Freethought & Rationalism Archive

AbbyNormal · 12-18-2002, 08:56 AM

I thought I'd throw this out to the brilliant members of this board. What are current thoughts on the notion that the earth isn't old enough for such biological diversity to have arisen from solely naturalistic processes? What *is* the timescale required for evolution? I'm having great difficulty finding information...I'm sure it's buried in talkorigins somewhere, I'm just having little luck finding it. Or maybe I'm just inept at searching.

Thanks so much for any help!

Regards,
AbbyNormal

tgamble · 12-18-2002, 10:10 AM

Quote:

Originally posted by AbbyNormal:
<strong>I thought I'd throw this out to the brilliant members of this board. What are current thoughts on the notion that the earth isn't old enough for such biological diversity to have arisen from solely naturalistic processes?

Such thoughts come only from fundies who a) think the earth is only a few thousand years or b) those who accept the old age but use probability arguments that evolution couldn't happen in a hundred gazillion billion trillion guggillian years.

Quote:

What *is* the timescale required for evolution?

whatever the age of the earth is I guess. 4.5 billion years.

Quote:

I'm having great difficulty finding information...I'm sure it's buried in talkorigins somewhere, I'm just having little luck finding it. Or maybe I'm just inept at searching.

Thanks so much for any help!
Regards,
AbbyNormal</strong>

Age of the earth issues are discussed but beyond that, it's not really clear what you mean by the "timetable required for evoluiton"

Zadok001 · 12-18-2002, 12:23 PM

tgamble:

If I'm interpretting correctly, this is a key issue. I've actually wondered about it myself. We have an ENORMOUS variety of life here on Earth. The question is, how many millions of years would be required for a single common ancestor to evolve into the variety we see today. (Obviously, the circular solution is to say "However long it's been since abiogenesis." But that's no good. We're looking for evidence for or against evolution, citing evolution is not a good way to do that.)

Is that clearer?

Tim Thompson · 12-18-2002, 12:29 PM

AbbyNormal: What *is* the timescale required for evolution?

Here are two examples that seem to provide template answers for the question. They are not based on any a-priori bias regarding the age of the Earth. Rather, the timescales are derived directly from observed rats of molecular evolution. Since those timescales are well within the scope of the independently derived age of the Earth, and independently derived geologic time scales, they would seem to be consistent with our knowledge of nature.

A molecular timescale for vertebrate evolution
S. Kumar & S.B. Hedges
Nature 392(6679): 917-920, April 30, 1998
Abstract: A timescale is necessary for estimating rates of molecular and morphological change in organisms and for interpreting patterns of macroevolution and biogeography. Traditionally, these times have been obtained from the fossil record, where the earliest representatives of two lineages establish a minimum time of divergence of these lineages. The clock-like accumulation of sequence differences in some genes provides an alternative method by which the mean divergence time can be estimated. Estimates from single genes may have large statistical errors, but multiple genes can be studied to obtain a more reliable estimate of divergence time. However, until recently, the number of genes available for estimation of divergence time has been limited. Here we present divergence-time estimates for mammalian orders and major lineages of vertebrates, from an analysis of 658 nuclear genes. The molecular times agree with most early (Palaeozoic) and late (Cenozoic) fossil-based times, but indicate major gaps in the Mesozoic fossil record. At least five lineages of placental mammals arose more than 100 million years ago, and most of the modern orders seem to have diversified before the Cretaceous/Tertiary extinction of the dinosaurs.

