Evolution Question

[Senator Cheese]

This is an honest question and I do hope I'll better understand rudimentary biology that way. For all intents and purposes, I shall define "beneficial" mutations as mutations that further reproduction or survival and "malignant" mutations as those that hamper procreation or lead to observable detrimental effects.

While it is easy to imagine natural selection working on organisms that reproduce in great numbers under limited resources (where malignant mutations would inhibit reproduction), I am having problems applying this to higher organisms.

1.) Malignant mutations may manifest only after an organism has procreated or even fail to inhibit procreation altogether while still causing disease.
2.) Furthermore, given all we know about biochemistry, the odds of a mutation being malignant/indifferent are multitutes higher than a mutation being beneficial.
3.) Additionally, it is fair to say that as the complexity (determined by the amount and amino-acid length of proteins involved in any cellular pathway) of a given polypeptide/protein increases, the odds that a mutation will lead to loss of function rather than a gain of function (which can, in most cases, translate to a beneficial genetic code turning malignant), will also increase.

Wouldn't it be standing to reason that as the complexity of an organism increases, the speed of evolution will decrease and potentially even reach a point in which the population consists of individuals that are potent to procreation but at the same time riddled with disease that manifests after the age of procreation?
Noting that natural selection is also subject to statistical dispersion (i.e. there can be "lucky" organisms that survive though they are less fit than "unlucky" organisms), wouldn't there be a "maximum" level of evolution at the point where beneficial mutations become so rare that the effects of statistical dispersion negatively affecting natural selection exceed that rate?

Sorry for the English and thanks for the help!

 

[DogmaHunter]

Good questions!

I don't think I can answer them all as I'm not an evolutionary biologists, but I'll share some of my thoughts.


The first thing we need to remind ourselves of here, is that evolution is a slow, gradual and incremental process. All to often I encounter people who think of evolution as an individual growing a set of wings and passing on the treat. Not that you are implying such things here, but you seem to be hinting at it.

I get what you say about complexity making it harder to get to further evolutionary changes. In some ways, you might be correct - but not in the way you mean it here.


As organisms grow more complex, usually that goes hand in hand with a much stricter selection process as the complex organism inhabits a tighter and tighter environment. If nothing else changes, we get something that is called a "local optimum". Crockodiles find themselves in that stage for example. Top of the food chain, strict environment to inhabit, great at what they do. Aside from evolutionary changes that makes them immune to certain deseases etc, I wouldn't expect the "form" of the crock to drastically change any time soon.


Next, we need a clear distinction with big changes (as resulting from long periods of time with many, many generations) and small changes (as resulting from shorter periods of time with not that many generations).

Consider humans as an example.
We are all homo sapiens. We all find our ancestry in Africa, which was also homo sapiens. Several groups left the "motherland" and migrated to other parts of the world (asia, the americas, australia, europe). The result of this was a genetic isolation of these groups for thousands of years. The result of that isolation? Well, it's plain to see... How come you know immediatly from the look of someone's face where his geographic ancestry is?


You immediatly recognise someone with ancestry in Africa.
You immediatly recognise someone with ancestry in Asia.
You immediatly recognise someone with ancestry in Australia (aboriginals).


This is the result of (short term) evolution.

Let's go a step further and compare ourselves with the closest cousin: chimps. Some 8 million years (give or take) of evolution resulted in the net-difference between chimps and humans.


We sure look vastly different. We sure behave vastly different. They can do things we can't do at all (and not just swing from tree to tree - they also have incredible photographic short term memory that no human can match, among other things). Likewise, we can do things they can't do at all - or even think of doing-, like build a space shuttle.


But nevertheless, eventhough we look and behave so vastly different, the truth of the matter is that we aren't actually THAT different. Our DNA is an incredible match, with only very little difference (at least: far less then our differing looks would suggest at first glance). According to some comparing techniques (there are several), we share some 98.5% of DNA. So our ENTIRE difference is within that 1.5%
So, from that we can already conclude that it might not really take that much in genetics to result in big physiological changes.

