest of theMesozoic,[78] and birds evolved from one group of dinosaurs.[74] During this time mammals' ancestors survived only as small, mainly nocturnalinsectivores, but this apparent set-back may have accelerated the development of mammalian traits such as endothermy and hair.[79] After theCretaceous–Paleogene extinction event 65 million years ago killed off the non-avian dinosaurs – birds are the only surviving dinosaurs – mammals increased rapidly in size and diversity, and some took to the air and the sea.[80][81][82]

 

Back to the fast and loose again; I used 'archaeological' which is not the correct term. I think 'geological' record is more correct.

 

 

We just aren't seeing any pressure for the changes to amount to anything though. The fact that diversity increases with population size is fairly well understood already.

Consider two ends of a spectrum of genetic diversity within a species. If hard times applied pressures sufficient to eliminate the population in the middle of that spectrum, the groups on the ends might vary sufficiently to be classified as separate species. Or, after a second or third cycle of good times expansion and diversification of both populations followed by hard times pressures, there would very likely be clear speciation.

 

 

puppypower,

I suspect that the human species is less likely to have long separations of groups because we will, quite literally, go out of our way to interbreed.

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swansont,

The entire post was fast and loose. This is not my area of expertise by a long shot. That said, here is an article supporting me, http://www.wired.com/2015/03/jay-evolving-weird-way/

A ways down in the article, there is mention of apple maggot flies having diverged into hawthorn tree eaters and apple tree eaters. Should one of those divergent groups diverge again, to take advantage of a different niche, that would support my contention that multiple stage evolution occurs in low pressure situations.

 

You have not established that the maggot fly was (or would be) in a "low-pressure" situation. You haven't really defined what that means.

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You have not established that the maggot fly was (or would be) in a "low-pressure" situation. You haven't really defined what that means.

 

A "low pressure"-situation basically means that the environment does not "kill off" anyone due to being unfit.

It goes without saying that this wil initially result in greater biodiversity.

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A "low pressure"-situation basically means that the environment does not "kill off" anyone due to being unfit.

It goes without saying that this wil initially result in greater biodiversity.

 

IOW, a situation that you have not shown to exist, has never existed, and cannot exist. (Unless immortality is a thing)

 

And that would lead to greater genetic diversity, but it's not clear to me that it would necessarily lead to greater biodiversity)

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IOW, a situation that you have not shown to exist, has never existed, and cannot exist. (Unless immortality is a thing)

 

And that would lead to greater genetic diversity, but it's not clear to me that it would necessarily lead to greater biodiversity)

 

We don't need immortality, LOW pressure is not the same as NO pressure.(and creatures dying from old age is no problem)

 

I suppose you 're right that greater genetic diversity does not necessarily mean greater biodiversity (i used the word "initially" as i didn't want to speculate)

but surely greater genetic diversity is a prerequisite for greater biodiversity

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We don't need immortality, LOW pressure is not the same as NO pressure.(and creatures dying from old age is no problem)

 

I suppose you 're right that greater genetic diversity does not necessarily mean greater biodiversity (i used the word "initially" as i didn't want to speculate)

but surely greater genetic diversity is a prerequisite for greater biodiversity

 

Animals not dying off ("the environment does not "kill off" anyone due to being unfit.") can't mean merely low pressure. You said no deaths from the environment. That means no predation, no death from competition for resources, etc. Low pressure would imply some deaths.

 

And, of course, this may not be what the OP meant.

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Animals not dying off ("the environment does not "kill off" anyone due to being unfit.") can't mean merely low pressure. You said no deaths from the environment. That means no predation, no death from competition for resources, etc. Low pressure would imply some deaths.

 

And, of course, this may not be what the OP meant.

 

As long as i 've been alive i 've had no danger to die from competition/predation. Off course i could 've died due to an accident but i call human society "low pressure"

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The relative fitness is the important bit here. If you have low selective pressures it still means that over time those with even slight advantages will be more prevalent. It extends the timeline, though.

The main issue is of course that if talk about diversity we cannot simply use a simple one-dimensional approach focusing exclusively on selection as drivers. If you inspect biodiversity at any time point it is relevant whether the selective force has been present for a long time, or whether it is something that arose recently, for example. It is well known that changes in the environment can lead to rapid evolutionary responses (e.g. by opening new, or closing off ecological niches).

Well-studied recent examples include invasive species such as can toads and how the invasive species themselves but also the native species change due to adaptive as well as non-adaptive processes.

 

See e.g. Shine 2011, Evol Appl. 5:2

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As long as i 've been alive i 've had no danger to die from competition/predation. Off course i could 've died due to an accident but i call human society "low pressure"

You might not have, but plenty of people have on both counts. You can't really paint "human society" with the such a broad brush based on your personal experiences in what I assume is a relatively stable economic situation in a developed country.