How long did it take for life to begin and evolve to cyanobacteria?
A. Lazcano & S.L. Miller
Journal of Molecular Evolution 39(6): 546-554, December, 1994
Abstract: There is convincing paleontological evidence showing that stromatolite-building phototactic prokaryotes were already in existence 3.5 x 10(9) years ago. Late accretion impacts may have killed off life on our planet as late as 3.8 x 10(9) years ago. This leaves only 300 million years to go from the prebiotic soup to the RNA world and to cyanobacteria. However, 300 million years should be more than sufficient time. All known prebiotic reactions take place in geologically rapid time scales, and very slow prebiotic reactions are not feasible because the intermediate compounds would have been destroyed due to the passage of the entire ocean through deep-sea vents every 10(7) years or in even less time. Therefore, it is likely that self-replicating systems capable of undergoing Darwinian evolution emerged in a period shorter than the destruction rates of its components (less than 5 million years). The time for evolution from the first DNA/protein organisms to cyanobacteria is usually thought to be very long. However, the similarities of many enzymatic reactions, together with the analysis of the available sequence data, suggest that a significant number of the components involved in basic biological processes are the result of ancient gene duplication events. Assuming that the rate of gene duplication of ancient prokaryotes was comparable to today's present values, the development of a filamentous cyanobacterial-like genome would require approximately 7 x 10(6) years-or perhaps much less. Thus, in spite of the many uncertainties involved in the estimates of time for life to arise and evolve to cyanobacteria, we see no compelling reason to assume that this process, from the beginning of the primitive soup to cyanobacteria, took more than 10 million years.

Richard1366 · 12-18-2002, 12:34 PM

Evolution was not a serial process, it was a parallel process consisting of many branches starting new species and sub species. At the time when the first single cell animals evolved, the conditions were probably right for different types of single cell animals to evolve then to further evolve into the many branches of life.

RufusAtticus · 12-18-2002, 02:41 PM

Quote:

What *is* the timescale required for evolution?

A generation.

Doubting Didymus · 12-18-2002, 02:49 PM

Quote:

Originally posted by RufusAtticus:
<strong>

A generation.</strong>

Yes. Very clever.

Baloo · 12-18-2002, 06:30 PM

An analogy: a man has 28 timestamped photos of himself standing next to every 100th mile marker between New York City and Los Angeles, and the timestamps, which cannot be faked, indicate that he managed to travel from NYC to LA in 24 hours. He has a vehicle that is demonstratably capable of traveling at over 160 miles per hour.

A creationist skeptic says, "but it's not possible to drive from NYC to LA in 24 hours - such a trip would obviously have taken weeks." The "skeptic" then grabs a rope, ties it to the car, and valiantly pulls it five feet. "See," he says between gasps, "it took me five minutes to move the car five feet." *gasp* "QED".

Point being, abbynormal, the skeptic's incredulity did not make the timestamped photos go away. Similarly, what effect do you think your incredulity has on the mountains of timestamped photos (aka fossils) demonstrating that life did in fact get from organic soup to yours truly in just a hair under 5 billion years?

Nic Tamzek · 12-18-2002, 08:00 PM

If you read Weiner's book The Beak of the Finch you will discover that experimentally measured rates of evolutionary change (measured via the Darwin unit handily enough) are orders of magnitude higher than the rates recorded in the fossil record.

I.e., it's not evolutionary processes that make evolution slow, but more probably environmental stability (/cyclicity). Since radical environmental changes are known to have occurred in the past, however, this is not a problem. That rapid diversification tends to follow disasters like asteroid impacts, and that some examples of rapid morphological diversification are known today (cichilds, silverswords, etc.), it appears that "macroevolution" can readily occur in the 1,000-1,000,000 year range, a geological eyeblink, it just mostly doesn't because most environments most of the time have most of their niches occupied.

A good brief article on this:

<a href="http://www.calacademy.org/calwild/fall97/html/horizon.htm" target="_blank">http://www.calacademy.org/calwild/fall97/html/horizon.htm</a>

Quote:

Reznick's guppies appear to have evolved at least 10,000 times faster than rates of change inferred from fossils. Even Losos's lizards, which changed at rates up to 2,117 darwins(d), far exceed the rates estimated from the fossil record. In a 1983 Science paper, University of Michigan paleontologist Philip Gingerich found that fossil organisms yielded, for a given million-year period, an average rate of change of only 0.21 d for invertebrates and 0.12 d for vertebrates. With longer stretches of time the changes become less perceptible and the rates get even smaller. That indicates, Reznick says, that "The fossil record is biased in a way that makes changes seem slower than they really could be."