It goes further though, once we look at the insides of a chimp and a human... we see even less difference. Our skeletons are roughly identical in anatomical build-up. So are our organs and such.



Now, about the "lucky" and "unlucky" organisms... this isn't a problem at all. Yes, sometimes the "best fit" will get eaten by a predator anyway before reproducing. Likewise, sometimes a "not-so-fit" will succeed in reproducing where a "better fit" might have failed. This happens all the time and is not a problem.

We only speak about an evolutionary change once a specific mutation/change achieves fixation in a population. This mean that the change has become so widespread in the population that it became a solid part of the genepool.

This doesn't happen in one or two generations. It actually takes quite some time before such a change can spread in the entire population.

If a "bad" mutation slips through in generation 1, it still has a loooooong way to go before becoming part of the genome. And most likely, it won't happen. It will be weeded out in subsequent generations.


About desease that happens after procreation... yes. We have lots of those. Cancer arguably being one of them.


If the genetics that allows cancers to grow would also mess up reproduction, then those cancers would have been weeded out long ago. Well, that or the human species would have gone extinct.

 

[TLK Valentine]

This is an honest question and I do hope I'll better understand rudimentary biology that way. For all intents and purposes, I shall define "beneficial" mutations as mutations that further reproduction or survival and "malignant" mutations as those that hamper procreation or lead to observable detrimental effects.

While it is easy to imagine natural selection working on organisms that reproduce in great numbers under limited resources (where malignant mutations would inhibit reproduction), I am having problems applying this to higher organisms.

1.) Malignant mutations may manifest only after an organism has procreated or even fail to inhibit procreation altogether while still causing disease.

Not always -- the mutation would be present in the offspring; which may never get the chance to procreate as a result.

2.) Furthermore, given all we know about biochemistry, the odds of a mutation being malignant/indifferent are multitutes higher than a mutation being beneficial.

True -- the vast majority of mutations are neutral; what you're calling "indifferent." They don't affect an organism's chances of reproduction in any way.

3.) Additionally, it is fair to say that as the complexity (determined by the amount and amino-acid length of proteins involved in any cellular pathway) of a given polypeptide/protein increases, the odds that a mutation will lead to loss of function rather than a gain of function (which can, in most cases, translate to a beneficial genetic code turning malignant), will also increase.

Remembering that a "malignant" mutation is only one that hinders an organism's chance of reproduction, the odds of a mutation being neutral are far more likely.

Furthermore, DNA is far from a well oiled machine; there's plenty of junk in the system, as it were -- holdovers from the past. A mutation may very well affect a useless genetic code.... the most likely effect being that it remains useless.

Wouldn't it be standing to reason that as the complexity of an organism increases, the speed of evolution will decrease and potentially even reach a point in which the population consists of individuals that are potent to procreation but at the same time riddled with disease that manifests after the age of procreation?

Not 100% sure what you're saying here -- It would stand to reason that as species become more complex, the changes that we see will become far more subtle and less noticeable, but it's the environment that determines the "speed" of evolution -- and that speed isn't constant, and not predictable.

All it takes is any kind of change in the environment -- climate shift, introduction of a new predator, asteroid impact, alien invasion, zombie apocalypse, whatever -- and what constitutes a beneficial, neutral, or harmful mutation can change practically overnight.

Noting that natural selection is also subject to statistical dispersion (i.e. there can be "lucky" organisms that survive though they are less fit than "unlucky" organisms), wouldn't there be a "maximum" level of evolution at the point where beneficial mutations become so rare that the effects of statistical dispersion negatively affecting natural selection exceed that rate?

I think human beings may be close to that point already, but not due to statistics. Remember that natural selection is determined by how well (or how poorly) an organism adapts to its environment.

