RufusAtticus

Actually, mutation and natural selection are the most powerful answer science has to offer. If you don't understand the mechanisms and strengths of evolution, you should go back to school. If you don't want to do that you should pay attention to the articles at <a href="http://www.talkorigins.org" target="_blank">http://www.talkorigins.org</a>.

Nice assertion sans argument. No scientists claims that evolution ever does produce "new" structures or organs. Evolution only modifies what its got. Sometimes that modification will result in novel features and attributes, such as wings evolving from arms.

Actually, there is much evidence for common descent found in the fossil record and comparative genomics. Would you care to offer an alternate explaination that better explains the oberserved evidence that evolution and common descent?

Do you believe that creatures have existed as immutable kinds with limited evolutionary possibility since the dawn of time? What do you have to support this claim? Can you identify the genetic barrier that establishes this limitation of evolution? What would prevent a population of dogs from evolving so much that they lose diagnostic features and/or gain novel ones? Unless you can show that there is no way for this to happen, you cannot safely say that dogs and cats do not share a common ancestor.

Furthermore, how much genetic change does it take to turn a single cell into a walking, breathing, and voting American?

-RvFvS
P.S. I would be happy to have a formal debate with you with respect to the existance of immutable kinds.

Quetzal

Thanatos: There's a bit you don't seem to understand about how critters navigate. (Since I'm too lazy to look up anything new, here's a re-hash of an old post):

Birds use a multiplicity of navigational tools to get from point A to point B. These tools include:
The dominance of one tool over another in a particular migratory species depends on environment and the particular problems the species faces. Which of course, is entirely consistent with evolutionary theories and natural selection.

For example, the bobolink (Dolichonyx oryzivorus), a North American songbird, migrates 7000 miles annually from Alaska to Argentina. It uses two different magnetic sensors (magnetite and chemical photoreceptors in its eyes), and celestial navigation (to occasionally re-calibrate its magnetic compass). It does not, however, need to worry about magnetic declination (i.e. east-west variation). Experiments such as the one <a href="http://www.nwf.org/nationalwildlife/1999/compass.html" target="_blank">on this site</a> show that bobolinks deprived of their magnetic sensing ability and provided ONLY with stars for navigation, get completely turned around. On the other hand, ornithologists Kenneth and Mary Able, both of the State University of New York at Albany, have found that Savannah sparrows (Passerculus sandwichensis beldingi), who migrate substantially less distance, rely more on celestial cues to make adjustments to their magnetic compass and compensate for the changes in declination, since their migration, although shorter, has a significant east-west component. See <a href="http://www.nwf.org/nationalwildlife/1999/compass.html" target="_blank">“Navigating with a Built in Compass”</a> for more details.

In addition, for those who would like more information on magnetic sensing in animals, not just birds, see <a href="http://www.ks.uiuc.edu/~ritz/RESEARCH/MS/ms.html" target="_blank">this article</a> or <a href="http://serendip.brynmawr.edu/bb/neuro/neuro00/web1/MathraniVand.html" target="_blank">this one</a>.

[Edited to fix UBB code]

[ April 17, 2002: Message edited by: Morpho ]</p>

Oolon Colluphid

&lt;sigh&gt; SSDC... same shit, different creationist...

Experimentally? Experiments are great when available, but for many areas, such as astronomy, palaeontology and geology, they aren’t. But experiments are just one way of testing predictions that a hypothesis makes, potentially falsifying them. Evolution, for instance, makes predictions about what should be found in the fossil record. An example: studies of pig embryonic development (eg Reichert 1937) showed that ear bones start out as part of the jaw cartilage, and move to the inner ear. From this, it was predicted that mammalian inner ear bones were originally jaw bones in the reptilian ancestors, that took on another use. (Aside: modern snakes hear with their jaws.) This prediction might be confirmed from the fossil record. It has been. There is an elegant series of transitions from reptile to mammal, the cynodont therapsids -- see <a href="http://www.gcssepm.org/special/cuffey_05.htm" target="_blank">here</a> and <a href="http://www.talkorigins.org/faqs/comdesc/section1.html#pred4ex2" target="_blank">here</a> -- that show the jaw bones moving to a new function in the inner ear.

That much is fact; whether these changes were due to mutation and natural selection might be debateable. However, we do know that mutation and selection can produce novelty. An example: certain bacteria have mutated to digest nylon oligomers -- short molecules found in the waste waters of nylon plants, which have bonds that do not occur in nature. This has also been reproduced experimentally. When non-nylon-metabolising strains of Pseudomonas were grown with nylon oligomers as the primary food source, within a relatively small number of generations they developed these enzyme activities. (Negoro et al, 1994, ‘The nylon oligomer biodegradation system of Flavobacterium and Pseudomonas’, Biodegradation 5: 185-194.)

