Why don't we evolve into microbes?

[Yashbhatt]

We are aware of the term "Survival Of The Fittest by Natural Selection". An organism evolves so that it can survive in its prevailing environment. We know that some microbes are capable of living in the most extreme conditions. Viruses in act can kind of switch between living and non-living. So, why don't other animals including humans evolve into microbes so that we can survive better? Why does the arrow of evolution always point in the direction of complexity? Is it because humans are not exposed to extreme conditions?

 

[D H]

Evolution doesn't have a plan. "Let's see. In 500,000 generations my offspring will need to see or they'll be gobbled up by predators that can see. I better start working on those eye things!" Evolution doesn't work that way. Evolution is a local optimization function. The organisms that produce offspring win. Those that don't lose.

 

[Yashbhatt]

But eventually mutations should help organisms to survive better and humans have advanced so much that instead of adjusting our environment, we try to adjust environment to suit our needs. So, someday we may think, "Hey, being a microbe is cool and helps us survive. ".

 

[Borek]

Why does the arrow of evolution always point in the direction of complexity?

It doesn't.

Some of todays marine filter feeders were in the past freely roaming animals, but later became sessile. Some of the lizards lost their legs to become snakes. Some of the birds lost the ability to fly, same happened to some species of insects inhabiting remote islands. Given the chance of inhabiting a safe niche at the price of losing a costly trait, evolution will choose the former.

"Survival of the fittest" is a tricky term. If "the fittest" means "the one best suited to surviving and reproducing", it is IMHO acceptable (although still doesn't cover all evolutionary processes). If "the fittest" is assumed to mean "the fastest, the strongest" - it is easily ridiculed by counterexamples.

 

[Yashbhatt]

Thanks Borek. I was unaware of organisms becoming less complex.

If any organisms of a certain species are exposed to extreme conditions, then is it possible for them to evolve into microbes?

 

[D H]

If any organisms of a certain species are exposed to extreme conditions, then is it possible for them to evolve into microbes?

By that I assume you mean a complex organism? The answer is no. They die. Or grow thicker fur. Or lose their fur.

There is no evolutionary path from human back to microbe.

 

[Yashbhatt]

There is no evolutionary path from human back to microbe.

But doesn't it seem absurd. Microbes can survive in the harshest of environments. Then, what was the need to evolve into complex organisms?

 

[phinds]

But doesn't it seem absurd. Microbes can survive in the harshest of environments. Then, what was the need to evolve into complex organisms?

What do you think might be the evolutionary path from human to microbe? THAT seems absurd.

 

[Yashbhatt]

What do you think might be the evolutionary path from human to microbe? THAT seems absurd.

I don't mean to say that we should evolve into microbes as I said in the original post. I agree that evolution doesn't have a plan. But evolution should help organisms survive better. So, why not be a virus? Live when you want, become inactive, live again.

But I am not sure about it. do our genes help us evolve directly to the type which suits our environment or do they generate just some random mutations and some of them survive while others die?

 

[ecoo]

But I am not sure about it. do our genes help us evolve directly to the type which suits our environment or do they generate just some random mutations and some of them survive while others die?

Yes, random Gene mutations and environment drives evolution. So let's say a human has a mutation that gives him/her a trait that increases their fitness. They now have a higher chance of survival than those with less fitness and so will have a higher chance to reproduce, and thus, passing on his/her's genes. Over time, this trait may be in most of the population (a change in allele frequency of a certain gene, which is evolution in terms of genes).

Again, if suddenly the environment became hostile to humans, but inhabitable by microbes, then humans would simply die out. Evolution can't say, "Alright, humans are dieing. Time to evolve them to suit the environment by changing them into microbes by giving them a certain gene mutation here and there."

 

[Yashbhatt]

But if the mutations are random, then how come every organism of the same species evolves nearly in the same way? Does one gene of a member say to another of another member : "Hey, this mutation among the random one works. I rate it 5 stars. You should try it!"?

 

[ecoo]

But if the mutations are random, then how come every organism of the same species evolves nearly in the same way? Does one gene of a member say to another of another member : "Hey, this mutation among the random one works. I rate it 5 stars. You should try it!"?

Remember, not all mutations are good. In fact, most mutations are negative. For example, Sickle-cell disease, a genetic disorder, is caused because the people with te disease their hemoglobin gene allele differs by just a little from the normal allele. So negative mutations cause the organism to have a lower fitness and in turn lower chance of survival. So those with less fitness will generally have lower chance to create offspring and those with higher fitness will have a higher chance of surviving.

