Evolution: Technically Random?

[drkitten]

So you can predict what species will win?

Yes, and no. Depending upon the time frame that you're looking at, and the details of the prediction.

For example, a new volcanic island out in the middle of the ocean will probably end up colonized by reptiles and birds, but not by mammals. If it is colonized by mammals, they will probably be aquatic mammals like seals or flying ones like bats, buy not terrestrial ones like squirrels. Birds are rolling a large die, in this regard, than mammals, as is demonstrated by the wide variety of bird life (and the number of island groups with almost no native mammals whatsoever, such as Mauritius. (THe only native mammals known on that island group are bats, which of course fly, and dugongs, which are of course aquatic.) This is one reason that so many islands also have native flightless birds, because they can evolve into niches that would "normally" be taken up by mammals. Similarly, the Galapagos islands have local species of bats and seals/sea-lions, but the only other native species is a kind of rice rat. Easter Island has both birds and reptiles, but no native mammals at all. St Helena had native birds, but no mammals (or reptiles).

So given a choice between a random bird species and a random mammal species, I can predict that the bird will win when playing this "let's colonize a new island" game (and history suggests that my choice is pretty accurate, but not perfect). Which is exactly what would be expected if "winning" were random, but strongly biased. I suspect that a founder population of rice rats -- possibly a single pregnant female -- got caught on a log or something and ended up drifting to the Galapagos, in one of those freak one in a zillion chances that happen every so often, but that cannot be relied upon. The chance of a flighted bird being blown of course is much more likely, and thus happens much more often -- and thus we see many more native island birds than native island mammals.

 

[CFLarsen]

Yes, and no. Depending upon the time frame that you're looking at, and the details of the prediction.

For example, a new volcanic island out in the middle of the ocean will probably end up colonized by reptiles and birds, but not by mammals. If it is colonized by mammals, they will probably be aquatic mammals like seals or flying ones like bats, buy not terrestrial ones like squirrels. Birds are rolling a large die, in this regard, than mammals, as is demonstrated by the wide variety of bird life (and the number of island groups with almost no native mammals whatsoever, such as Mauritius. (THe only native mammals known on that island group are bats, which of course fly, and dugongs, which are of course aquatic.) This is one reason that so many islands also have native flightless birds, because they can evolve into niches that would "normally" be taken up by mammals. Similarly, the Galapagos islands have local species of bats and seals/sea-lions, but the only other native species is a kind of rice rat. Easter Island has both birds and reptiles, but no native mammals at all. St Helena had native birds, but no mammals (or reptiles).

So given a choice between a random bird species and a random mammal species, I can predict that the bird will win when playing this "let's colonize a new island" game (and history suggests that my choice is pretty accurate, but not perfect). Which is exactly what would be expected if "winning" were random, but strongly biased. I suspect that a founder population of rice rats -- possibly a single pregnant female -- got caught on a log or something and ended up drifting to the Galapagos, in one of those freak one in a zillion chances that happen every so often, but that cannot be relied upon. The chance of a flighted bird being blown of course is much more likely, and thus happens much more often -- and thus we see many more native island birds than native island mammals.

This is not evolution you are describing. It is migration and colonization.

I am talking about predicting how a specific species evolve. Can you do that?

 

[drkitten]

I am talking about predicting how a specific species evolve. Can you do that?

Not if you keep moving the goalposts around like that, no.

 

[CFLarsen]

Not if you keep moving the goalposts around like that, no.

I asked you if you could. I didn't claim you could.

Can you predict how a specific species will evolve?

 

[drkitten]

I asked you if you could. I didn't claim you could.

Nor did I.

As it happens, I can, for a sufficiently broad prediction. So what?

 

[Melendwyr]

It's certainly possible to make meaningful predictions about how a given species will evolve due to specific selection pressures. With a sufficiently large population, the chance of any particular mutation occurring approaches one.

 

[CFLarsen]

Nor did I.

As it happens, I can, for a sufficiently broad prediction. So what?

Then, your analogy of the dice is invalid.

 

[CFLarsen]

It's certainly possible to make meaningful predictions about how a given species will evolve due to specific selection pressures. With a sufficiently large population, the chance of any particular mutation occurring approaches one.

Give me a concrete example.

 

[Melendwyr]

All domesticated animals. Particularly those bred by animal fanciers.

 

[BillHoyt]

With a sufficiently large population, the chance of any particular mutation occurring approaches one.

I think you mean "expectation" rather than chance. Also, not "all" mutations are possible; not by a long shot.

 

[drkitten]

Then, your analogy of the dice is invalid.

