Evolution Pros and Cons

[Galapagos]

If you really want to understand evolution, posting a bunch of quotes from the first creationist website that shows up on google on an internet forum is not an effective way to do this.

Originally Posted by questor

Quote:'' Tiktaalik is a transitional fossil; it is to tetrapods what Archaeopteryx is to birds. While neither may be ancestor to any living animal, they serve as proof that intermediates between very different types of vertebrates did once exist. '' This indicates that out of the thousands of fossils, two transitional were found? Is there any line of succession we can follow either backward or forward?

You should try a scientific source or wikipedia before looking to creationist websites questor.
THere are a great many transitional forms found, those are just two historically significant ones:
List of transitional fossils - Wikipedia, the free encyclopedia

Of course, most creationists at this point backpedal and then claim that they would need to see every single animal in a continuous gradation before they would accept this. Fortunately, with the help of DNA evidence, we can see how long ago lineages diverged and just how closely animals are related, and all of them share one common ancestor. Of course, all of this evidence is meaningless to creationists who already have their minds made up.

I also posted a summary of the transition in the lineage of elephants from a probing nose to the trunk over here, with several transitional fossils mentioned:
http://hypography.com/forums/biology...tml#post247324

Originally Posted by questor

The Project Steve proves nothing to me. You could have a million signatures on a subject and still be wrong.

That was the point. Science is not done by getting signatures. I now quote from the Project Steve page:

Creationists draw up these lists to try to convince the public that evolution is somehow being rejected by scientists, that it is a "theory in crisis." Not everyone realizes that this claim is unfounded. NCSE has been asked numerous times to compile a list of thousands of scientists affirming the validity of the theory of evolution. Although we easily could have done so, we have resisted. We did not wish to mislead the public into thinking that scientific issues are decided by who has the longer list of scientists!

You yourself just quoted one of these laughable lists. Had you actually read the project steve page, you would have seen that getting a bunch of signatures was not their point at all.

Originally Posted by questor

If evolution to you is variation in a species due to environmental factors, I say yes, they are readily observable. If evolution means all life descended from a primordial soup, I say give some hard evidence. Several of the quotes were from Darwin himself.

The quotes from Darwin were obviously out of context, and the pefectly adequate answer by Darwin ignored. The lack of transitional forms is only briefly mentioned in the chapter "Difficulties On Theory", and is dealt with more extensively in chapter 9 on "The Imperfection of the Geological Record". I now quote from the segment cherry-picked to show that he offers an explanation(bolded) that was also offered in this thread:
Literature.org - The Online Literature Library

Originally Posted by Darwin

On the absence or rarity of transitional varieties.—As natural selection acts solely by the preservation of profitable modifications, each new form will tend in a fully-stocked country to take the place of, and finally to exterminate, its own less improved parent or other less-favoured forms with which it comes into competition. Thus extinction and natural selection will, as we have seen, go hand in hand. Hence, if we look at each species as descended from some other unknown form, both the parent and all the transitional varieties will generally have been exterminated by the very process of formation and perfection of the new form.

But, as by this theory innumerable transitional forms must have existed, why do we not find them embedded in countless numbers in the crust of the earth? It will be much more convenient to discuss this question in the chapter on the Imperfection of the geological record; and I will here only state that I believe the answer mainly lies in the record being incomparably less perfect than is generally supposed; the imperfection of the record being chiefly due to organic beings not inhabiting profound depths of the sea, and to their remains being embedded and preserved to a future age only in masses of sediment sufficiently thick and extensive to withstand an enormous amount of future degradation; and such fossiliferous masses can be accumulated only where much sediment is deposited on the shallow bed of the sea, whilst it slowly subsides. These contingencies will concur only rarely, and after enormously long intervals. Whilst the bed of the sea is stationary or is rising, or when very little sediment is being deposited, there will be blanks in our geological history. The crust of the earth is a vast museum; but the natural collections have been made only at intervals of time immensely remote.
[...]
Lastly, looking not to any one time, but to all time, if my theory be true, numberless intermediate varieties, linking most closely all the species of the same group together, must assuredly have existed; but the very process of natural selection constantly tends, as has been so often remarked, to exterminate the parent forms and the intermediate links. Consequently evidence of their former existence could be found only amongst fossil remains, which are preserved, as we shall in a future chapter attempt to show, in an extremely imperfect and intermittent record.

Darwin gives the same explanation that is valid today. The odds that a body will fossilize are very low. If you doubt this, go kill a bunch of animals and try to have them preserved outside. You will find that only in certain rare naturally occurring scenarios will this happen. The fossil record looks exactly how evolutionary biologists and paleontologists would expect it to.

[questor]

Concerning the second law of thermodynamics, let's critique this quote:
"Evolutionary theory ignores this fundamental law of physics. The mechanism offered by evolution totally contradicts the second law. The theory of evolution says that disordered, dispersed, and lifeless atoms and molecules spontaneously came together over time, in a particular order, to form extremely complex molecules such as proteins, DNA, and RNA, whereupon millions of different living species with even more complex structures gradually emerged. According to the theory of evolution, this supposed process-which yields a more planned, more ordered, more complex and more organized structure at each stage-was formed all by itself under natural conditions. The law of entropy makes it clear that this so-called natural process utterly contradicts the laws of physics.