As humans, we no longer adapt to our environment; we've developed the technology to modify our environment to adapt to us. That takes a lot of pressure off evolution.

Sorry for the English and thanks for the help!

you're welcome, and you're doing fine.

 

[Split Rock]

This is an honest question and I do hope I'll better understand rudimentary biology that way. For all intents and purposes, I shall define "beneficial" mutations as mutations that further reproduction or survival and "malignant" mutations as those that hamper procreation or lead to observable detrimental effects.

While it is easy to imagine natural selection working on organisms that reproduce in great numbers under limited resources (where malignant mutations would inhibit reproduction), I am having problems applying this to higher organisms.

1.) Malignant mutations may manifest only after an organism has procreated or even fail to inhibit procreation altogether while still causing disease.
2.) Furthermore, given all we know about biochemistry, the odds of a mutation being malignant/indifferent are multitutes higher than a mutation being beneficial.
3.) Additionally, it is fair to say that as the complexity (determined by the amount and amino-acid length of proteins involved in any cellular pathway) of a given polypeptide/protein increases, the odds that a mutation will lead to loss of function rather than a gain of function (which can, in most cases, translate to a beneficial genetic code turning malignant), will also increase.

Wouldn't it be standing to reason that as the complexity of an organism increases, the speed of evolution will decrease and potentially even reach a point in which the population consists of individuals that are potent to procreation but at the same time riddled with disease that manifests after the age of procreation?
Noting that natural selection is also subject to statistical dispersion (i.e. there can be "lucky" organisms that survive though they are less fit than "unlucky" organisms), wouldn't there be a "maximum" level of evolution at the point where beneficial mutations become so rare that the effects of statistical dispersion negatively affecting natural selection exceed that rate?

Sorry for the English and thanks for the help!

Detrimental traits that do not alter fitness will indeed not be selected against... think most forms of cancer, for example. Most mutations are neutral, but can be beneficial (or detrimental) under different circumstances. Why would beneficial mutations become more rare over time? Rarity is most affected by selective pressure. In other words, beneficial mutations are more rare under stabilizing selection, in which the status quo tends to be maintained.

 

[digitalgoth]

Noting that natural selection is also subject to statistical dispersion (i.e. there can be "lucky" organisms that survive though they are less fit than "unlucky" organisms), wouldn't there be a "maximum" level of evolution at the point where beneficial mutations become so rare that the effects of statistical dispersion negatively affecting natural selection exceed that rate?

I believe you're referring to genetic drift, which is the statistical change in the frequency in an allele over time not necessarily controlled by natural selection and mutation, but more as to what frequency those things are passed on to offspring. There is some debate over the strength of genetic drift changing allele frequency compared to natural selection directly and how alleles can become fixated.

The computer models of evolution I personally am involved with are interesting in that most mutations are "bad", and are quickly selected out. As a bad example, think about how before modern medicine half of children wouldn't survive to become teens, and now we can keep a variety of children alive, whether they are blind, deaf, premature, have mental problems, etc., where they wouldn't have been alive long enough to propagate in the past. Humans no longer are really bound to natural selection, because our technology and social apparatus allow humans to survive that normally wouldn't if we were living in the middle of the jungle with predators all around.

I work with computer models that use evolution, and what you're describing, the idea of evolution "stopping" also occurs, and by with I mean that the selection pressures become to low to actually slow down large scale changes to the population. As a previous post stated, crocodiles (and sharks) have largely not changed from millions of years ago, because both are pretty much apex predators in their environments, have long lives with resistance to many forms of disease, and therefore there isn't heavy selection pressures from environmental changes.

Other things, like drug resistant bacteria with high reproduction rates, have evolved quite quickly to have gained "beneficial" mutations to help with their survival. Their environment is deadly and they quickly select out "bad" mutations and move the population in a different direction.

