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Author
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Topic: Is evolution intelligent?
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Matt F.
Member
Member # 1215
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posted 23. March 2004 18:33
Sorry for my amateurish understanding of biology and evolution. I am a journalist but need to do some research on the topic. Any feedback is much appreciated; links to relevant sites are definitely welcome too.
My understanding of darwinian evolution:It is driven by 2 factors. Mutation and selection. Mutation is random; those mutations that are accidentally favourable in a changed environment will survive and prosper, the others will die out.
My conclusions: Emergence of new species must be gradual, and in relation to the amount of existing lifeforms. And we should find all kind of lifeforms that have failed, like giraffes with thick instead of long necks.
Questions:
- Don't we observe just the opposite? Emergence of completely built species at the cambrian age, and sudden emergence of new species of mammals after the dinosaurs had gone? Would that speak against random mutation? Is it feasible that not only the individual, but evolution "learns" what's going on in the environment and adapts? Maybe through stress-signals that are processed in the DNA. I know that Lamarckism has been refuted, but it would make a lot of sense!!
- Why don't we find more "evolutionary trash" ie: those species that would emerge in a random mutation but would be short-lived? Could time have wiped out all traces? Or is that another indication against random mutation?
Thanks for any ideas!
Matt
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Rex Kerr
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Member # 632
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posted 24. March 2004 01:13
One must understand that fossilization selects for "winners", and looks at individual spots through time. This is merely common sense, on reflection: fossilization is rare, so the most common species will be the easiest to find, and you only get exposed fossils in a fairly limited location.
This explains both of your points, in part. The weird failed life-forms are outnumbered by the successful ones by millions to one (or trillions to one), so we shouldn't expect to see them.
And when you get a gradual change in the range of two competing, closely related species (e.g. over 100,000 years), in the fossil record it looks like an abrupt jump from one species to the other.
These features of fossilization are both extremely irritating, and it is the reason why paleontologists are so excited to find "missing links". They're not expected to be terribly common. It also make it more difficult to validate the evolutionary hypothesis, since although there are many intermediate forms that have been found, there are also many missing (and we should not be surprised).
The Cambrian explosion is a slightly different event--there are a supremely large number of species that appear in a surprisingly short period of time. It's a bit of a puzzle, but fossil records from that time are few and far between, so it's hard to tell if it's a disaster, or if there's something that we've overlooked that explains the sudden diversification.
For a great deal of information on evolution from a layperson's perspective, I suggest starting with the talk.origins archive. Their FAQ contains answers both your questions, and many others besides.
[ 24. March 2004, 01:14: Message edited by: Rex Kerr ]
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Jurie
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Member # 716
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posted 24. March 2004 06:32
quote:
The weird failed life-forms are outnumbered by the successful ones by millions to one (or trillions to one), so we shouldn't expect to see them.
Could you elaborate? I thought Darwinism meant species changed/improved gradually through time, so the specific prediction is that we should see a bewildering mix of fossils with not much stasis. What you say sounds very much like special pleading, since we see the opposite. Do you mean punk-eek?
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John Wendt
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Member # 798
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posted 24. March 2004 08:30
Matt,
Normally I wouldn't reply to a request like yours; too many people come here with religious agendas, and resist any attempt at reason. As a journalist, though, you can be dangerous, so I'll make an attempt.
The "random mutation plus natural selection" stereotype is so far out of date as to be almost a strawman. This page is a good start on the modern view: The form of an organism is determined, at least in part, by its genes. Biologists have believed for a long time that genes fall into two classes: structural and control. Structural genes produce the proteins that make up tissues; control genes control the actions of structural genes.
Molecular biology has given biologists the tools to investigate exactly how this happens. A textbook on developmental biology would help you, although it might be tough going. This site is a resource for teachers.
As to "evolutionary trash": There's a lot of it in the human genome, in the form of pseudogenes. This page is one example.
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Pim van Meurs
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Member # 541
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posted 24. March 2004 11:57
Jurie: Could you elaborate? I thought Darwinism meant species changed/improved gradually through time, so the specific prediction is that we should see a bewildering mix of fossils with not much stasis. What you say sounds very much like special pleading, since we see the opposite. Do you mean punk-eek?