Evolutionist scientists are also aware of this fact. J. H. Rush states:

In the complex course of its evolution, life exhibits a remarkable contrast to the tendency expressed in the Second Law of Thermodynamics. Where the Second Law expresses an irreversible progression toward increased entropy and disorder, life evolves continually higher levels of order.365

The evolutionist author Roger Lewin expresses the thermodynamic impasse of evolution in an article in Science:

One problem biologists have faced is the apparent contradiction by evolution of the second law of thermodynamics. Systems should decay through time, giving less, not more, order.366

Another defender of the theory of evolution, George Stravropoulos, states the thermodynamic impossibility of the spontaneous formation of life and the impossibility of explaining the existence of complex living mechanisms by natural laws in the well-known evolutionist journal American Scientist:

Yet, under ordinary conditions, no complex organic molecule can ever form spontaneously, but will rather disintegrate, in agreement with the second law. Indeed, the more complex it is, the more unstable it will be, and the more assured, sooner or later, its disintegration. Photosynthesis and all life processes, and even life itself, cannot yet be understood in terms of thermodynamics or any other exact science, despite the use of confused or deliberately confusing language.367

As we have seen, the evolution claim is completely at odds with the laws of physics. The second law of thermodynamics constitutes an insurmountable obstacle for the scenario of evolution, in terms of both science and logic. Unable to offer any scientific and consistent explanation to overcome this obstacle, evolutionists can only do so in their imagination. ''

[Galapagos]

Originally Posted by HydrogenBond

Here is a good evolutionary test. The theory is random mutations leads to adaptions to the environment via selective advantage. To test this, we will start with mice and artificially induce random mutations. We can't use logic to plan the mutations, since that would prove genetics evolves using some rational schema.

What should happen, if the theory is correct, is not only the perpetuation of the mice sample, but better adaptation. If we mess up successive generations of mice, due to random mutations, it would show random will not work and the theory is wrong at least in part.

No. Most random mutations either occurring naturally or induced will be deleterious, and if the population goes extinct when you blast it with radiation, this does not show that natural selection does not work. Natural selection not only requires variation, it also requires differential reproduction and heritability.

I don't think you understand how evolution by natural selection works:

1. Random variation (mutation, recombination etc)

2. Heredity(some variation must be passed on, cumulatively, to offspring)

3. Differential reproduction(some inherited variation must increase the fitness of its bearers)


If a random mutation which produces a trait occurs that increases fitness in the environment, the trait will increase in population as those with it reproduce/survive better than those without.
Mutation by itself is not enough.

[Galapagos]

Originally Posted by questor

Moon, let me put it another way. How do you explain such diversity in fossil strata? If the animals in the layer were all exposed to a similar environment, why wouldn't they develop similar traits? Why would some eat meat and others grass? Why would some grow wings and others grow horns? Do their genes have some kind of signal mechanism that says.. I need wings, let's grow some?

There are many ways to make a living on Earth. Organisms evolve to get the energy they need in any open ecological niche. If some aquatic organism is better at getting food near the surface and another faces extinction, perhaps the challenged organism will flatten out, and feed and find cover on the bottom. This is what evolved twice in the lineage of rays/ skates and unrelated flatfishes. This is an example of convergent evolution.
The rays flattened on the belly, but the flatfishes(like soles, halibut, and plaice) flatted by laying on one side. This has resulted in a very wasteful and imperfect design in flatfishes, where during development their face slowly moves to one side, with both eyes facing up. IT is worth mentioning that hese imperfections(such as the way our eyes are wired backwards) are quite difficult to square with the belief in magical creation by a perfect designer, but quite in line with the idea of gradual evolution adapting organisms to immediate environments.

Originally Posted by questor

By the way, can you give an example of a succesful mutation that can be heritable?

Darwin's finches - Wikipedia, the free encyclopedia

The case of the Galapagos Finches has been documented extensively. Peter and Rosemary Grant followed them through several draughts and watched the environment change the frequencies of beak shape in the population. There is also a segment on the wiki page about the molecular basis of the change.
This is one of a great many examples that could be brought up.

[freeztar]

Originally Posted by questor

Moon, let me put it another way. How do you explain such diversity in fossil strata? If the animals in the layer were all exposed to a similar environment, why wouldn't they develop similar traits? Why would some eat meat and others grass? Why would some grow wings and others grow horns? Do their genes have some kind of signal mechanism that says.. I need wings, let's grow some?

Those are good questions questor.
The short answer is that different organisms occupy different ecological niches combined with the evolutionary processes of natural selection, genetic drift, and population isolation->speciation.

