Questions of Natural selection

[Confused]

At the end of Why Darwin Matters: A case against intelligent design, the author, Shermer, raises some interesting issues with Natural Selection. These will naturally be the issues for debate:

1) If natural selection is the primary mechanism of evolution, what is the role of chance and contingency in the history of life?

2) What is the target of Natural Selection: the individual organism; or the lower levels of genes, chromosomes, organelles, and cells; or the higher level of groups, species, etc.. Why?

[honegod]

There also could be random variation that is neither selected for or against, until there is a change in the environment. The variations are also 'evoultion" (change of the frequency of allese over generatoins), but not nessesarily due to environmental selection.

that is why individuals within a species are different, establishing a pool of variation so that there is a range of choices to be selected through.

I think the whole "species" thing is a make believe catigorization we invented to simplify things. so we can look horizontally at a broad snapshot instead of vertically at the growth line of each individual line of succession.

it's handy, but misleading.

[Goat]

There also could be random variation that is neither selected for or against, until there is a change in the environment. The variations are also 'evoultion" (change of the frequency of allese over generatoins), but not nessesarily due to environmental selection.

that is why individuals within a species are different, establishing a pool of variation so that there is a range of choices to be selected through.

I think the whole "species" thing is a make believe catigorization we invented to simplify things. so we can look horizontally at a broad snapshot instead of vertically at the growth line of each individual line of succession.

it's handy, but misleading.

On the contrary. while some of the boarder lines is blurred, there are very good reasons for the taxonomy of species.

The bonobo is not the a chimp. A horse is not a donkey.

[Cathar1950]

There also could be random variation that is neither selected for or against, until there is a change in the environment. The variations are also 'evoultion" (change of the frequency of allese over generatoins), but not nessesarily due to environmental selection.

that is why individuals within a species are different, establishing a pool of variation so that there is a range of choices to be selected through.

I think the whole "species" thing is a make believe catigorization we invented to simplify things. so we can look horizontally at a broad snapshot instead of vertically at the growth line of each individual line of succession.

it's handy, but misleading.

On the contrary. while some of the boarder lines is blurred, there are very good reasons for the taxonomy of species.

The bonobo is not the a chimp. A horse is not a donkey.

They also have been seperated as a population that didn't intereact with other populations. If there were constant breeding between populations we would all look the same after a half billion years what ever that creature would be.
It gives me the willies.

[Cephus]

Possibly the next step we see in our evolution will have to do with the lungs, thanks to all the chemistry we place into the air. Watch for it int he next 2-3 generations.

It's unlikely that you'll see any large-scale changes in humanity any time soon, simply because evolution is a response to change in the natural environment and now that mankind can manipulate his environment, there isn't much call for change.

Regardless, you virtually never see any form of significant change, particularly positive change, in just a few generations.

[honegod]

it's handy, but misleading.

On the contrary. while some of the boarder lines is blurred, there are very good reasons for the taxonomy of species.

the main misleading bit that I was thinking of is that it makes us assume that 'species' as a inability to breed across the 'boundry' applies universally backward through time.

where that inability to crossbreed might well be a fairly recent innovation.

the 'cambrian explosion' would make more sense if pretty much everything could interbreed, that would explain the wild diversity and the rapid diversification.

[Cephus]

the 'cambrian explosion' would make more sense if pretty much everything could interbreed, that would explain the wild diversity and the rapid diversification.

I think it's more a matter of life suddenly existing and there being a wide variety of uninhabited ecological niches available to be filled. You would get an 'explosion' of life, simply because there was such massive opportunity for life to flourish and grow.

No real mystery there.

[ST88]

Ok, I grasp what you are saying now. But in your scenario, you are presenting a case in which evolution preceded selection then, or am I misunderstanding your scenario. If the production of the appendix serves no purpose now, but may in the future, then are we not saying that evolution predicts selection to degree or that natural selection is by chance noting the subtle changes in the environment that perhaps we aren't cognizant of yet, and adapting the body slowly for the eventuality it percieves is coming? In such a case, it wouldn't be natural, or random, but rather it would be guided by the environment in which we live.

Perhaps I am not grasping what you are saying. Perhaps 20 hours of sleep didn't clear the confusion as I had hoped.

goat gave the correct response here, but let me just add that there may be some confusion here about what is random and what is directed. The mutation is random - it could lead to anything: no appendix, multiple appendices, an appendix that looked like Ernest Borgnine, etc. The environment is the set of constraints (again, somewhat random) that essentially will allow a mutation to survive into the next generation or no. The head-thorax-abdomen body paradigm has been fairly successful for animals, and that is in large part because the environment rewards such a structure. It should be noted that nothing perceives that a change is coming -- the changes themselves are random. In an ice age, all tropical animals die. In a global warming scenario, all arctic animals die. So that much might be said to be "guided", but a more appropriate way of thinking about it would be "constraints", because there are a number of ways to succeed in any given environment -- both the shark and the dolphin survive in the ocean despite having wildly different genotypes.

[Confused]

Ok, I grasp what you are saying now. But in your scenario, you are presenting a case in which evolution preceded selection then, or am I misunderstanding your scenario. If the production of the appendix serves no purpose now, but may in the future, then are we not saying that evolution predicts selection to degree or that natural selection is by chance noting the subtle changes in the environment that perhaps we aren't cognizant of yet, and adapting the body slowly for the eventuality it percieves is coming? In such a case, it wouldn't be natural, or random, but rather it would be guided by the environment in which we live.

Perhaps I am not grasping what you are saying. Perhaps 20 hours of sleep didn't clear the confusion as I had hoped.

goat gave the correct response here, but let me just add that there may be some confusion here about what is random and what is directed. The mutation is random - it could lead to anything: no appendix, multiple appendices, an appendix that looked like Ernest Borgnine, etc. The environment is the set of constraints (again, somewhat random) that essentially will allow a mutation to survive into the next generation or no. The head-thorax-abdomen body paradigm has been fairly successful for animals, and that is in large part because the environment rewards such a structure. It should be noted that nothing perceives that a change is coming -- the changes themselves are random. In an ice age, all tropical animals die. In a global warming scenario, all arctic animals die. So that much might be said to be "guided", but a more appropriate way of thinking about it would be "constraints", because there are a number of ways to succeed in any given environment -- both the shark and the dolphin survive in the ocean despite having wildly different genotypes.

I grasped it from Goat, but thanks for the additional clarification.

[honegod]

Posted: Tue Mar 13, 2007

the main misleading bit that I was thinking of is that it makes us assume that 'species' as a inability to breed across the 'boundry' applies universally backward through time.

http://news.nationalgeographic.com/news ... ][b]070314[/b][/i][/u]-hybrids.html

http://news.nationalgeographic.com/news ... brids.html

Interspecies Sex: Evolution's Hidden Secret?

heh, I beat them by a day

[jjg]

Natural selection just keeps a species healthy. Random mutation and gene drift are the mechanisms of evolution.