copernicus

You still made no suggestion. You asked a question. My answer was that you can't possibly know what was probable without understanding all of the selectional outcomes that led to a particular evolutionary factors over time. However, if you want to understand the evolution of the eye--a question that was first raised by Paley 200 years ago in his so-called "watchmaker" argument--you need to pay some attention to the answers that have already been given to Paley's argument. The Blind Watchmaker is a devastating reply to Paley's Argument from Personal Incredulity. This is an old argument, and you are not bringing it up for the first time in this forum. For example, see: <a href="http://www.2think.org/eye.shtml" target="_blank">http://www.2think.org/eye.shtml</a> and <a href="http://www.rennard.org/alife/english/biomintrgb.html" target="_blank">http://www.rennard.org/alife/english/biomintrgb.html</a> . If you are going to raise these old conundrums, then please don't act as if none of us had ever heard them before. There is an extensive literature on the subject.

[ April 06, 2002: Message edited by: copernicus ]</p>

RufusAtticus

You might not be, but there are plenty of scientists and experienced laymen on this board willing to help you.

-RvFvS

unworthyone

How was he able to do it with the plants?

And the other mumbo-jumbo, I have no idea what you are talking about, personal incredulity etc...

Never heard of it.

Maybe I should change the probability question to something more easily figured like....

The chances of life to evolve from non-living? (protein stuff, you know?)

[ April 06, 2002: Message edited by: unworthyone ]</p>

Quetzal

Hi unworthyone. I'd like to try and answer your opening post. It seems to me that we've gotten somewhat sidetracked - after all, it's impossible to dive into specific examples of how a particular thing evolved without a basic understanding of what we're talking about inre random mutation and natural selection.

You posted: That's a great question, and a lot of the subsequent posts show a basic misunderstanding. (apologies to the II regulars who've seen me post this before - you know how much I like recycling old rhetoric. )

First off, there are some very basic statements that, for evolution to be true, must be true. All provide potential pathways for falsification. All lend themselves to development of testable hypotheses. All have (scientifically) predictive value:

1. If all the offspring that organisms can produce were to survive and reproduce, they would soon overrun the earth.

2. As a consequence, there is competition to survive and reproduce, in which only a few individuals succeed in leaving progeny.

3. Organisms show variation in characteristics or traits that influence their success in this struggle for existence. Individuals within a population vary from one another in many traits.

4. Offspring tend to resemble parents, including in characters that influence success in the struggle to survive and reproduce.

5. Parents possessing certain traits that enable them to survive and reproduce will contribute disproportionately to the offspring that make up the next generation.

6. To the extent that offspring resemble their parents, the population in the next generation will consist of a higher proportion of individuals that possess whatever adaptation enabled their parents to survive and reproduce.

Next, you need to understand (and remember) that natural selection leading to evolution is simply the differential reproduction of genotypes. There are two basic assumptions for natural selection to work:

1. There must be heritable variation for some trait. Examples: beak size, color pattern, thickness of skin, fleetness, visual acuity.

2. There must be differential survival and reproduction associated with the possession of that trait.
Graphically:



Heritable variation occurs by mutational changes in an organism’s DNA (any change in the hereditary message – base pair substitution or insertion/deletion of new bases) leading to the creation of new genetic material AND/OR creation of new genetic combinations through transposition (changing the position of a gene changes what it does), recombination (through cross-over during meosis), or genetic reshuffling (through sexual reproduction). Without getting too deep into it, selection can only act on the phenotype. A gene can be present, but not expressed (e.g. a recessive allele). Only homozygous recessives will show the trait and be selected for or against. In addition, selection acts on the whole organism (a conspicuously-colored moth, for ex, can have all sorts of wonderful genes, but if a bird nails that moth, its entire genotype is gone). And finally, selection doesn’t have to cause changes. It also can maintain the status quo.

Therefore, the general predictions of evolution are:

1. Given heritable variation over time, new species can and do arise.

2. 2. Over sufficiently long time periods, due to various mechanisms surviving populations will vary sufficiently from the parent population to constitute new taxa.

And that’s my description of evolution by random mutation and natural selection.

BTW: There are a couple of interesting corollaries to my definition. Basically, the above means that there is no requirement that evolution proceed in a linear fashion. Nor is it necessary that evolution produce either “greater complexity”, greater “perfection” or “greater information” (LOL) for evolution to be true. This is a creationist fallacy.
As an example, it is quite common to have an organism’s DNA contain multiple non-significant (unexpressed) or recessive alleles. Because these alleles serve no immediately useful function for an organism’s individual survival/reproductive success, natural selection simply ignores them. Meaning that if environmental conditions change there are generally individuals in a given population whose traits all of a sudden become important to their survival. This is one of the primary ways bacteria “develop” resistance to antibiotics: the resistance was already present in the population. All the antibiotics have done is eliminate all the members WHO DID NOT ALREADY HAVE THE TRAIT, increasing the overall frequency of alleles which are resistant within the population. The other way this happens, of course, is by bacterial gene swapping (bacterial sex!) which is almost Lamarckian in its implications.

Another marvelous outgrowth of evolution by natural selection is that often different combinations of genes or even macrostructures that are useful for one thing are found to be ultimately useful for something else, as well. These traits are then co-opted by natural selection to other uses.

Evolution as I’ve described it only requires a single step at a time AND each step needn’t (in fact shouldn’t) be considered in light of any subsequent step – only in comparison to its predecessor. New genes (hence new traits) do not arise because they are needed, and no organism ever made a living as a “transitional” – all were sufficiently well adapted for their particular niche and lifestyle to reproduce. Otherwise they would have quickly become extinct.

Hope this gets the discussion moving forward again.

unworthyone

Yeah I'm out of school about 5 years now so its rather difficult for me to grasp all this information. My stay is not long. So you can continue to try to explain but don't waste your time if you think the objective would be to change my mind. But first I'm going to need to grasp all this info.

[ April 06, 2002: Message edited by: unworthyone ]</p>

Automaton

The probabilities are incomparable because evolution is not chance (even though mutations are random).

unworthyone

No i'm not comparing them physically to be the same. I want to know the actual numerical probabilty of life springing from non-living matter. Why is this such a hard question?

Viti

unworthyone...as I have stated, I am no scientist.

What made me realize that abiogenesis (which is NOT addressed in evolution...please keep that in mind) was a real possibility was the existence of extremophiles...living organisms that do not depend on oxygen or sunlight. These interesting animals live in the thermal vents of the deepest ocean, inside active volcanoes, and in deep glacial ice. They live off of chemicals which are toxic to all other known forms of life. Fascinating little critters I suggest you read on.


edited because I am tired and stupid

[ April 06, 2002: Message edited by: LadyShea ]</p>

unworthyone

That would be like reading about unicorns. Its all make-believe supported by educated theory.

Viti

extremophiles are real living organisms...they exist today. Look them up, or watch Discovery Channels Blue Planet series...they took a special sub down several miles and got these things on film

I typed extremophobes earlier...I am going to bed....its extremophiles