Why don't we evolve into microbes?

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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?
 

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  • #2
D H
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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.
 
  • #3
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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. ".
 
  • #4
Borek
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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.
 
  • #5
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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?
 
  • #6
D H
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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.
 
  • #7
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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?
 
  • #8
phinds
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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.
 
  • #9
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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?
 
  • #10
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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."
 
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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!"?
 
  • #12
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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 eachother 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.
 
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  • #13
Chronos
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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.
 
  • #14
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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.... :(
 
  • #15
Borek
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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.
 
  • #16
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@ Borek But isn't that very unlikely. How come all members of a generation have the same mutations when those mutations are random?
 
  • #17
Borek
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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.
 
  • #18
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Who decides if it is beneficial or not?
 
  • #19
Borek
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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.
 
  • #20
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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?
 
  • #21
Borek
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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.
 
  • #22
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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.
 
  • #23
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But don't we see children of actors having good acting ability or of singers having good voice?
 
  • #24
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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.
 
  • #25
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And that "singing gene" is a result of random mutations?
 

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