Imagine this scenario from, say, 100 mya in Australia. A species of frog adapted to living in the rainforest undergoes a population explosion (perhaps because of many good years of rain or food, or an extinction of one of their top predators). Resources are always a limiting factor, so the frogs compete heavily for food, mating grounds, etc. Some frogs venture to the outskirts of the rainforest to take advantage of untapped resources (new food sources, etc.). Some of these frogs die because they cannot deal with the new environmental factors (new food sources, change in micro-climate, inadequate breeding grounds, etc.). But, some of these frogs survive due to a different genetic makeup/fitness that allows them to tolerate these new environmental conditions. These frogs reproduce and through time begin to adapt better to their new home. Fast forward 50 million years and analyze a frog from the center of the rainforest, and those on the edge. You might find that the frogs in the interior have retained much of their morphology and even genetics, whereas those frogs on the outskirts have changed their morphology/genetics to better adapt to their new environment. (they might have less webbing on their feet due to drier conditions, or maybe they adapted poisons to deal with the new predators, etc.)

This is a very simple thought experiment that is meant to illustrate how speciation occurs. When you figure in the complex web of life, it is easy to see how complicated it can get.

Also, it's important to realize that 50 million years is a *long* time. Scientists today can invoke adaptations in microorganisms in far less time than an average human lifetime. When you multiply this out to something like 50 million years, the possibilities become staggering.

By the way, can you give an example of a succesful mutation that can be heritable?

I believe you are referring to germ line mutations.
As MTM noted earlier in this thread, the vast majority of hereditary mutations are not beneficial. For a list of some beneficial mutations, check out the following link.

Examples of Beneficial Mutations and Natural Selection

[Galapagos]

Originally Posted by freeztar

I believe you are referring to germ line mutations.
As MTM noted earlier in this thread, the vast majority of hereditary mutations are not beneficial. For a list of some beneficial mutations, check out the following link.

Examples of Beneficial Mutations and Natural Selection

You mention above that scientists can observe evolution occurring in microbes due to their short generations. This reminded me of the excellent example put forth by Lenski et al earlier this year, as published in the PNAS, and covered extensively in various media outlets:
Historical contingency and the evolution of a key innovation in an experimental population of Escherichia coli ? PNAS

The role of historical contingency in evolution has been much debated, but rarely tested. Twelve initially identical populations of Escherichia coli were founded in 1988 to investigate this issue. They have since evolved in a glucose-limited medium that also contains citrate, which E. coli cannot use as a carbon source under oxic conditions. No population evolved the capacity to exploit citrate for >30,000 generations, although each population tested billions of mutations. A citrate-using (Cit+) variant finally evolved in one population by 31,500 generations, causing an increase in population size and diversity. The long-delayed and unique evolution of this function might indicate the involvement of some extremely rare mutation. Alternately, it may involve an ordinary mutation, but one whose physical occurrence or phenotypic expression is contingent on prior mutations in that population. We tested these hypotheses in experiments that “replayed” evolution from different points in that population's history. We observed no Cit+ mutants among 8.4 × 1012 ancestral cells, nor among 9 × 1012 cells from 60 clones sampled in the first 15,000 generations. However, we observed a significantly greater tendency for later clones to evolve Cit+, indicating that some potentiating mutation arose by 20,000 generations. This potentiating change increased the mutation rate to Cit+ but did not cause generalized hypermutability. Thus, the evolution of this phenotype was contingent on the particular history of that population. More generally, we suggest that historical contingency is especially important when it facilitates the evolution of key innovations that are not easily evolved by gradual, cumulative selection.

The Loom : A New Step In Evolution
http://www.nytimes.com/2007/06/26/sc...f9d4c6&ei=5070

[Zythryn]

Originally Posted by questor

The evolutionist author Roger Lewin expresses the thermodynamic impasse of evolution in an article in Science:

One problem biologists have faced is the apparent contradiction by evolution of the second law of thermodynamics. Systems should decay through time, giving less, not more, order.366

Questor, this is a partial quotation. For the full context perhaps you should read, or include if you already read it, the second part:

One legitimate response to this challenge is that life on earth is an open system with respect to energy and therefore the process of evolution sidesteps the law's demand for increasing disorder with time.

This is from Science, September 1982 Volume 217.
Now, this is the only one I checked, will we find similar errors if we can actually find the sources of the quotes for the others?

Your source of information is in error and is either intentionally trying to mislead you, or was mislead themselves.

[ughaibu]

Originally Posted by questor

This indicates that out of the thousands of fossils, two transitional were found?

You're joking, I hope.

Originally Posted by questor

Is there any line of succession we can follow either backward or forward?

The cliche is horses. Really, surely everybody came across this before they were ten years old.

[questor]

The change of the beaks of the finches only shows that changes can occur in species, NOT create a new species.

Ugh, if you are referring to an eohippus evolving to a modern horse the same as above applies to it.

The crux here is the claim that all species evolved from a single cell life form.

[ughaibu]

Originally Posted by questor

The crux here is the claim that all species evolved from a single cell life form.

This is what you want transitional fossils for?