No, because I can also predict the dice for a sufficiently broad prediction. Which does not make the dice any less random.

The central point is just because something is "random" does not mean that it cannot be predicted, for a sufficiently broad prediction. This is where part of the creationist equivocation and ambiguity enters....

 

[Vorticity]

Excuse me, but I have not argued against "random" in the correct (mathematical) usage. I'm arguing against Justin-speak, anticipating his usual nonsense.

OK. I guess there's some history here I'm unaware of.

Are we in agreement then that evolution is indeed random, by the technical definition of the word?

By the way, I notice that Tai used the word "Technically" in the thread title.

I cannot figure what bugs are up Justin's rump. Not being a proctologist, I don't wish to investigate. He has written both aways about science and both ways about evolution. I expect Justin to be Justin.

I still fail to see where he's wrong so far.

I understand that. I am trying to put boundary ropes around the definition of "random" before Justin goes into Justin mode. The bomb goes off. That is predictable. The population genome will shift. That is predictable. I'd recommend you contrast your comments about specific values at specific times with Justin's non-commital about either the overall effect (boom) or the genome shift. When I posed the bomb example, Justin demurred. Justin failed to respond to Pixy Misa, who requested elaboration. Justin ignored Pixy completely. One has to wonder why the points being made seem to elude Justin.

Sure, the bomb will go off and the genome will shift. But that doesn't nail things down completely. Both of those examples describe processes that are manifestly random at the macro level.

 

[Loon]

I don't know if I would offer an opinion on whether evolution is random or not. There are random things going on though.

-Mutation arise randomly (or at least can't be specifically predicted at any level beyond mutation rate).

-The quality of the mutations is random with respect to the environment. This was what separated Darwin from Lamark. Larmark thought that only the necessary mutations would arise. Darwin thought that all sorts of mutations arose and that only the good ones survived.

-The location of mutations is random. Imagine you have a population spread over a varied environment (say the forest extending into the savannah). A mutation arises that causes the organism to blend in really well with the trees. If it arises in the forest, then it has a good chance of spreading because it lets the organism hide from either predators or prey. (It may not spread, though, because the organism may not breed for one reason or another.) If the same mutation arises in an organism living in the savannah, it's not going to help that organism or its offspring survive. The mutation may or may not spread, depending on chance.

Another thing is that evolution is not the same as natural selection. Evolution is the change of gene frequencies over time. There are different ways for this to happen. One is selection. Another is gene flow. Another is drift.

 

[CFLarsen]

All domesticated animals. Particularly those bred by animal fanciers.

That's Intelligent Design.

 

[Vorticity]

This is what you answered to my statement: "But the "weeding out" isn't random":



That must mean that you think at least sometimes "weeding out" is random. If that's not what you meant, fine.

I don't know if the weeding out is random. My point was that it makes no difference to the question of whether or not evolution is random. Evolution is random regardless of whether or not the weeding is random, by virtue of the randomness introduced at the genome level.

 

[Loon]

That's Intelligent Design.

 

[BillHoyt]

OK. I guess there's some history here I'm unaware of.

An understatement.

Are we in agreement then that evolution is indeed random, by the technical definition of the word?

I think so. My summary is that evolution shapes the pdfs, sometimes along the current allelic axes, and sometimes by opening up new probability spaces. My hedging here is simply because of the usual creationist nonsense about "random."

By the way, I notice that Tai used the word "Technically" in the thread title.

Oh, don't worry about. Left to his own devices, he'd find a way to equivocate.

I still fail to see where he's wrong so far.

He's obviously not going to snap at it now, but the part I quoted leaves room for redefining "predictable" and "random".

Sure, the bomb will go off and the genome will shift. But that doesn't nail things down completely. Both of those examples describe processes that are manifestly random at the macro level.

I'm fine with that. Notice, however, T'ai's muttering about the bomb example. I know it takes a Kreskin's Krystal Ball(TM) to see that. I have a dusty one from 1974 I'm willing to part with. Wanna buy it?

 

[CFLarsen]

Hey, it's true....

 

[T'ai Chi]

He wants to move us to accept it, though, by accepting his major premise: that random processes always lead to random results. ... He wants to set up the image of genes in some kind of molecular pogrom that can't possibly lead to evolution.

Bill, please don't put words in my mouth nor impute motives to me.

 

[T'ai Chi]

Very good, then, you've falsified your major premise.

I'm not saying if an organism evolves or not is random, nor am I saying that if a bomb explodes or not is random. I'm saying the output from these processes is random.