 

That said, selection pressure doesn't have to be strictly about predation or competition. Anything that disproportionately suppresses the reproductive rate of a select portion of a population is a selection pressure.

 

In that way, you could consider, for instance, education to be a selection pressure, as it tends to be negatively correlated with number of offspring.

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You might not have, but plenty of people have on both counts. You can't really paint "human society" with the such a broad brush based on your personal experiences in what I assume is a relatively stable economic situation in a developed country.

 

That said, selection pressure doesn't have to be strictly about predation or competition. Anything that disproportionately suppresses the reproductive rate of a select portion of a population is a selection pressure.

 

In that way, you could consider, for instance, education to be a selection pressure, as it tends to be negatively correlated with number of offspring.

Say you have a rich modernized country and a poor backwards country. What we will do is could swap the two populations. This will cause new pressures to appear on the formerly rich because of the extra stresses they will face within the poor country. It will also take away many of the former stresses from the formerly poor, due to the abundance, social security and opportunity in the rich countries. Then we sit back and watch what happens. It is easy to predict.

 

I used medicine, initially, as a way to show a way humans reduce natural environmental stresses, that would cause higher attrition, because many genetic mutations will not survive without medicine. Relatives to the above example, the rich who have previous medical conditions that require modern medicine, will find new stresses, since such services are not common. While those from the poor, will find an extra level of ease, since even hangnails are covered by insurance. This can protect one from themselves.

 

One way, that is not being discussed, that can create lower stress is migration. If one is living in an area where there is a lot of competition and environmental stress one may not have any advantage. However, if you migrate one increases the odds they will find a place with less stress and more advantage. This sudden appearance and selective advantage in the new place, may wrongly be associated with a genetic change or mutation. But it is really due to consciousness reversing engineering an easier environment; migration optimization. This is like the old song says, "I am going to where the weather suits my clothes".

Edited by puppypower

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As long as i 've been alive i 've had no danger to die from competition/predation. Off course i could 've died due to an accident but i call human society "low pressure"

 

But you are not the entire population; some people die from predation. As the joke goes, I don't have to run faster than the bear, I just have to run faster than you. So, not zero pressure.

 

Even with a low-pressure system present for a large fraction of the population, we have not split into multiple species. Humans are not the example you are looking for.

I used medicine, initially, as a way to show a way humans reduce natural environmental stresses, that would cause higher attrition, because many genetic mutations will not survive without medicine.

 

What are some of examples of these many mutations that survive only because of medicine?

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swansont, When you challenge me to do a better job of supporting or defining my contentions, I feel peevish. I thank you for your hard work and request that you keep it up!

 

You have not established that the maggot fly was (or would be) in a "low-pressure" situation. You haven't really defined what that means.

A "low pressure" situation is a situation wherein difficulties that threaten the lives of somewhat less optimally suited individuals are reduced. It's all relative. I do not see an objective way to define "low" or "high" selective pressures. The closest objective measure I imagine would be above or below the average mortality rate, as measured over a many generations long period, of immature individuals. The low, or reduced, stress situation would have to continue over multiple generations to enable variations to combine as I've suggested.

Puppypower mentioned migrations to different environments as a possible mechanism for reduction in selective pressures. The apple maggot fly adaptation might be called a migration. I really do not see species like the maggot flies as likely to provide good examples of this low pressure evolution because of the boom and bust nature of their life cycles. A better example might be found in a population of sheep which is outgrowing its territory and has a lot of unclaimed territory to expand into because of more rain than there used to be. Those sheep with more wool would tend to migrate toward cooler territories while those with less migrated to warmer territories. More migrations to new territory will succeed when the conditions between optimal territories are better able to support the migrating animals (during good years).

In such a case, it is the genetic variation which pressures the population to separate. This is opposite to the idea of external factors pressuring the animals to change genetically. Going back to the apple maggot flies, there would have been, in the original population, some flies which found both hawthorns and apples to be acceptable places to lay eggs. Others would find only hawthorns acceptable. Those which found hawthorns unacceptable did not lay eggs. Then a new option appeared and some flies which would not lay eggs on hawthorns had an acceptable place to lay their eggs. The selection pressure against these specific flies disappeared and they became numerous enough to "suddenly" appear.

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A "low pressure" situation is a situation wherein difficulties that threaten the lives of somewhat less optimally suited individuals are reduced. It's all relative. I do not see an objective way to define "low" or "high" selective pressures.