These guppy and anole results come in the midst of a debate about whether a single process presides over the day-to-day changes that populations of individuals undergo, microevolution, and macroevolution, the big-picture view from fossils of the comings, goings, and splitting of species through time. As Reznick says, "The question is whether or not we can explain the larger scale events of evolution in terms of what we can see and study."

Fossil evidence points to three recurring trends in macroevolution: stasis, or long periods with little or no change, punctuations of rapid change, and speciation. Twenty-five years ago, paleontologists Stephen Jay Gould, of Harvard University, and Niles Eldredge, of the American Museum of Natural History, proposed their theory of punctuated equilibrium to explain the abrupt appearance of species and long gaps between conspicuous changes in the fossil record. As part of this idea, they have emphasized the need to seek separate mechanisms behind macro- and microevolution, arguing that while natural selection influences the survival of individuals, it cannot account for large-scale change in the history of life. Instead, they hypothesized for macroevolution a distinct process called species selection, whereby successful species rapidly replaced their ancestors.

But Reznick and his co-authors believe the guppies challenge such an assertion. "Our work lends support to the argument that neither punctuations nor stasis requires special explanations beyond natural selection," says Reznick. And while their paper does not directly address this issue, Losos and colleagues conclude from the anoles that "macroevolution may just be microevolution writ large."

Gingerich also suspected as much in his earlier study. Though signs of microevolution may vanish within the wide swath of the fossil record, he nonetheless wrote that "A microevolutionary rate of 400d is sufficient to change a mouse into an elephant in 10,000 years."

More importantly than how they figure in such heady theoretical debates, however, is the plain fact that the guppy study, and perhaps the anole one, too, reveal natural selection to be a powerful force. Both studies show that, under the right circumstances, experiments about evolution can succeed outside the contrived setting of a laboratory, right in the rough-and-tumble wild.

Doubting Didymus · 12-18-2002, 08:10 PM

:tut:

That's what I would have said, only more clumsily.

12-18-2002, 08:56 AM	#1
AbbyNormal Regular Member Join Date: Nov 2002 Location: Flagstaff, AZ, USA Posts: 152	Timescale required for evolution I thought I'd throw this out to the brilliant members of this board. What are current thoughts on the notion that the earth isn't old enough for such biological diversity to have arisen from solely naturalistic processes? What is the timescale required for evolution? I'm having great difficulty finding information...I'm sure it's buried in talkorigins somewhere, I'm just having little luck finding it. Or maybe I'm just inept at searching. Thanks so much for any help! Regards, AbbyNormal

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12-18-2002, 12:23 PM	#3
Zadok001 Veteran Member Join Date: Nov 2002 Location: Two Steps Ahead Posts: 1,124	tgamble: If I'm interpretting correctly, this is a key issue. I've actually wondered about it myself. We have an ENORMOUS variety of life here on Earth. The question is, how many millions of years would be required for a single common ancestor to evolve into the variety we see today. (Obviously, the circular solution is to say "However long it's been since abiogenesis." But that's no good. We're looking for evidence for or against evolution, citing evolution is not a good way to do that.) Is that clearer?

