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Re: [OriginsTalk] How come we teach....???

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  • atfsoccer@aol.com
    Pan thanks for taking the time to write such a clear and concise response to each of my questions. I find the presence of the trilobite in the early Cambrian
    Message 1 of 13 , Jun 1, 2003
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      Pan thanks for taking the time to write such a clear and concise response to each of my questions.

      I find the presence of the trilobite in the early Cambrian period(5oo may??) to be particularly puzzling.  It seems odd to such complexity of development (with its appendages) and complex sensory system (well developed "eyes")) suggesting a sophisticated neurologic system.

      With the "explosions" it seems odd that we would see the "lumpiness of the solar system or the universe for that matter verses diffuse dispersion of matter and energy


      With respect to DNA, again it seems that a fundamental principle of diversity of life an evolution is that we have to explain why the earliest one celled living eukaryotes with "a few genes or chromosomes" somehow managed through "evolution" top get to man and his 46 chromosome and several billion nucleotides.


      Pan had written: There are genes in DNA
      that, when active, cause various forms of cancer, cystic fibrosis,
      Parkinson's disease and a host of other problems.    Why would a
      designer include such genes?

      Andrew writes back:  Pan, I would have to say that God did not create the genes for the birth defects and illnesses and disease which you describe.  I would postulate that God created a perfect human Genome with Adam and Eve.  The problems seem to have occurred from mutations in the chromosomes (Down syndrome) or from genetic mutations (leading to breast cancer and cystic fibrosis)  These came about from mutations in the genome with loss of information's.  I do not think that we believe that these genes were always present and get turned on for some reason.



      Obviously you can tell, Pan< that I approach science form a creationist philosophy.
      I am not interested in teaching religion in the classroom but more interested in making sure the data or evidence is presented as fairly as possible.  Unfortunately as we are all human we bring our prejudices with us regarding "Yes I see God's hand in this or No there is no need for a God or creator to explain all this"

      Again thanks for putting forth the time and expertise you have. 
      PS Where do you teach and at what level.  Did you know Pi teaches science at a high school in Oklahoma? I am a physician in Toledo Ohio. There are genes in DNA
      that, when active, cause various forms of cancer, cystic fibrosis,
      Parkinson's disease and a host of other problems.    Why would a
      designer include such genes?

      Semper Paratus Andrew
      .
      Andrews comment to Dave:  I read your answers and thankyou for responding.  I was honestly disappointed in the majority of your answers where you response to my question was essentially "it is not true."  Andrew


    • atfsoccer@aol.com
      In a message dated 5/30/03 10:56:41 PM Eastern Daylight Time, piasan@aol.com ... Andrews response to Pi: Pi I truly appreciate the frustrations of being a
      Message 2 of 13 , Jun 1, 2003
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        In a message dated 5/30/03 10:56:41 PM Eastern Daylight Time, piasan@... writes:

        In a message dated 5/30/03 7:21:14 PM Central Daylight Time, atfsoccer@... writes:

        How come we teach our students the "data" consistent with evolution but do not present the "data" which is contrary or at least less consistent?

        1.  How come we do not teach our students that human DNA has over 3 billion letters (nucleotides) and that each had to be added one to the next by "natural selection" starting from "scratch" according to evolution theory?


        Pi:
        Maybe because this statement contains at least two errors:
        1) Nucleotides are not added by natural selection.
        2) They to not need to be added one at a time.  Copy errors and polypoly can add whole sections in a single event.

        High school students understand, at a minimum, that DNA changes by mutation not natural selection.  I assure you of that.  If they didn't, they missed a lot of test questions.


        Andrews response to Pi: Pi I truly appreciate the frustrations of being a teacher.  My original plan in life was to teach high school math or biology but unfortunately that did not work out.  I do have three teens in high school so I can relate to your teaching frustrations wrt time etc.


        Andrew:
        2. How come we do not teach our students that DNA is not just a long chemical compound but highly ordered specific information. and that highly ordered, complex, specific information in every other field of science means one thing .... DESIGN (ex. SETI research)


        Pi:
        Because we don't teach information theory in biology.  Don't get too worked up over it, though .... we don't spend any time on SETI either.