This is a common confusion as to what Darwinian's theory is all about. Darwin's theory is variation AND selection. IF a new mutation/variation arises which is detrimental then it will quickly be eliminated from the population, if however new mutations arise which are benificial these mutations will spread quickly. So how do you reach the conclusion that Darwinian theory predicts a bewildering mix of fossils?
The fossil record btw shows both excellent examples of 'stasis' as well as 'gradual evolution' in nice support of Darwinian theory, it even provides us with (the expected amount of) transitional fossils. When simulating Darwinian evolution in RNA for instance not surprisingly we find the same periods of stasis followed by quick innovation.
So I would argue that your expectations may not be in line with what Darwinian theory would expect but I am interested to hear your side of the argument.
Reptile to mammal transitionals
Smooth transitions see link for more info
The Cambrian period is quite interesting since we find most of the fossils for phyla in this period although there are a growing number of pre-Cambrian fossils and phylogenetic data that suggest that various phyla arose much earlier.
Some recent ideas on the Cambrian explosion include a preceding extinction event, the increase of O2 or this nature link claims that
Plants detonated Cambrian explosion Global cooling may have allowed complex animals to flourish.
An exquisite fossil find in China, the Chengjiang Fossil Fauna in Yunnan Province, shows more evidence of what may have happened
In this Chinese newspaper article they describe this event as
quote:
Chinese scientists first discovered the general outline of the explosion through studies on the Chengjiang Fossil Fauna in Yunnan Province, and proved that ancestors of almost all animals were once on the same starting line. The achievement is "an important development to Darwin's evolution theory".
See also this recent paper
The colonization of land by animals: molecular phylogeny and divergence times among arthropods
BMC Biology 2004, 2:1, Pisani et al
quote:
Results: Significant support was found for the unconventional pairing of myriapods (millipedes and centipedes) with chelicerates (spiders, scorpions, horseshoe crabs, etc.) using nuclear and mitochondrial genes. Our estimated time for the divergence of millipedes (Diplopoda) and centipedes (Chilopoda) was 442 ± 50 Ma, and the divergence of insects and crustaceans was estimated as 666 ± 58 Ma. Our results also agree with previous studies suggesting a deep divergence (~1100 – 900 Ma) for arthropods and deuterostomes, considerably predating the Cambrian Explosion seen in the animal fossil record.
[ 24. March 2004, 12:11: Message edited by: Pim van Meurs ]
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Rex Kerr
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Member # 632
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posted 24. March 2004 14:12
Jurie wrote:
quote:
I thought Darwinism meant species changed/improved gradually through time, so the specific prediction is that we should see a bewildering mix of fossils with not much stasis.
Gradual is a relative term. It takes much longer for slightly beneficial mutations (especially pairwise beneficial mutations) to spread through a species with a very large effective population size than one with a small effective population size. However, you expect to find fossils from species with large actual populations, so you would expect more rapid changes in small subpopulations than in the main population even though you're probably watching the main one. So on human timescales change is gradual, but you may not always see it in the fossil record because of the relative difficulty of changing a huge population through interbreeding--speciation in a small population, followed by replacement of the original, is simply easier mathematically.
How many different forms you have depends very much on the topology of fitness space. Specifically, if almost all forms are equally good, or potential for improvement is slow but unlimited, you'd expect to see your bewildering mix of forms. If, in contrast, there are a fairly narrow range of forms that are really "fit" for a given niche, then you'd expect to see a small set of forms dominated by those who first found a "fit" form for a particular niche (who then compete out everyone else, thus denying them a chance to adapt to that niche).
Reality is somewhere in between those two extremes. However, my impression is that most species don't have all that many competitors within their niche, which indicates that the situation is more towards the latter extreme than the former.