12-18-2002, 12:29 PM	#4
Tim Thompson Regular Member Join Date: Sep 2000 Location: Pasadena, CA, USA Posts: 455	AbbyNormal: What is* the timescale required for evolution?* Here are two examples that seem to provide template answers for the question. They are not based on any a-priori bias regarding the age of the Earth. Rather, the timescales are derived directly from observed rats of molecular evolution. Since those timescales are well within the scope of the independently derived age of the Earth, and independently derived geologic time scales, they would seem to be consistent with our knowledge of nature. A molecular timescale for vertebrate evolution S. Kumar & S.B. Hedges Nature 392(6679): 917-920, April 30, 1998 Abstract: A timescale is necessary for estimating rates of molecular and morphological change in organisms and for interpreting patterns of macroevolution and biogeography. Traditionally, these times have been obtained from the fossil record, where the earliest representatives of two lineages establish a minimum time of divergence of these lineages. The clock-like accumulation of sequence differences in some genes provides an alternative method by which the mean divergence time can be estimated. Estimates from single genes may have large statistical errors, but multiple genes can be studied to obtain a more reliable estimate of divergence time. However, until recently, the number of genes available for estimation of divergence time has been limited. Here we present divergence-time estimates for mammalian orders and major lineages of vertebrates, from an analysis of 658 nuclear genes. The molecular times agree with most early (Palaeozoic) and late (Cenozoic) fossil-based times, but indicate major gaps in the Mesozoic fossil record. At least five lineages of placental mammals arose more than 100 million years ago, and most of the modern orders seem to have diversified before the Cretaceous/Tertiary extinction of the dinosaurs. How long did it take for life to begin and evolve to cyanobacteria? A. Lazcano & S.L. Miller Journal of Molecular Evolution 39(6): 546-554, December, 1994 Abstract: There is convincing paleontological evidence showing that stromatolite-building phototactic prokaryotes were already in existence 3.5 x 10(9) years ago. Late accretion impacts may have killed off life on our planet as late as 3.8 x 10(9) years ago. This leaves only 300 million years to go from the prebiotic soup to the RNA world and to cyanobacteria. However, 300 million years should be more than sufficient time. All known prebiotic reactions take place in geologically rapid time scales, and very slow prebiotic reactions are not feasible because the intermediate compounds would have been destroyed due to the passage of the entire ocean through deep-sea vents every 10(7) years or in even less time. Therefore, it is likely that self-replicating systems capable of undergoing Darwinian evolution emerged in a period shorter than the destruction rates of its components (less than 5 million years). The time for evolution from the first DNA/protein organisms to cyanobacteria is usually thought to be very long. However, the similarities of many enzymatic reactions, together with the analysis of the available sequence data, suggest that a significant number of the components involved in basic biological processes are the result of ancient gene duplication events. Assuming that the rate of gene duplication of ancient prokaryotes was comparable to today's present values, the development of a filamentous cyanobacterial-like genome would require approximately 7 x 10(6) years-or perhaps much less. Thus, in spite of the many uncertainties involved in the estimates of time for life to arise and evolve to cyanobacteria, we see no compelling reason to assume that this process, from the beginning of the primitive soup to cyanobacteria, took more than 10 million years.

12-18-2002, 12:34 PM	#5
Richard1366 Veteran Member Join Date: Sep 2000 Location: Northern Virginia Posts: 1,260	Evolution was not a serial process, it was a parallel process consisting of many branches starting new species and sub species. At the time when the first single cell animals evolved, the conditions were probably right for different types of single cell animals to evolve then to further evolve into the many branches of life.

12-18-2002, 06:30 PM	#8
Baloo Regular Member Join Date: Jun 2000 Location: St. Louis, MO Posts: 417	An analogy: a man has 28 timestamped photos of himself standing next to every 100th mile marker between New York City and Los Angeles, and the timestamps, which cannot be faked, indicate that he managed to travel from NYC to LA in 24 hours. He has a vehicle that is demonstratably capable of traveling at over 160 miles per hour. A creationist skeptic says, "but it's not possible to drive from NYC to LA in 24 hours - such a trip would obviously have taken weeks." The "skeptic" then grabs a rope, ties it to the car, and valiantly pulls it five feet. "See," he says between gasps, "it took me five minutes to move the car five feet." gasp "QED". Point being, abbynormal, the skeptic's incredulity did not make the timestamped photos go away. Similarly, what effect do you think your incredulity has on the mountains of timestamped photos (aka fossils) demonstrating that life did in fact get from organic soup to yours truly in just a hair under 5 billion years?

12-18-2002, 08:10 PM	#10
Doubting Didymus Veteran Member Join Date: Jul 2002 Location: East Coast. Australia. Posts: 5,455	:tut: That's what I would have said, only more clumsily.

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