If you can't define it, then that's a big problem. For all we know from what you've presented, the maggot fly may have speciated because of high selective pressure. Otherwise why adapt to a new food source?

 

The closest objective measure I imagine would be above or below the average mortality rate, as measured over a many generations long period, of immature individuals. The low, or reduced, stress situation would have to continue over multiple generations to enable variations to combine as I've suggested.

Puppypower mentioned migrations to different environments as a possible mechanism for reduction in selective pressures. The apple maggot fly adaptation might be called a migration. I really do not see species like the maggot flies as likely to provide good examples of this low pressure evolution because of the boom and bust nature of their life cycles. A better example might be found in a population of sheep which is outgrowing its territory and has a lot of unclaimed territory to expand into because of more rain than there used to be. Those sheep with more wool would tend to migrate toward cooler territories while those with less migrated to warmer territories. More migrations to new territory will succeed when the conditions between optimal territories are better able to support the migrating animals (during good years).

Outgrowing your territory sounds like a high selection-pressure situation. Too many individuals for the resources available.

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And that's really an important point. If a population speciated in order to exploit a new niche, or series of new niches, it means that a sub-group within that population was better able to reproduce by exploiting a new strategy than the existing one, which implies that their reproductive fitness under the old model was comparatively suppressed in order for the new strategy to yield better results.

 

Maybe there was less available energy for reproduction under the old system, maybe there was more competition, maybe there was less physical space in a necessary environment.

 

And in any case, "low" pressure being poorly defined really is a problem. Say you have a relatively new species of tightrope walker. There's a whole unexploited environment of tightropes with plenty of room and food for billions of them, so lots of room for expansion of the species, and no predators whatsoever that can reach them as they run along the ropes. And they can exploit this environment because they are all expert tightrope walkers that never fall.

 

That seems fairly low pressure, right? But is it? Because if any individual winds up being born that isn't so good at tightrope walking, they fall and die. That's a very small portion of the population of new births, and so could be relegated to the territory of "birth defect" but still. The environment is maintaining the population within an a range that is still capable of exploiting the environment that resulted in their abundance and success. They might not be killed off left and right by environmental dangers, but they still have a boundary on the directions that can fan out in evolutionarily.

 

I think that any "low pressure" system that you could conceive of is still going to have a lot of these "hidden boundaries" that don't really seem like they are selection pressures any longer because the population in question has adapted to deal with them very well, or because they exist ist he fringes of he population's environment and so are rarely encountered, but which nevertheless present limits to the directions and vareity that the population can evolve in.

 

A ground animal that can't climb trees doesn't seem like it would have an exclusively tree-dwelling predator as a selection pressure, for instance, but if any of them that did try climbing trees would immediately get eaten, there is a selection pressure against the evolution of climbing.

 

If the bright yellow berries that none of them eat are poisonous, it might not seem like much of a selection pressure, but it does mean that there is a selection pressure against eating small yellow fruits and anyone who evolves away from this aversion is likely to wind up dead.

 

You can't just assume that all of the traits that allow an organism to survive and avoid the pitfalls of their environment are a given at that they are therefore not subject to much selection pressure. There is likely to be a fairly strong selection pressure to maintain those traits even if the frequency with which that pressure comes into play is fairly low because the genes that might fall afoul of the pressure in question have long since been weeded out and new mutations are rare and quickly eliminated.

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To recap:

Most evolution occurs in times of plenty.

During times of plenty, more of the in-between mutations survive to reproduce. Plentiful resources allows the more complex combinations of mutations more time and space to develop viable forms.

During times of plenty, genetically varied individuals of a species are able to travel further and have better odds of finding a habitat that their variations suit better. This wandering around looking for a situation that is a better fit tends to bring individuals with the same or similar characteristics together in places where they are more likely to successfully proliferate. It also tends to separate groups with disparate characteristics.

 

 

Hypothesis: The scrub jays of Santa Cruz island produce offspring with variations in bill length. Those with longer bills will move to the pine forests. Those with shorter bills will move to the oak forests. The birds select their habitats while they are still juveniles. Then they stay in their selected habitats as adults and breed there. http://www.wired.com/2015/03/jay-evolving-weird-way/

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To recap:

Most evolution occurs in times of plenty.

During times of plenty, more of the in-between mutations survive to reproduce. Plentiful resources allows the more complex combinations of mutations more time and space to develop viable forms.

During times of plenty, genetically varied individuals of a species are able to travel further and have better odds of finding a habitat that their variations suit better. This wandering around looking for a situation that is a better fit tends to bring individuals with the same or similar characteristics together in places where they are more likely to successfully proliferate. It also tends to separate groups with disparate characteristics.

 

IOW, when there are more niches to exploit there will be more speciation.

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