However, in this day and age, even those (humans) with lower fitness can survive due to technology advances.

It's not that genes are telling each other who is better, it's just that genes that give positive traits will give an organism an advantage in survival and so those without the advantage have a lower chance to create offspring. The same applies to genes that express negative traits.

 

[Chronos]

There is obviously a bias towards intelligence because it has survival value. Smart critters figure out more efficient ways to kill and eat dumb critters. When dumb critters start to lose the survival race, smart critters figure out how to farm them.

 

[ecoo]

There is obviously a bias towards intelligence because it has survival value. Smart critters figure out more efficient ways to kill and eat dumb critters. When dumb critters start to lose the survival race, smart critters figure out how to farm them.

lol farming. Reminds me of the milk industry... :(

 

[Borek]

But if the mutations are random, then how come every organism of the same species evolves nearly in the same way? Does one gene of a member say to another of another member : "Hey, this mutation among the random one works. I rate it 5 stars. You should try it!"?

You don't understand how it works. It is not separate organisms that evolve, it is a population that evolves. Basically mutation occurs once, then it either spreads in the population in the future generations, or not.

 

[Yashbhatt]

@ Borek But isn't that very unlikely. How come all members of a generation have the same mutations when those mutations are random?

 

[Borek]

How come all members of a generation have the same mutations when those mutations are random?

They don't all have the same mutation. Chances are progeny of a member with a particular mutation all have the same mutation. If it is beneficial, they will start to dominate the population in the next generations.

Say, someone has a mutation that makes them twice as intelligent as others. Chances are, their kids will have this mutation as well. If it is beneficial (looking around I doubt, but let's say it is), after several generations their grandgrandkids will be more numerous than kids of their contemporaries, and they will dominate the population.

 

[Yashbhatt]

Who decides if it is beneficial or not?

 

[Borek]

Generally speaking - environment.

Note that "environment" doesn't have to be understood in terms of just geography and ecosystem, just like "the fittest" doesn't necessarily mean "the fastest, the strongest". Environment means also other members of your population.

Also note that it is not that someone "decides". Who "decides" that giraffe can eat leaves from the high trees? Who "decides" that zebra mussel is much more effective at surviving and reproducing in the lakes than many other bivalve species? Who "decided" whether a deer run out or was captured by a tiger? Nobody "decides", it either happens, or not.

There is more to it, but you should have the basic things straight first.

 

[Yashbhatt]

There is more to it, but you should have the basic things straight first.

A lot of people tell me this.

Thanks for the help. I have one more question: Is there any possibility of acquired characteristics being seen in the next generation?

 

[Borek]

Is there any possibility of acquired characteristics being seen in the next generation?

In the context of the evolution and genetics - no.

But in general it depends on what do you mean by acquired and what ways of transmission do you consider. Just because someone trained their biceps doesn't mean their children will have huge biceps as well. But if someone learned hunting they can pass this ability by teaching their kids. I guess that's not what you were thinking about when asking the question, but sometimes the division line between things passed through genetics and through teaching is quite hard to draw.

 

[Ophiolite]

Is there any possibility of acquired characteristics being seen in the next generation?

Simple Answer: No.

Slightly More Complicated Answer: No. When Darwin wrote On The Origin of Species he did not entirely understand the full mechanisms involved in evolution. At times he suspected that some characteristics developed by individuals might be carried forward in some way to the next generation. This was a concept that had been proposed earlier by Lamark. His uncertainty in this regard is apparent in changes made to Origin in the different editions.

By the time Darwin's underlying thesis had been combined with the concepts of population genetics in the Modern Synthesis, inheritance of acquired characteristics was dead and buried.

More Complete, Current Answer:Certain environmental changes that do not directly change the DNA of an individual can, however, produce heritable changes that extend through a number of generations. This is the subject of the field of epigenetics. However, that is not a "full blooded" inheritance of an acquired characteristic, simply the on-going expression - through generations - of a reaction to an environmental impact.

 

[Yashbhatt]

But don't we see children of actors having good acting ability or of singers having good voice?

 

[Ophiolite]

Acting ability likely arises through a combination of inherited and environmental factors. I suspect the proportion involved varies in each individual case.

It is not uncommon for children to wish to pursue the profession of one or other parent, or to be guided (or forced) in this direction by parents. Moreover successful actors have the contacts that help their children get access to opportunities other lack.