Limited by what? Please explain how you know they’re limited.

&lt;sigh&gt; Nothing is ever proven in science...

How about what can happen in a mere few hundred or thousand?







Do please tell us what is to stop such changes producing new kinds?

Please define ‘kind’. Is it equivalent to species, genus, family, order... or something else? How do you tell kinds apart? Are humans and chimpanzees different kinds?

TTFN, Oolon

Vorkosigan

Thanatos -- you didn't list an email, but I am in Taichung. Drop me a line, or take a look at my website:

<a href="http://users2.ev1.net/~turton/teach_index.html" target="_blank">http://users2.ev1.net/~turton/teach_index.html</a>

Michael

Thanatos

Oolon Colluphid

Huh?

Nothing to say, I guess.

Oolon

Thanatos

Correct me if I'm wrong, but does macroevolution (simply put) not claim that basic life-forms evolved into more complex life-forms? ie. fish, amphibians, reptiles, birds, and mammals. I fail to see how natural selection and mutations explain how this happened.

Don't organisms stay true to type? Is change not limited? Dog breeding has resulted in many varieties from a Greyhound to a Terrier, but none has left the canine family. They represent cyclical change in gene frequencies but no new genetic information. They haven't evolved to a new level of complexity. They have merely variated around a mean. Can you give me an observable example that is not 'variation within kind'?

Aren't most mutations harmful and often lethal to an organism?

Can you give me an example where mutations have resulted in the creation of new structures - or more complex structures?

I haven't been able to find a scientific journal that contradicts the basic principle that change in living things is limited. In fact, I have found the opposite. Luther Burbank came up with the law of the Reversion to the average. He said organisms stay true to type and that all living things are bound by fixed limitations. (Norman Macbeth, Darwin Retried New York: Delta, 1971)

Godless Dave

That's incorrect. Organisms evolve into forms that are better able to survive in their environment. They aren't necessarily more "complex". If increased complexity provides a survival advantage, it will be selected. But it's not always an advantage.

No. No.

That's because it's breeding, not evolution. Breeders breed for existing traits, they don't select dogs with mutations and try to direct them towards a new species.

However, dogs (canis familiaris) did evolve from wolves (canis lupus). That's one species evolved from another.

No, most mutations are benign; they don't do anything. Some are harmful. A few are beneficial.

For instance, like most humans of Northern European descent, I have a mutation that allows me to digest dairy products. Not all humans can do that.

The lungfish. Various varieties of lungfish live in Africa and Australia. They have both lungs and gills, both of which allow it to take in oxygen (the lungs from the air, the gills from water). They evolved from regular fish, who only took in oxygen through their gills. They had an air bladder that was used for controlling ascent and descent in the water. The ancestor of the lungfish had a mutation (or series of mutations) that turned the air bladder into a lung that could breathe in air and pass oxygen to the bloodstream.

There are some in the Chicago aquarium. They're really cool.

Since Darwin Retried is a book, not a scientific journal, and is 20 years old to boot, I suggest you look harder. Try the journal Nature.

Mageth

Thanatos:

Here is a link to a page containing an image comparing the cmromosomes of the four known, presently living members of the family Hominidae:

<a href="http://www.geocities.com/focus68/hominoid.html" target="_blank">link, in more ways than one</a>

(note: the page apparently is speculation about Bigfoot, but ignore that part; the genetics info is what I'm interested in)

Looking at this, it's impossible for me to believe (and I think it's ignorant for anyone else to believe) that we do not share common ancestor(s) with the Great Apes. And I would say the human brain is a "more complex structure" than the brains of any of the other three members of our Family.

[ April 17, 2002: Message edited by: Mageth ]</p>

Oolon Colluphid

Nope. Life-forms do not evolve, lineages do. Macroevolution, insofar as the word means anything except to creationists, is simply evolution above the species level.

