Natural Selection or Luck

[Micaiah]

I've heard it stated on many occasions that evolution is not random, and things didn't evolve spontaneously by chance. Rather they evolved by a process of natural selection. Is this really the case, or is it essentially luck.

To what extent does natural selection influence the chance of survival of a stable population. Anyone like to try to quantify the improved chances of survival that could result from a beneficial mutation.

 

[notto]

It is estimated that more species have gone extinct than are alive today. Of course when dealing with evolution, "extinction" doesn't mean that ancestors of the extinct species aren't alive today. There is considerable evidence that dinosaurs evolved into birds. So, while the dinosaurs were unsuccessful in their environment, mutation and natural selection provided a way for their genes and kin to live. This is the only way you can meaure success with evolution.

Not sure what kind of statistics you are looking for though.

http://www.gate.net/~rwms/EvoMutations.html
This link outlines beneficial mutations that have been observed in the lab in in a few cases tries to quantify how many mutations are beneficial.

 

[Lanakila]

There is speculation that dinasours evolved into birds. I don't call that considerable evidence. It is something scientists are trying to prove. Explain ocean going mammals in the evolutionary perspective? They don't make sense to me. cause supposedly one celled creatures evolved into eventual fish, which crawled out of the ocean, after they evolved legs, and evolved into higher animals and mammals. When and why did those leg crawling fish evolve into mammals and go back into the oceans. See this is so far fetched it gets downright ridiculous. I know someone will come in with a scientific explanation that loses all us laypeople (non-scientists) but it still is far fetched. I can't believe it, especially after studying just a little about dna and mutations. I can't believe no matter how many billions of years, we could have gotten all the many kinds of animals on this earth through evolution. I am not stupid, but it is so far fetched guys, and so mathmatically impossible. God created the heavens and the earth and all the animals on the earth. In his creation microevolution has happened, obviously and no credible creations denies microevolution. But no matter how many billions of years you try to make the earth, macro evolution creating all these animals is mathamatically impossible.

 

[JohnR7]

Today at 07:04 AM Micaiah said this in Post #1 

To what extent does natural selection influence the chance of survival of a stable population. Anyone like to try to quantify the improved chances of survival that could result from a beneficial mutation.

Today the best chance for survival would be not even to mate two people from the same population. Your best chance for survival would be to mate two people who are geneticly as unlike each other as possible.

 

[Zadok001]

Micaiah:

'Natural Selection' is a mechanism whereby the individuals best suited to reproduce in a specific environment become more populus than those less suited. _Every_ evolutionary change is natural selection.

Mutation does not equal natural selection.

Mutation spread through population due to increased survivability and reproducability does equal natural selection.

You can't really quantify it effectively. I could give you an example using numbers, but it would take a while to calculate.

Lanakila:

Evolution is not a progression. It's not A ==> B ==> C ==> D.

We actually have pretty good fossil records for the evolution of whales. They evolved from a creature similar to a hippo. This hippo-esque critter began spending more and more time in the water during its life cycle, so it adapted more and more to swimming. Eventually, it became unable to return to land.

If you really want to lay it out in a neat little string, it goes Fish ==> Amphibians ==> Reptiles ==> Mammals ==> Hippos ==> Sea-going hippos ==> Whales.

 

[Lanakila]

You think, and scientists propose. But it is still far fetched, and the fossil evidence doesn't prove it happened that way. Scientists interpret very little fossil evidence as evidence of this possiblity. Its all an educated guess, or hypothesis.

 

[notto]

Today at 03:03 PM Lanakila said this in Post #6

You think, and scientists propose. But it is still far fetched, and the fossil evidence doesn't prove it happened that way. Scientists interpret very little fossil evidence as evidence of this possiblity. Its all an educated guess, or hypothesis.

Scientific theories cannot be proven, only falsified. Evolution has yet to be falsified. The evidence in the fossil record is used to piece together the evolution of creatures such as whales. This evidence shows many "whale like" creatures in progression from land mammals to marine mammals. This evidence does not 'prove' that it happened that way and never will but it does support the theory. The evidence supports the "educated guess" so it is not a wild idea that comes out of nowhere.

 

[lucaspa]

Today at 07:04 AM Micaiah said this in Post #1

I've heard it stated on many occasions that evolution is not random, and things didn't evolve spontaneously by chance. Rather they evolved by a process of natural selection. Is this really the case, or is it essentially luck.

To what extent does natural selection influence the chance of survival of a stable population. Anyone like to try to quantify the improved chances of survival that could result from a beneficial mutation.