I suspect singing has a much stronger genetic component, related to various aspects of physiology. Therefore it is not surprising that a good singer, who has the genetic coding that gives them the physiology for good singing, would have children who inherited these same genes and thus the ability to be a good singer.

So, none of this is surprising and is wholly consistent with my Simple Answer given above. i.e. we do not inherit acquired characteristics.

 

[Yashbhatt]

And that "singing gene" is a result of random mutations?

 

[ecoo]

And that "singing gene" is a result of random mutations?

Voice has to do with vocal cords, mouth size, breathing, etc. So people with higher pitch voices who can go higher have genes that work in favor of singing. Those with these genes just happen to survive and pass their genes down. So singers who have these genes that favor singing pass it down to their children.

So yes, the random gene mutations that gave bigger/smaller vocal cords survived and those who have these genes may have the potential to sing clearer, at a higher pitch, etc.

 

[AlephZero]

But don't we see children of actors having good acting ability or of singers having good voice?

There could be a completely different explanation.

Suppose that "acting" or "singing" doesn't require any special talents at all. Anybody can do it, but there is only work for a small number of actors and singers, so most people choose a different career. If you try to become a professional actor or singer, you need to get lucky to find work.

In that case, it should be obvious that children of actors or singers will have more chance of "getting lucky" than the rest of the population, because of the people their parents know.

I'm not saying that hypothesis is true, but if you want to claim that acting and singing ability is inherited, you need to show that it is false!

Actually there is some empirical evidence that no "special ability" is required for western classical music, beyond having the opportunity to learn. For example see http://en.wikipedia.org/wiki/El_Sistema. But that reference is far too US-centered - it ignores similar projects in the Middle East, South Africa, etc, and the huge growth of western music performance in China (for example the Pearl River Piano Company is the largest piano manufacturer in the world, and the number of piano students in China is estimated at between 30 and 80 million).

 

[Yashbhatt]

Voice has to do with vocal cords, mouth size, breathing, etc. So people with higher pitch voices who can go higher have genes that work in favor of singing. Those with these genes just happen to survive and pass their genes down. So singers who have these genes that favor singing pass it down to their children.

So yes, the random gene mutations that gave bigger/smaller vocal cords survived and those who have these genes may have the potential to sing clearer, at a higher pitch, etc.

Why did those mutations survive? Singing does not help in adapting to the environment.

 

[ecoo]

Why did those mutations survive? Singing does not help in adapting to the environment.

Could be just luck, since the mutations don't exactly decrease fitness nor increase it.

However, let's not forget that a 'nice" voice is relative (e.g. low or high pitch, thin or vibrant). So there isn't set traits that make a voice sound better. However, say that men generally like girls with higher pitched voices. Then those girls with a higher pitched voice have an evolutionary advantage over those with a lower pitched voice (men are attracted to higher pitch and have a higher chance to reproduce with the girls with high pitch). Later in the path of time, suddenly most girls in the general population have a higher pitched voice.

 

[SteamKing]

Why did those mutations survive? Singing does not help in adapting to the environment.

Not everything you are capable of doing necessarily provides better adaptation to your environment.

The ability to sing well may just reflect an individual with superior control of the muscles involved in speech (and consequently breathing). So to for the musician, these are individuals who exhibit superior hand-eye coordination, or control of the muscles involved in breathing. These are characteristics which also might enable an individual a better chance at survival, other things being equal, but because we don't have to wrestle our breakfast away from a cheetah every morning, we can use these qualities for other pursuits.

 

[Ophiolite]

Why did those mutations survive? Singing does not help in adapting to the environment.

Really? You don't think the winner of Pop Idol, or the X-Factor lack success in finding mates?

 

[Ryan_m_b]

Why did those mutations survive? Singing does not help in adapting to the environment.

You're only considering natural selection but sexual selection is a powerful force for evolution too. If a trait enhances an organisms ability to reproduce then it will pass on it's genes more than others. There's no "singing" gene but the combination of genes that give one a propensity to sing well could make it easier for an individual to reproduce. A real world example of this would be birds, some of which have evolved very complex mating calls.

As for why humans don't evolve into bacteria: it's possible there is a very, very long series of adaptations that lead to that but each individual stage would have to confer a selective advantage. This is unlikely.

 

[Yashbhatt]

Okay okay I get it now.

 

[SteamKing]

Usually, organisms don't evolve into a niche where there is already plenty of competition. Microbes have held their niche for about 3.5 billion years already, so they seem adapted well enough to compete with just about anything that comes along, with much disadvantage to the newcomer.