Then open your eyes in front of this online biology textbook:
<a href="http://gened.emc.maricopa.edu/Bio/BIO181/BIOBK/BioBookTOC.html" target="_blank">http://gened.emc.maricopa.edu/Bio/BIO181/BIOBK/BioBookTOC.html</a>

Mutations are random copying errors in DNA. Mutations can be neutral (neither helpful nor harmful), strictly harmful, strictly beneficial, or (and this is important) more commonly, whether they are harmful or helpful depends on the environment -- including the other genes it finds itself with. In practice most mutations are neutral, and are the cause of ‘genetic drift’. Moreover, a mutation may be favourable in the sense that it permits survival in an unfavourable environment, and yet be unfavourable in a better or more usual environment. For instance, there is a genetic disorder, phenylketonuria, caused by a mutation in the gene that produces phenylalanine hydroxylase, which breaks down excesses (beyond bodily needs) of this amino acid. As homozygous individuals develop through infancy, the excess phenylalanine leads to mental retardation. If such an individual is brought up in an environment free of phenylalanine, however, the trait does not show itself. Thus if the general diet were different, it would not be disadvantageous.

Natural selection is a filtering algorithm. It acts on the genes like a sieve: only those things best able to survive (or even none) from each generation get to play in the next round. The algorithm bit is that this process is repeated at each generation. (Steve Jones has called life an exam with two papers: getting born and growing up, and leaving offspring.) Stack up thousands and millions of sieves, and what you get out the end is stuff that’s good at getting through sieves -- organisms that are good at surviving and reproducing. Since there are a wide range of ways to make a living, the genes that pass down generations, through the sieve of selection, can diverge into bodies good at living in different niches.

Natural selection ratchets the designs forward -- not necessarily to complexity: viruses, for example, are models of highly evolved simplicity -- by only keeping the good stuff, and any improvements that turn up.

Define, as I have already requested, type. A Great Dane can no longer breed or have viable offspring with a Chihuahua; mallards and pintails do not naturally hybridise, and are considered separate species, though occasionally they do interbreed in zoos. What is a kind?

Generation-to-generation change is, because a random large change is most likely to produce a random large cock-up. That’s why evolution works incrementally. There is nothing we know of that means cumulative small changes cannot radically alter an organism. If such populations diverge, they may ultimately be too different to interbreed, or to even be recognisable as being from the same ancestor. See for instance these <a href="http://www.botany.hawaii.edu/faculty/carr/radiation.htm" target="_blank">Hawaiian silverswords</a>. Are they one kind, or several? If such long-term change is limited somehow, please explain how, and how you know.

Aha! So ‘kind’ = family. Do you actually mean the Canidae?

What do you mean by ‘genetic information’?

In a few thousand years at most? Maybe not. What do you make of, say, the gradual differentiation of teeth in the cynodonts I linked? Is having more than one kind of tooth more complex than having them all the same?

Since dogs are a subspecies of wolf (Canis lupus familiaris), it looks to me as if things like St Bernards and Pekineses have diverged from whatever the ‘mean’ is for a wolf. How do you know they are still the same ‘kind’ (whatever that means)? If you think they are because they can (mostly) still interbreed, then you cannot think kind = family, for the arctic fox (Alopex lagopus), small-eared dog (Atelocynus microtis), maned wolf (Chrysocyon brachyurus), African hunting dog (Lycaon pictus), racoon dog (Nyctereutes procyonoides), grey fox (Urocyon cinereoargenteus), and a whole bunch of others, show the diversity in the Canidae, and they cannot interbreed. You’ll note that they’re not even classified in the same genus.

Not till you define kind.

Nope. Covered above.

Yup. Mutation of the Hox genes were responsible for the divergence of insects and crustaceans. See
<a href="http://www.nature.com/nature/links/020221/020221-1.html" target="_blank">www.nature.com/nature/links/020221/020221-1.html</a>
<a href="http://www.cosmiverse.com/science02250202.html" target="_blank">www.cosmiverse.com/science02250202.html</a>
And then try the original paper:
<a href="http://www.brembs.net/metabiology/mcginnis.pdf" target="_blank">www.brembs.net/metabiology/mcginnis.pdf</a>

(Now where’s the damned threads on that? )

Try also here: <a href="http://www.nyu.edu/projects/fitch/courses/evolution/html/origins_of_novelty.html" target="_blank">Origins of novelty</a> for more general stuff.

Have you tried Nature, Science, PNAS, Evolution, Proceedings B of the Royal Society, Journal of Molecular Evolution, Journal of Vertebrate Paleontology, Molecular Phylogenetics and Evolution, annual Review of Ecology and Systematics, Journal of Human Evolution, Systematic Biology, Journal of Zoology, Developmental Biology, Brain, Behavior and Evolution, The American Zoologist, Plant, Cell & Environment, Herpetological Review, American Journal of Botany, Heredity....?

Creationist book = scientific journal. Hmm. No wonder you’re confused.

TTFN, Oolon