        Andrew responds:  You see my point however Pi.  We intuitively recognize design. That is not necessarily scientific but by example SETI  is geared to look beyond the noise for some type of "pattern".  I am suggesting that if we applied the principles of SETI to DNA structure one would see it as designed information.



        Andrew:
        3.  How come we dot teach our students that a billion monkeys typing for a billion years will never type the first page of Shakespeare.  There will be lots of disorder and broken type writers and lots of monkey poop everywhere, however.


        Pi:
        Because typing is not included in biology.  ;-)


        Andrew responds: Point well made. The next thing you will probably be telling us is that monkeying around in the class is not allowed either?




        Andrew:
        4.  How come we dot teach our students that complex creatures suddenly appeared 500 million years ago in the "Cambrian explosion" and we dot have an evolutionary explanation for them?


        Pi:
        Students are taught that evolution can't presently answer lots of things.  Example:  evolution can't presently explain exactly how life started.  <shrug>



        Andrew response:  Where I am going with this Pi is to see why we have such complicated organisms as the trilobite (I think the largest deposits of them are actually here in a quarry in Toledo.  People come from miles around to dig them up)
        "appear" 500 million years ago with a relatively highly sophisticated structure and nervous system and apparently quite a compacted "eye" without any real pre Cambrian evidence of development.  In other words did the trilobite evolve or it just happens to be at the bottom of the Noaic Flood (Is Noaic even a word?)


        Andrew:
        5.  Why do we not teach our students that the chirality of proteins, amino acids (L) and DNA RNA (D) is difficult to explain with "evolutionary theory"



        Pi:
        Chilarity isn't even mentioned in high school biology.  These kids have enough trouble remembering that proteins are made of amino acids.


        Andrew respoinds:  I can appreciate that as well.  In med school I thought "chirality" had to do with whiter or not you were right handed or left handed or ambidextrous?
          But ofr the sake of argument you would think that in the primal slime we would be seeing fairly equal racemic mixtures fo all thes prebiotic chemicals. 



        Andrew:
        6. Why did we not teach our students that there is no evidence of any "explosions in nature or the lab leading to order" yet we have no problem suggesting the Big Bang Hypothesis??

        Pi:
        Maybe because the BB isn't an "explosion" in the normal use of the term.  BTW, the BB isn't a "hypothesis", it's the well accepted scientific theory of the origin of the universe that has predictive value and some of the predictions have been confirmed.




        Below, you bring up teaching kids "analytical thinking".  OK .... The section of my physical science textbook on the universe, the size of the universe is discussed and it is mentioned that we can see objects that are 12 billion light years away.  State standards REQUIRE that I teach the life cycle of stars takes millions of years.

        Now, give me the "analytical thinking" I should present to demonstrate that the universe is not a minimum of 12 billion years old.  Is it going to consist of: "God made the universe with the appearance of great age"?  I hope not.


        Andrews response: Pi as far as I can tell all of the data at least form astronomy does seem to indicate a universe of 12 billion years give or take a billion.  Leave the teaching of Genesis to me in the Church schools.  One expects the bias of creationism there.  I am advocating that there be no philosophical  bias (atheism Vs theism) in the classroom (ideally yes, practically speaking I know it is impossible)



        Andrew:
        9.If we are teaching science why do we teach that sedimentary rock if formed over "billions of years" (totally consistent with old earth and evolution) but fail to teach that sedimentary rock appearing to be millions of years old can be laid down in hours as seen in the geology around Mt. Hellions?



        Pi:
        We don't state a time period for the formation of sedimentary rock.  At least, my textbook doesn't.



        Andrew responds: Again Pi what I am looking for here is "Can we really say that sedimentary layers and fossil records were laid down over the past 3 billion years or were they the result of "catastrophic circumstances such as a global flood" thousands of years ago.  I know there is "no evidence" for a global flood from what I have heard form our friends here but recall yourself saying that "Students are taught that evolution can't presently answer lots of things.  Example:  evolution can't presently explain exactly how life started." 

         


        Andrew:
        10.Why dont we teach our students that the lower 4/5s of the earths crust has no fossils and most of them in an advanced stage (ie jellyfish, trilobite, uchins)of evolution the first time they appear.



