Question about Darwin's evolution

[issacnewton]

Hi

This is the first time I am posting in Biology forum. I didn't study any biology after grade 10. But I always found it fascinating. So I have a question about the theory of evolution.
Now as I understand it, theory says that the parts of human body, or the behavior tend to get discarded if there is no need of it. So what about the irrational behavior in humans. Has irrational behavior helped us survive. We generally discourage irrational behavior and encourage rational. So in the evolution of our species, why the irrational has survived till today ?
Does it help human survival in some way ?

Thanks

 

[Pythagorean]

What do you define as irrational behavior?

With examples please.

 

[jackmell]

Maybe the OP could start by considering a "poor judgment" trait in a population. But what does even that mean? I suppose perhaps a decision which does not contribute in a positive way to the survival or reproductive success of the individual. But some of those apparently poor judgments could be mistaken for "risk" and sometimes risk has an advantage: two men, one smaller than the other, compete for a mate. The smaller is obviously at a disadvantage but if he risks the confrontation with such an apparently poor decision, the payoff would be substantial: he would contribute his willingness to risk, to risk life to acquire food, to risk his health to protect his mate and children, to risk taking chances that would bring success to his lineage, he would be contributing that trait to his successors and in those ways, it would be a fit trait.

Also, keep in mind that a good survival strategy for a population is to have a very diverse set of traits in it's genotype, not all of which may be beneficial at one time. This is to ensure if the environment changes suddenly, traits which were before beneficial may no longer be but with a diverse set of traits, there is a chance that traits before which were not fit, now are suddenly fit. An ecosystem example of this is a forest with many species of plants. This affords a good buffer to a dramatic change in environment such as a new bacterial which destroys all the oak trees. If the forest were filled with just (or majority of) oak trees, this sudden change in environment could push this ecosystem past a critical point whereby it could not recover with a grass-land replacing it. But a forest with many species has a much better chance that some of the species are not susceptible to the bacteria preventing the overall ecosystem from reaching this critical point of no return. And what goes for the ecosystem, I think could be applied to a single population: take America with it's over-abundance of food. Overweight is a poor trait. But if the environment suddenly changed and food were scarce, having reserve fat on your body (to some degree) would be an advantageous trait.

. . . . still very much a matter of dynamics isn't it Geometer?

 

[issacnewton]

Well, to give an example of irrational behavior would be religious extremists. Why does this
trait survive after so many years of evolution.

Another example would be general stubbornness of some people to refuse to change their views in the light of new evidence. Attachment to some dogma with no evidence .
This is what I meant by irrational behavior

 

[NobodySpecial]

Well, to give an example of irrational behavior would be religious extremists. Why does this trait survive after so many years of evolution.

Because they have more offspring and pass this trait onto them.

Remember evolution isn't aiming for anything better/more advanced/more evolved - it's just each gene aiming for more copies of itself.

 

[jackmell]

Well, to give an example of irrational behavior would be religious extremists. Why does this
trait survive after so many years of evolution.

Alright, that's a problem right there. Evolution works in millions of years or at least many thousands of years so that second sentence is ill-posed: a few thousand years of human culture is not enough time to make a significant dent in the frequency of this trait in the population.

And another thing. Keep in mind that evolution is all about survival and reproductive success. How does courage to risk life enter into that equation?

 

[Pythagorean]

I don't think this kind of behavior is particularly threatening to their survivability.

 

[Pythagorean]

Maybe the OP could start by considering a "poor judgment" trait in a population. But what does even that mean? I suppose perhaps a decision which does not contribute in a positive way to the survival or reproductive success of the individual. But some of those apparently poor judgments could be mistaken for "risk" and sometimes risk has an advantage: two men, one smaller than the other, compete for a mate. The smaller is obviously at a disadvantage but if he risks the confrontation with such an apparently poor decision, the payoff would be substantial: he would contribute his willingness to risk, to risk life to acquire food, to risk his health to protect his mate and children, to risk taking chances that would bring success to his lineage, he would be contributing that trait to his successors and in those ways, it would be a fit trait.

Also, keep in mind that a good survival strategy for a population is to have a very diverse set of traits in it's genotype, not all of which may be beneficial at one time. This is to ensure if the environment changes suddenly, traits which were before beneficial may no longer be but with a diverse set of traits, there is a chance that traits before which were not fit, now are suddenly fit. An ecosystem example of this is a forest with many species of plants. This affords a good buffer to a dramatic change in environment such as a new bacterial which destroys all the oak trees. If the forest were filled with just (or majority of) oak trees, this sudden change in environment could push this ecosystem past a critical point whereby it could not recover with a grass-land replacing it. But a forest with many species has a much better chance that some of the species are not susceptible to the bacteria preventing the overall ecosystem from reaching this critical point of no return. And what goes for the ecosystem, I think could be applied to a single population: take America with it's over-abundance of food. Overweight is a poor trait. But if the environment suddenly changed and food were scarce, having reserve fat on your body (to some degree) would be an advantageous trait.