This is off topic, but I have a theory about humans. We've clearly removed almost all of our selection pressures due to technology and our control over our environments. We can live in temperature extremes, we are omnivorous and can eat almost anything and survive, from whale blubber and insects to almost any creature and plant on Earth. Tool use allows us to survive where it's 130 degrees to -30 degrees. Our technology allows us to save and sustain our lives for incredible amounts of time despite many illnesses and diseases that would wipe us out. Our natural evolution has been effectively taken out of nature's hand, which means a lot of mutations are not being selected out nor being excessively propagated in ways that would happen in a more dangerous environment where the smallest competitive advantage in survival quickly can spread through the population. Which means we're more similar to crocodiles and sharks and other slower evolving animals.

Normally I'd be cynical about this, which was the same stupid ideas that caused a lot of bad ideas with eugenics in the early part of the 20th century. The "[bless and do not curse][bless and do not curse][bless and do not curse] we've got to get rid of all the bad people with icky genes" that was prevalent in the US and Europe at the time and became implemented by Germany in WW2.

However I see this as a good thing. Mutations aren't good or bad, they just express themselves in a way that can do some useful things depending on our environment, much like how resistance to malaria and sickle cell anemia are linked together, beneficial in one case and not in another.

This is just my opinion, but what slowing our selection process and propagating our neutral mutations are doing is actually building up our raw materials for a change in the environment. Evolution uses two things, exploiting our existing genetic options (selection) which is useful when selection pressures are raised from environmental stress, and exploring new information (which mutation provides) which contribute new options to our genetic code. Should environmental pressures increase (say solar flares wipe out all electricity, wars break out, disease is rampant, etc.) our complexity and large genetic code base give us an advantage in surviving such a scenario because we have more initial raw material and diversity of genetic code to evolve with.

Now evolution hasn't "stopped". It never stops as mixing DNA with two parents with mistakes and mutations creeping into the system continues to cause change, however it just doesn't appear to be as "fast" as other organisms who are in environments where selection pressures are stronger and it causes the population to promote changes that benefit the organism in those environments.

 

[[serious]]

This is an honest question and I do hope I'll better understand rudimentary biology that way. For all intents and purposes, I shall define "beneficial" mutations as mutations that further reproduction or survival and "malignant" mutations as those that hamper procreation or lead to observable detrimental effects.

While it is easy to imagine natural selection working on organisms that reproduce in great numbers under limited resources (where malignant mutations would inhibit reproduction), I am having problems applying this to higher organisms.

1.) Malignant mutations may manifest only after an organism has procreated or even fail to inhibit procreation altogether while still causing disease.
2.) Furthermore, given all we know about biochemistry, the odds of a mutation being malignant/indifferent are multitutes higher than a mutation being beneficial.
3.) Additionally, it is fair to say that as the complexity (determined by the amount and amino-acid length of proteins involved in any cellular pathway) of a given polypeptide/protein increases, the odds that a mutation will lead to loss of function rather than a gain of function (which can, in most cases, translate to a beneficial genetic code turning malignant), will also increase.

Wouldn't it be standing to reason that as the complexity of an organism increases, the speed of evolution will decrease and potentially even reach a point in which the population consists of individuals that are potent to procreation but at the same time riddled with disease that manifests after the age of procreation?
Noting that natural selection is also subject to statistical dispersion (i.e. there can be "lucky" organisms that survive though they are less fit than "unlucky" organisms), wouldn't there be a "maximum" level of evolution at the point where beneficial mutations become so rare that the effects of statistical dispersion negatively affecting natural selection exceed that rate?

Sorry for the English and thanks for the help!

Some good thoughts! A few items to consider though:
1. Should we see mutations that cause health problems after fertility ends? While I don't have hard an fast numbers or anything, I can't think of too many animals that greatly outlive their reproductive lives. Generally, we do see old age related breakdowns after fertility is lost. Many diseases of old age in humans, for example, begin around the time of menopause. We've seen from some animals like lobsters that senescence (biological aging) doesn't HAVE to happen. The cessation of telomerase, a key aspect of aging, could certainly be a perfect example of a "bad" mutation that got fixed in the population because it didn't really set in until after reproduction.