        Pi:
        If it helps, in my school, fossils aren't mentioned on physical science (9th grade) except for what kind of rock is likely to contain them.  (Sedimentary, by the way.) In biology, they are mentioned only to the extent that they are the remains of  long dead animals.  We spend less than a class period on fossils... and much of that time is spend discussing things like the law of superposition, relative dating, and absolute dating.


        Andreww responds  Hey I thought you were a scence teacher now your are teaching about sthe social norms of dating?  And how exactly do the sooners of Oklaholma feel about dating their relatives? : )



        Andrew:
        Are we really teaching science and presenting all the facts to our students and letting them draw their own conclusions or are we presented the data consistent with the hypothesis
        that people with a particular agenda (atheism) want? 



        Pi:
        Sorry, Andrew, we teach neither atheism nor theism in science classes.  We teach science.


        Andrew concluding comment:
        Pi I know that you are a teacher of quality and integrity from the character of your responses.  But it may be overly idealistic to not think that there are people in both the academic world and the ecclesiastical world who are interested in eliminating the God of the Bible and replacing Him with the God of Intellect   Do you know what I mean?



        It's good to know that Catholics, Methodists, Lutherans, Episcopalians, Presbyterians, and Greek Orthodox have a "particular agenda (atheism)".  Maybe you would like to look at the list of those who have supported the teaching of  evolution "atheism".

        Sorry, Andrew, it is not the role of science to push either theism or atheism.  Individual scientists may profess their personal beliefs and support them with whatever rationale they wish .... but that is not the same as SCIENCE doing it.


        Andrew adds:  OhOh I am starting to write like you PI at least in color.  Agreed science by itself is pure and unbiased but it is the interpretation of the raw data or evidence that we bring our prejudices too.  For instance I am sure you will find this quote troubling:
               "If a C-14 date supports our theories,we put it in the main text.  If it does not entirely contradict them, we put it in a footnote. And if it is completely "out of dat," we just drop it."   Ingrid Olssson  Physicicist "C-14 dating and Egyptioan Chronology"
              

        At the High School level, we introduce them to the fundamental concepts, give them a few "gosh ! !   wow ! !" experiments, and a basic introduction to mainstream science.  Hopefully, they will be interested enough to pursue some real knowledge when they go on to college.


        Andrw comments:  My concern is Pi that even in the higher levels beyond HS are we really presenting our student with all the raw data on both sides of the evolution hypothesis or just giving the supporting data?



        Andrew:
        It seems like those concerned with the education of students and teaching the principles of analytical thinking would be concerned to present all the data and allow the students to draw their own conclusions.  Many of those students may say that just maybe natural evolution does not consistently explain all the data and just perhaps another model might?



        Pi:
        You want to know "how come" and "why" and "why not" .... OK.  You asked for it.



        I am highly concerned with teaching the "principles of analytical thinking".  Unfortunately, the kids should have learned that in 5th or 6th grade.  My lowest class is 9th grade.  The "principles of analytical thinking" is something I shouldn't be concerned with teaching .... they should KNOW them by the time I see them.  The "principles of analytical thinking" is something with which too damn few current high school students have any familiarity.

        So, lets get this right and put the situation in the real world classroom in perspective. 


        Andrew comments:  My 17 year old son asks me why he has to learn and memorize Chemistry and calculus etccand how it will ever be helpful to him in real life My standard answer is that much of what we learn may not be all that helful some day but the anlaytical thinking that goes along with it is what we carry over to helping us solve the everyday problems in real life.  I still have no idea what differnetnial equations are used for and took it for a semester and probalbly got an A it it.  Unfortuantaley Calculus ranks right up there too!



        When I went to high school, lab classes (biology, chemistry, physics) were two class periods ... one for class and one for lab.    Now those courses are one class period.  Not only that, but due to advances in science, considerable material has been added to the curriculum ... things like DNA, genetics, and molecular biology ... the existence of which is not in dispute. 

