Why don't we evolve into microbes?

  1. 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?
     
  2. jcsd
  3. D H

    Staff: Mentor

    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.
     
  4. 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. ".
     
  5. Borek

    Staff: Mentor

    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.
     
  6. 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?
     
  7. D H

    Staff: Mentor

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

    phinds 8,122
    Gold Member

    What do you think might be the evolutionary path from human to microbe? THAT seems absurd.
     
  10. 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?
     
  11. 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."
     
    Last edited: May 16, 2014
  12. 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!"?
     
  13. 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.
     
    Last edited: May 17, 2014
  14. Chronos

    Chronos 9,784
    Science Advisor
    Gold Member

    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.
     
  15. lol farming. Reminds me of the milk industry.... :(
     
  16. Borek

    Staff: Mentor

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

    Staff: Mentor

    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.
     
  19. Who decides if it is beneficial or not?
     
  20. Borek

    Staff: Mentor

    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.
     
  21. 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?
     
Know someone interested in this topic? Share a link to this question via email, Google+, Twitter, or Facebook

0
Draft saved Draft deleted