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Jurie
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posted 24. March 2004 17:30
Thanks, Pim. I will work through the pointers you gave. But something you said sounds dissonant:
quote:
it even provides us with (the expected amount of) transitional fossils
Doesn't history show that everybody from Darwin to Gould expected there to be a LOT more transitional fossils? And when hardly more were found, Darwinism had to be modified to explain this lack? But now it appears that the situation is reversed: You say Darwinism predicts the expected amount of transitional fossils. But the evidence was substantially in conflict with gradualism, this had to be explained away, and now that problem is claimed to be the expected result. This sounds really bad, like a theory is formulated to explain observed phenomena, then afterwards claiming the theory predicted those phenomena in the first place.
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Rex Kerr
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posted 24. March 2004 22:12
I don't think it provided us with the expected number of transitional fossils. I think people expected more. I also think people were naive and did not carefully think through the relationship between evolutionary pressures, ecology and population ranges, and what you see in the fossil record.
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Moderator
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Member # 1
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posted 25. March 2004 12:09
This thread is too ambiguous. Matt F, I appreciate your need for information, but this isn't the place to generically ask for it. Try www.arn.org or other websites. This is a technical forum for discussing novel ideas, insights, and intuititions.
If no direction is given to this thread today, it will be closed down. Incidentally, the title of this thread suggests an interesting direction: is evolution intelligent?
Moderator
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Pim van Meurs
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Member # 541
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posted 27. March 2004 20:59
quote:
Pim: it even provides us with (the expected amount of) transitional fossils
Jurie: Doesn't history show that everybody from Darwin to Gould expected there to be a LOT more transitional fossils?
Yes
Jurie: And when hardly more were found, Darwinism had to be modified to explain this lack?
Nope. What needed to be modified is the expectations. Although Gould did propose punkeek as an explanation.
Jurie: But now it appears that the situation is reversed: You say Darwinism predicts the expected amount of transitional fossils.
Nope, I am saying that the fossil record shows evidence of transitional in numbers very similar from what may be expected from such parameters as fossilization etc.
Or in other words, taking estimates of various parameters, one can estimate the expected number of transitionals and compare this to the actual number.
I quote Welsey Elsberry's post of the month february 1998:
quote:
Given these views of Darwin, we can derive an expectation of the ratio of transitional to non-transitional fossils found. I include in the following only those factors which yield a differential expectation of discovery of transitional fossils displaying the action of natural selection.
EFR = (NSTP * NSPP * AP * SEVR * FSDP)
and
ETF = EFR * OFS
where EFR is the "expected fossil ratio",
NSTP is the "natural selection time proportion",
NSPP is the "natural selection population proportion",
AP is the "area proportion",
SEVR is the "subsidence vs. elevation variation ratio",
FSDP is the "formation to species duration proportion",
ETF is the "expected number of transitional fossils",
and OFS is the number of "observed fossil species".
Now, we can assign some estimated numbers to the variables listed above. Because Darwin said "often only at long intervals", NSTP should be small. Let's assign a relatively large "small" value of 0.1. Since Darwin said that natural selection operates on only a very few inhabitants at a time, NSPP should be smaller still than NSTP. Let's assign a value of 0.01. For AP, the area proportion between the geographic extent of a widely ranging species and its local variety, a value of 0.1 is probably an overestimate, but let's leave it at that for the moment. For SEVR, Darwin's text would indicate a value of 0.25 or less would be reasonable. FSDP is something best estimated by a geologist, but Darwin probably felt it to be under 0.5. Replacing values, we find that
EFR = 0.1 * 0.01 * 0.1 * 0.25 * 0.5
EFR = 0.0000125 = 1/80,000
David Raup has estimated the number of catalogued fossil species at 250,000. This allows us to generate an estimate for number of transitional sequences expected under Darwin's own views as:
ETF = EFR * OFS = 0.0000125 * 250,000 = 3.125
Roger Cuffey's 1974 paper on paleontologic evidence listed references for at least 139 fine-grained species to species transitional sequences. According to an expectation derived from Darwin's own words and values from the real world, it can be seen that the fossils have been rather more forthcoming than one would expect, not less.
[ 28. March 2004, 15:02: Message edited by: Pim van Meurs ]
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