The discipline of population genetics did the basic mathematical formulas.  Remember that, in the absence of any outside influence, such as natural selection, the frequency of an allele does not change from generation to generation.  That is, if you have a population and 100 and 10 individuals have allele A and 90 have allele a, the next generation will be exactly the same: 10 A and 90 a. This is called the Hardy-Weinberg Law. Frequencies are symbolized mathematically by p and q.  W is the relative fitness value.  So we have W(A), W(B), and W(AB).  The last is the fitness of the heterozygote in a sexually reproducting population. 

So, for the first generation the frequency p of A in the population is: p^2 +2pq + q^2.  Straight Mendelian genetics.

The frequency of p in the next generation after selection is: p' = p^2W(A) + pq W(AB)/p^2W(A) + 2pq W(AB) + q^2 (WB). 

Now, if W(A) and W(AB) are higher than W(B), it can be seen that p' will increase.  Not chance, but pure determinism.

Any other questions, Micaiah?  You can see all this and a lot more in Chapters 4 and 13 in Futuyma's Evolutionary Biology, 1999.

 

[lucaspa]

Today at 09:25 AM Lanakila said this in Post #3]

There is speculation that dinasours evolved into birds. I don't call that considerable evidence.

The evidence is the individual fossils containing both dino and bird features.  Lately, there is also the genetic evidence tying birds to reptiles.  The evidence is considerable.

Explain ocean going mammals in the evolutionary perspective?

Been done.

They don't make sense to me. cause supposedly one celled creatures evolved into eventual fish, which crawled out of the ocean, after they evolved legs, and evolved into higher animals and mammals. When and why did those leg crawling fish evolve into mammals and go back into the oceans.

First, you have the Aristotlean view of evolution as "progression".  That is false. It is simply adaptation to a lifestyle.  Mammals going back to the sea is particularly easy to visualize because of all the intermediate species we see today.  Look at bears like the polar bear that live a lot in water, but retain legs.  They have adaptations to swim better and catch fish and other sea creatures for food. Then look at sea-going otters that have legs but spend nealy all their time in the water.  Now look at seals and sealions.  More adaptations to living in the sea -- loss of back legs -- but still able to clumsily maneuver on land via flippers.  They really only come out of the sea to have young. The final adaptation is being able to give birth in the water.

 I can't believe no matter how many billions of years, we could have gotten all the many kinds of animals on this earth through evolution.

That is the Argument from Personal Incredulity.  You can't believe it so it didn't happen.  Let's take this into the realm of religion.  A lot of people think a virgin having a baby is farfetched and they can't see how it would happen.  But you maintain that it did, don't you?  Don't you also maintain that a person dead for 36 hours came back to life?  Isn't that far-fetched?  After all, we've never seen another instance of it, have we?

God created the heavens and the earth and all the animals on the earth.

Yes, by evolution.

In his creation microevolution has happened, obviously and no credible creations denies microevolution. But no matter how many billions of years you try to make the earth, macro evolution creating all these animals is mathamatically impossible.

Not at all. And we have seen what you call microevolution create new species as we observe them.  Would you like some examples?

 

[Micaiah]

Today at 02:44 AM lucaspa said this in Post #8



The discipline of population genetics did the basic mathematical formulas.  Remember that, in the absence of any outside influence, such as natural selection, the frequency of an allele does not change from generation to generation.  That is, if you have a population and 100 and 10 individuals have allele A and 90 have allele a, the next generation will be exactly the same: 10 A and 90 a. This is called the Hardy-Weinberg Law. Frequencies are symbolized mathematically by p and q.  W is the relative fitness value.  So we have W(A), W(B), and W(AB).  The last is the fitness of the heterozygote in a sexually reproducting population. 

So, for the first generation the frequency p of A in the population is: p^2 +2pq + q^2.  Straight Mendelian genetics.

The frequency of p in the next generation after selection is: p' = p^2W(A) + pq W(AB)/p^2W(A) + 2pq W(AB) + q^2 (WB). 

Now, if W(A) and W(AB) are higher than W(B), it can be seen that p' will increase.  Not chance, but pure determinism.

Any other questions, Micaiah?  You can see all this and a lot more in Chapters 4 and 13 in Futuyma's Evolutionary Biology, 1999.

How do you use this to calculate the increases chances of survival. I am more looking for a percent increase in the chance of something surviving as a result of a beneficial mutation.

 

[notto]

100% if the mutation allows an organism to survive while others in the population die.