After all, humans have tried to exterminate/eliminate disease carrying microbes actively for a little over a century now. We won some impressive early victories with the development of artificial antibiotics (like penicillin, et seq.), but now the pendulum is swinging back into the microbes' favor since the microbes which survived the antibiotic onslaught have produced antibiotic-resistant strains which are rendering our medical arsenals pitifully ineffective. Having large scale outbreaks of infections return is not an exciting prospect for humanity, especially those in the developed world who have grown accustomed to antibiotic treatment providing quick and effective cures for such illnesses.

 

[Yashbhatt]

Usually, organisms don't evolve into a niche where there is already plenty of competition. Microbes have held their niche for about 3.5 billion years already, so they seem adapted well enough to compete with just about anything that comes along, with much disadvantage to the newcomer.

After all, humans have tried to exterminate/eliminate disease carrying microbes actively for a little over a century now. We won some impressive early victories with the development of artificial antibiotics (like penicillin, et seq.), but now the pendulum is swinging back into the microbes' favor since the microbes which survived the antibiotic onslaught have produced antibiotic-resistant strains which are rendering our medical arsenals pitifully ineffective. Having large scale outbreaks of infections return is not an exciting prospect for humanity, especially those in the developed world who have grown accustomed to antibiotic treatment providing quick and effective cures for such illnesses.

That is the reason I thought that being a microbe is better as one can adapt very quickly to the environment. (For example, the common cold virus).

 

[ecoo]

That is the reason I thought that being a microbe is better as one can adapt very quickly to the environment. (For example, the common cold virus).

It may be "better" in your terms, but the tree of life branches off to many different directions.
Microbes have survived for a long time, but I believe so can humans. Us Homo sapiens are pretty new compared to microbes.

We're already humans and not microbes, so let's be happy about that. :D

 

[Yashbhatt]

Sure we can survive. But humans generally don't adapt themselves to the environment but rather change it.

 

[SteamKing]

Sure we can survive. But humans generally don't adapt themselves to the environment but rather change it.

You can't really say that since adaptations take many generations to develop and produce individuals which are noticeably different because of such adaptation. In humans, a generation is generally reckoned to be about 20 years, and fewer than 10 generations have elapsed since genetics was recognized as a science, much too short a time for significant adaptation to become apparent.

Humans have been adapting to their environment since Day 1, as can be seen by the variety of fossil humans discovered over the last century and a half. H. erectus isn't just an older version of the modern H. sapiens, but quite a different creature altogether. Certainly, if you saw a live specimen of H. erectus walking down a street, you would have no trouble discerning that this individual is not the same as other humans, just shorter and stockier.

 

[Ryan_m_b]

That is the reason I thought that being a microbe is better as one can adapt very quickly to the environment. (For example, the common cold virus).

Evolution doesn't work by deciding on the best possible adaptation to an environment and then changing a species into that. If an organism has traits that enable it to reproduce more than others then that trait will dominate. It's not about the bets possible configuration, it's about survival.

Also as an aside microorganisms are well adapted to their environment which is very different to human environments.

Sure we can survive. But humans generally don't adapt themselves to the environment but rather change it.

Organisms don't adapt themselves either in an evolutionary sense, species do. It's an interesting discussion to what extent natural selection has been curtailed in humans but we still experience sexual selection, genetic drift and gene flow. Or to put it another way there are many processes by which evolution occurs other than natural selection.

 

[Yashbhatt]

Let us take some example. Consider some vestigial organ like say appendix or tails. As they were not required anymore as humans evolved, they dormant and smaller in size. So, if humans evolved by random mutations as described before in this thread, then how come all these random mutations act towards eliminating a particular organ? I have mentioned this before but I can't understand it.

 

[Ryan_m_b]

Let us take some example. Consider some vestigial organ like say appendix or tails. As they were not required anymore as humans evolved, they dormant and smaller in size. So, if humans evolved by random mutations as described before in this thread, then how come all these random mutations act towards eliminating a particular organ? I have mentioned this before but I can't understand it.

Mutations can be negative, neutral or positive. Negative mutations decrease the chances of reproduction, neutral have no effect and positive increases the chances. If a mutation is positive then over time (how long depends on how positive it is aka weak or strong) it will proliferate through the species as organisms with the mutation reproduce more.