. . . . still very much a matter of dynamics isn't it Geometer?

I would say yes, naturally.

Though, I think most irrational behavior as the OP means it is not really a Darwinian thing in the evolutionary sense. Perhaps in the survivability of trends in behavioral norms and social tolerance, where a bunch of different subcultures are competing and certain subcultures win out and become the norm over time while others die off. Each of the subcultures may equivalently view other subcultures as having the irrational behavior, but the dominant consensus of "rational behavior" evolves out of and influences these smaller cliques.

 

[jackmell]

I would say yes, naturally.

Though, I think most irrational behavior as the OP means it is not really a Darwinian thing in the evolutionary sense. Perhaps in the survivability of trends in behavioral norms and social tolerance, where a bunch of different subcultures are competing and certain subcultures win out and become the norm over time while others die off. Each of the subcultures may equivalently view other subcultures as having the irrational behavior, but the dominant consensus of "rational behavior" evolves out of and influences these smaller cliques.

Yeah, I like that. Thank you. :)

 

[issacnewton]

interesting discussion. Now I get it. So irrational behavior may actually help the survivability of the species. that makes sense.

 

[Ken Natton]

...as I understand it, theory says that the parts of human body, or the behavior tend to get discarded if there is no need of it.

That is not quite what the theory says, as I understand it. Certainly, if there is no selective advantage to a particular genetic trait, then natural selection cannot operate to preserve that feature. So mutations to the genes involved in the provision of that trait will not be selected against, and, over time, the trait may atrophy. That is not the same as saying it is discarded. A fine example of this is our sense of smell. No one would suggest that our ancestors ever had the sensitivity to smell that dogs have, but we did used to have a much more acute sense of smell than we do now. It certainly did have a very powerful selective advantage and was thus highly developed and long preserved. But then we developed trichromatic vision. The selective advantage offered by trichromatic vision must have been quite separate from the selective advantage that was acting to preserve our sense of smell. But having developed it, trichromatic vision proved to be a much more effective protection against the same things that we had previously relied on our sense of smell for. Thus, natural selection was no longer able to act to select against mutations to the genes that gave us our sense of smell, and so it has atrophied. That doesn’t mean that we have discarded it all together. Only that it is not as sensitive as it was.

Behaviours are a whole further level of complexity in terms of genetic programming. Let me only say that I don’t think one needs to look for some Darwinian explanation for irrational behaviour. I am not convinced that such behaviour has any origin in our genes.

 

[DBTS]

Jackmell stated, "I suppose perhaps a decision which does not contribute in a positive way to the survival or reproductive success of the individual," would be something I agree with to an extent. I would expound upon it by saying, individuals act in accordance to what is the best solution for them. In terms of extremists, they are still acting in the notion of what is best for their "species" or people as a whole. Of course, with every decision made, there are those that believe it is not a good decision. Therefore, it is irrational. I say irrationality only exists in the sense of human perception, not in the actual existence of the universal laws or physical for that matter.

 

[Lievo]

Now as I understand it, theory says that the parts of human body, or the behavior tend to get discarded if there is no need of it.

In fact, this is not correct. Theory says that the behaviors that increase the fitness will get selected, and that's not the same as saying that neutral mutation will get discarded. In fact, it's quite easy to compute the theoretical prediction that neutral mutation will get discarded only after a very long time, likely longer than the species lifetime. For more on these questions see this http://en.wikipedia.org/wiki/Neutral_theory_of_molecular_evolution" .

 

[hansvi]

Well, to give an example of irrational behavior would be religious extremists. Why does this
trait survive after so many years of evolution.

That is an idea, and is unrelated to genes. Although the spreading of these ideas can be compared to evolution, it is not the same thing. Richard Dawkins coined the term memetics for this. What makes you a fundamentalist is not dependant on your genes.

More in general, why people are prone to fall for utter nonsense, is maybe just a misfiring, we constantly see patterns. If you are just randomly lucky one day, you may realize that the last time you were this lucky you wore the same socks. Therefore, it must be the socks that causes all this luck! And voila, a new superstition is born. Because the ability to recognize real patterns is so beneficial, its failure when presented with random data might simply be worth it.

There are many answers to a general question like this one. Another example is the gullability of children. Small children believe everything you say, this is beneficial because they will listen to their parents who have way more experience than them (don't go near the water, don't eat those berries). This wears of as they get older, but how much depends from person to person, I suppose.

 

[issacnewton]

I understood it now. Thank you to everybody who participated. The question was bugging me for some time