 

[lucaspa]

Today at 08:06 PM Micaiah said this in Post #10

How do you use this to calculate the increases chances of survival. I am more looking for a percent increase in the chance of something surviving as a result of a beneficial mutation.

Notto has one answer.  For the individual, the increase in the chance of survival is 100%. For the population, the fitness can be calculated.

Remember Hardy-Weinberg.  The frequency of an allele remains unchanged from generation to generation in the absence of outside influence.  Therefore, the fitness of a new mutation is defined as the ratio of the number of progeny actually produced divided by the number of progeny expected by Mendelian genetics.  This is going to be greater than one in the case of favorable mutations. From that we get a selection coefficient such that fitness = 1 - s.

Now, doing the math we find that the advantageous allele A increases in frequency, per generation, by the amount delta p = (1/2)spq/(1-q).

If you look at the equation, you see that delta p is positive as long as s > 0, even if it is very small.  Eventually p will equal 1, which means that every member of the population will have the allele.  Thus, a characteristic with even a miniscule advantage will be fixed by natural selection.  "Fixed" means every individual will have the allele.

So, as long as a trait is at all, even by the smallest degree, beneficial, then the odds that it will spread to become all the population is 100%.

 

[JohnR7]

Today at 07:21 AM notto said this in Post #2

It is estimated that more species have gone extinct than are alive today.

Of course, didn't you ever hear of the world wide global flood?

 

[Orihalcon]

global flood? no, but i did hear a theory of a meteor hitting 65 million years ago...

 

[Micaiah]

Today at 09:57 AM lucaspa said this in Post #12



Notto has one answer.  For the individual, the increase in the chance of survival is 100%. For the population, the fitness can be calculated.

Remember Hardy-Weinberg.  The frequency of an allele remains unchanged from generation to generation in the absence of outside influence.  Therefore, the fitness of a new mutation is defined as the ratio of the number of progeny actually produced divided by the number of progeny expected by Mendelian genetics.  This is going to be greater than one in the case of favorable mutations. From that we get a selection coefficient such that fitness = 1 - s.

Now, doing the math we find that the advantageous allele A increases in frequency, per generation, by the amount delta p = (1/2)spq/(1-q).

If you look at the equation, you see that delta p is positive as long as s > 0, even if it is very small.  Eventually p will equal 1, which means that every member of the population will have the allele.  Thus, a characteristic with even a miniscule advantage will be fixed by natural selection.  "Fixed" means every individual will have the allele.

So, as long as a trait is at all, even by the smallest degree, beneficial, then the odds that it will spread to become all the population is 100%.

Lets consider a stable population of mammals. Assume the parent gives birth to offspring say five times in their lifetime. Since the population is stable, then only one out of the five will survive. The chance of the animal surviving is then 20%, without any reference to a beneficial mutation.

Can you explain why the chance of an animal surviving with a beneficial mutation in this context is greater than 100%.

 

[Tenek]

Today at 11:20 PM Micaiah said this in Post #15

Lets consider a stable population of mammals. Assume the parent gives birth to offspring say five times in their lifetime. Since the population is stable, then only one out of the five will survive. The chance of the animal surviving is then 20%, without any reference to a beneficial mutation.

Can you explain why the chance of an animal surviving with a beneficial mutation in this context is greater than 100%.

Zero out of five will survive. They all die eventually. The beneficial mutation means that one particular creature has a greater chance of reproducing before its death.

Given a "stable" (now I'd like to find one of those) population, on *average* one of the offspring of a creature will survive to reproduce. A creature with a beneficial mutation might have two of its offspring survive to reproduce. And so on and so forth. This, by the way, destroys the stability of the population.

 

[Micaiah]

How low would the improved chances of survival have to be before we could conclude that natural selection had very little to do with the chance of survival - 50%, 40%, 30% or say 10%.

 

[Orihalcon]

probably 0%. any better chance to reproduce will mean a better chance to reproduce. it probably won't suddenly stand out from the population in a single generation, but given a few, a larger percentage of that population will have the beneficial gene.

anyway, natural selection is based more on chance of reproduction than survival. many spiders have evolved so that the male dies during mating- the reason being that, while the female spider eats the male, he is inseminating her. odd, but i guess nature works out somehow.

 

[Micaiah]

Does any one know the selective values used by applied geneticists in plant and animal trials.

Is evolutionary change supposed to occur only in those situations where the animal would die if the change didn't occur?

 

[chickenman]

survival isn't really the correct definition - you could survive to live 3000 years, if you don't reproduce and pass on your genes, you have a fitness of zero