2. Does fitness end when reproduction ends? Another factor to consider is that in species that care for their young, there is a second order reproductive benefit to living a while after the last offspring.

3. Is there an optimal evolution after which all further change would be bad? For a given environment and niche, perhaps, but functionally no. The environment changes with time, sometimes slowly, sometimes quickly. What you get is two types of "optimal" Short term optimal can be approached by specialists. Some moth is perfectly adapted for feeding on one flower in one place and no other moth can compete with it in feeding on that flower. Some animals play the long game. A different moth might not be the very best at feeding on any one flower, but is reasonably able to feed on lots of different flowers. If Flower A is doing well one year, they can feed on that. If flower B is doing well the next, they are there to feed on that.

4. Do complicated pathways tend to end up with loss of function rather than gain of function? Not really. "gain of function" is generally more of "change in function" which even complicated pathways can end up with. Some of those genes have lots of copies which functionally allows them to maintain the old function while one copy changes and gives an alternate function. One could imagine, for example, a hemoglobin gene duplicating (the number of copies of hemoglobin are variable generation to generation) and one copy ending up with a different binding affinity. This could be beneficial even if it's providing a different function. For example, say a species lives some where prone to releases of carbon monoxide. Having a second mutant type of hemoglobin which binds tightly to carbon monoxide may free up the regular hemoglobin to keep carrying oxygen while the organism moves to fresh air. Old and complicated function of aerobic metabolism is maintained while new function arises.

 

[dcalling]

Very intesting thought about "as the complexity of an organism increases, the speed of evolution will decrease". When I was still an atheist, one of the thing that puzzles me is if incest give much higher chance of producing tards, how did people in ancient tiny tribs manage to do it?

About a year ago I heard the seminar of a biology professor, and his answer is when we are first created, the genes are prefect so you can incest and it won't matter. As time goes on, people sin/corrupt alone with their genes, that is when you have the problem of DNA matching. And the evidence that Y chromosome is getting shorter help support the creation idea as well.

 

[DogmaHunter]

Another aspect I see being misunderstood lots of times is what exactly constitutes a change to be "bad" or "beneficial". Obviously, some mutations are going to be harmfull under no matter the circumstances. Like if it results in serious deformation or retardation.

Other mutations however, will be determined to be good or bad due to the specific circumstances.

The simplest example is the color of fur.
If you live on the North Pole, you're gonna want to have a white fur.
That same white fur in the jungle however, is not going to help you. In fact, it will turn you into a sitting duck for dangerous predators. If you are a predator yourself, having a fur color that contrasts your surroundings will not exactly help you hunt efficiently.

If you are a predator or a prey, you want to blend with your environment in some sort of "natural camouflage" (unless off course, you have some other trait to compensate for it - but let's leave that aside for now).

So a mutation that produces a white fur will be extremely beneficial in area's with as-good-as permanent snow/ice. The exact same mutation in the jungle or other non-snow/ice area's, will not serve you well. It will make sure that your potential prey or predators out to get you, will spot you from a mile away.

Beneficial/harmfull changes are not limited to physical abilities (like becoming stronger, more flexible, faster, smarter, whatever). It's actually all relative to the environment you find yourself in.

Another great example are moles. They have eyes you know. They don't work anymore. They are actually covered by a thin layer of skin. But the eyeballs and eye sockets are still there. When it moved underground (for whatever reasons), it still had functioning eyes. But living underground for the better part of the day, makes your eyes a very weak spot. With all the dirt and sand down there, these squishy eyeballs are very prone to infection.

So, for the mole, in that environment, it was a series of BENEFICIAL mutations that changed its functioning eyeballs into non-functioning squishy things hidden behind a layer of skin.

Something to keep in mind whenever one speaks about "harmfull" vs "beneficial" mutations.