Whether or not a mutation is negative, neutral or positive is mostly down to the environment which provides context. It's the environment which determines what mutations will spread, e.g. A mutation that makes an organism red in colour will increase its chance of survival if it is in a red environment so it can be camouflaged. The appendix, along with most vestigial organs, could decrease in size and eventually disappear as they cost energy to produce and maintain which is a waste. But if the amount of energy wasted is negligible then it's not going to effect reproduction and so they'll stick around unless some other factor arises.

 

[bobze]

Let us take some example. Consider some vestigial organ like say appendix or tails. As they were not required anymore as humans evolved, they dormant and smaller in size. So, if humans evolved by random mutations as described before in this thread, then how come all these random mutations act towards eliminating a particular organ? I have mentioned this before but I can't understand it.

Tails aren't free to make. Think about it from a cost-benefit analysis.

 

[thorium1010]

Let us take some example. Consider some vestigial organ like say appendix or tails. As they were not required anymore as humans evolved, they dormant and smaller in size. So, if humans evolved by random mutations as described before in this thread, then how come all these random mutations act towards eliminating a particular organ? I have mentioned this before but I can't understand it.

Think of it another way , analogy like a person who hits the gym to build muscle size, does it frequently and will increase his muscle size. But once he stops it it will return to previous size , before he started his training.

It may not be a good analogy , but extend this over long periods of time , where the populations of a species has no more use for the particular organ , body tries to conserve energy over that period of time by simply eliminating or decreasing its size.

 

[Yashbhatt]

Now I get it. Thanks for explaining guys.

 

[Ygggdrasil]

Let us take some example. Consider some vestigial organ like say appendix or tails. As they were not required anymore as humans evolved, they dormant and smaller in size. So, if humans evolved by random mutations as described before in this thread, then how come all these random mutations act towards eliminating a particular organ? I have mentioned this before but I can't understand it.

There's also the fact that it is easier to break something (a loss of function) than to improve something (a gain of function). Thus, if a certain function is not required, over time random mutations will tend to degrade the function.

 

[Hornbein]

Why does the arrow of evolution always point in the direction of complexity?

It's a good question. It doesn't always, but that is the general trend. It is possible that in the future things will reverse, if conditions change to favor it.

In the past one hundred years popular music and other entertainments have evolved to be much simpler.

 

[Yashbhatt]

Really? You don't think the winner of Pop Idol, or the X-Factor lack success in finding mates?

If it's all about reproducing, then there shouldn't exist any people with low sex drive by now, should they?

 

[Borek]

If it's all about reproducing, then there shouldn't exist any people with low sex drive by now, should they?

1. Just because they don't leave progeny doesn't mean similar combination of genes are impossible in the next generations. Compare with hemophilia.

2. In the case of men that's more complicated, but in the case of women it is perfectly possible to be completely passive, have sex just because of the social obligations, and leave progeny despite having no sex drive at all.

These things never want to be simple (which is why they are fascinating to research; sadly, they look simple, so people think they understand them, but then they find something that doesn't fit and they are sure they just falsified the whole idea).

 

[Yashbhatt]

1. Just because they don't leave progeny doesn't mean similar combination of genes are impossible in the next generations. Compare with hemophilia.

2. In the case of men that's more complicated, but in the case of women it is perfectly possible to be completely passive, have sex just because of the social obligations, and leave progeny despite having no sex drive at all.

These things never want to be simple (which is why they are fascinating to research; sadly, they look simple, so people think they understand them, but then they find something that doesn't fit and they are sure they just falsified the whole idea).

What you mentioned is correct but a person with more sex drive tends to mate often and produce more offsprings. So, isn't that a survival advantage?

 

[Ryan_m_b]

What you mentioned is correct but a person with more sex drive tends to mate often and produce more offsprings. So, isn't that a survival advantage?

Things are rarely so clear cut. For starters libido might not even be strongly inherited, in which case it would not experience a strong selective pressure. Whether or not one has a high or low libido might be primarily down to environmental factors which either have a long term effect (i.e. they caused a lasting change at some point in your development) or could be transient (i.e. job stress). It's also extremely likely that sexuality and sex drive are the phenotypic result of a huge range of genetic factors (as well as the aforementioned environmental). The capacity for sex drive could be inherited but not necessarily a specific level.

Even if libido was strongly inherited there are possibilities for why it might be a disadvantage. The hormonal differences between high and low libido people might be detrimental to health meaning that in the long term less offspring are produced. I'm not saying that's true, just offering it as an example of how you have to consider a range of scenarios.