 

[Split Rock]

Very intesting thought about "as the complexity of an organism increases, the speed of evolution will decrease". When I was still an atheist, one of the thing that puzzles me is if incest give much higher chance of producing tards, how did people in ancient tiny tribs manage to do it?

About a year ago I heard the seminar of a biology professor, and his answer is when we are first created, the genes are prefect so you can incest and it won't matter. As time goes on, people sin/corrupt alone with their genes, that is when you have the problem of DNA matching. And the evidence that Y chromosome is getting shorter help support the creation idea as well.

Can you explain how sin/corruption changes DNA?

 

[DogmaHunter]

Very intesting thought about "as the complexity of an organism increases, the speed of evolution will decrease". When I was still an atheist, one of the thing that puzzles me is if incest give much higher chance of producing tards, how did people in ancient tiny tribs manage to do it?

The tribes weren't as small as you seem to think they were.
Also, jews and muslims are marrying their first and second cousins all the time.

Inbreed is nothing new. Yes, it gives more chances of genetic problems.
And the chances increase the closer related they are. Brother - sister is already quite different from first cousins. Let alone 2nd or 3th cousins.

About a year ago I heard the seminar of a biology professor, and his answer is when we are first created, the genes are prefect so you can incest and it won't matter. As time goes on, people sin/corrupt alone with their genes, that is when you have the problem of DNA matching. And the evidence that Y chromosome is getting shorter help support the creation idea as well.

I see three options:
1. you didn't understand at all what he was saying and are misrepresenting it
2. a very severe case of selective hearing and adding your own imagination
3. the "professor" was lying. Or not really a "professor".

Either way, there is simply no way that a professor in biology worthy of the name would say such a stupid thing and mean it.

 

[digitalgoth]

Very intesting thought about "as the complexity of an organism increases, the speed of evolution will decrease". When I was still an atheist, one of the thing that puzzles me is if incest give much higher chance of producing tards, how did people in ancient tiny tribs manage to do it?

They probably had lots of tards and a high infant mortality rate, which has only recently been arrested because of technological improvements.

Also, and you see this, ironically, in a close ancestor of ours, but chimps also avoid incest naturally, some much so that if you raise make and female chimps together as babies, they won't mate either because they consider themselves related.

And as others have said, once you avoid procreating with your own parents or sibling, the genetic incest issues start to decrease substantially.

About a year ago I heard the seminar of a biology professor, and his answer is when we are first created, the genes are prefect so you can incest and it won't matter. As time goes on, people sin/corrupt alone with their genes, that is when you have the problem of DNA matching. And the evidence that Y chromosome is getting shorter help support the creation idea as well.

I'm not sure when biology professor became preacher, but I have a hard time believing any person educated with biology enough to get a PhD would believe there is ever a "perfect" state that DNA was, that suddenly God caused problems in the DNA copying because Adam blamed his wife for getting bad advice from a talking snake that God put in the garden along with the tree with the fruit that he said not to touch but gave them the ability to sin via bad reptile advice in the first place.

However, I'll bite. It is true you are born with about the "better" DNA you'll have, and through mutations and various processes your DNA can basically "degrade" in the sense that the Telomeres that protect chromosomes can have problems as we age and they turn into the frayed end of a shoelace.

So to speak.

 

[[serious]]

Very intesting thought about "as the complexity of an organism increases, the speed of evolution will decrease". When I was still an atheist, one of the thing that puzzles me is if incest give much higher chance of producing tards, how did people in ancient tiny tribs manage to do it?

About a year ago I heard the seminar of a biology professor, and his answer is when we are first created, the genes are prefect so you can incest and it won't matter. As time goes on, people sin/corrupt alone with their genes, that is when you have the problem of DNA matching. And the evidence that Y chromosome is getting shorter help support the creation idea as well.

Was this a professor of bible-truthines? That sounds nothing like biology.