        So, in half the time, I'm supposed to cover about 30% more material (including drug-resistance, pregnancy avoidance, etc.) AND information theory AND the skills they need to understand information theory AND fundamental skills they are already supposed to have, then add on to that time teach still additional "models".

        R R R i i i g g g h h h t t t . 

        (I'd put in a joke about what you've been smoking, but someone would take it the wrong way.)

        Andrew, anytime you want to discuss the actual details of the curriculum that is REALLY taught instead of some ill-informed pie-in-the-sky version of what they THINK is taught, I'll be happy to oblige.  Last year I used the HR. textbook.  See if you can get a copy and lets compare notes.  BTW, this year, we covered only 2 of the 5 chapters on evolution,  and we never even got to the chapter on human evolution.

        Andrew
        More tomorrow,


        Pi:
        I'll be looking forward to it.

        Pi good conversing with you.  I will narrow it down some.  I w as just stirring up the pot a little.     Andrew
      • Philip Nicholls
        ... While trilobites did indeed appear in the early cambrian their heyday occurred during the late cambrian/early ordovician, during which time there were
        Message 3 of 13 , Jun 1, 2003
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          In a blinding flash of insight atfsoccer@... wrote:

          >Pan thanks for taking the time to write such a clear and concise response to
          >each of my questions.
          >
          >I find the presence of the trilobite in the early Cambrian period(5oo may??)
          >to be particularly puzzling. It seems odd to such complexity of development
          >(with its appendages) and complex sensory system (well developed "eyes"))
          >suggesting a sophisticated neurologic system.

          While trilobites did indeed appear in the early cambrian their
          "heyday" occurred during the late cambrian/early ordovician, during
          which time there were more than sixty familes.

          Complexity of body form can be misleading. Both the eye and the
          bodyplan seem to be repetition of a general theme and this is one of
          the reasons I like the hox gene hypothesis for explaining the cambrian
          event.

          >With the "explosions" it seems odd that we would see the "lumpiness of the
          >solar system or the universe for that matter verses diffuse dispersion of matter
          >and energy

          The lumpiness of the universe suggests that there is more matter out
          there than we are aware of and that most of this matter does not
          interact with light ( so-called "dark matter"). Does dark matter
          exist? Stay tuned.

          >With respect to DNA, again it seems that a fundamental principle of diversity
          >of life an evolution is that we have to explain why the earliest one celled
          >living eukaryotes with "a few genes or chromosomes" somehow managed through
          >"evolution" top get to man and his 46 chromosome and several billion nucleotides.

          Some species of bananna have 55, 77 or 88 chromsomes. The black
          mulberry tree has 308. The arabian camel has 70. Catfish have 58.
          The king crab has 208. Plants in particular are able to double,
          sometimes triple chromsome numbers in a few generations. Yet,
          interestingly, all species of old world monkeys have the same
          chromsome number (44) while all great apes have 48 chromosomes. Yet if
          you check on the number of nucleotides you find that the differences
          between old world monkeys,apes and humans is not that great

          >Pan had written: There are genes in DNA
          >that, when active, cause various forms of cancer, cystic fibrosis,
          >Parkinson's disease and a host of other problems.    Why would a
          >designer include such genes?
          >
          >Andrew writes back: Pan, I would have to say that God did not create the
          >genes for the birth defects and illnesses and disease which you describe. I
          >would postulate that God created a perfect human Genome with Adam and Eve. The
          >problems seem to have occurred from mutations in the chromosomes (Down syndrome)
          >or from genetic mutations (leading to breast cancer and cystic fibrosis)
          >These came about from mutations in the genome with loss of information's. I do
          >not think that we believe that these genes were always present and get turned
          >on for some reason.

          I would submit that it is a less than perfect Genome if it can mutate
          in this fashion. Why not create genes that don't mutate or that when
          they mutate they only do so in benificial fashions?


          >Obviously you can tell, Pan< that I approach science form a creationist
          >philosophy.
          >I am not interested in teaching religion in the classroom but more interested
          >in making sure the data or evidence is presented as fairly as possible.
          >Unfortunately as we are all human we bring our prejudices with us regarding "Yes I
          >see God's hand in this or No there is no need for a God or creator to explain
          >all this"

          I would have to say that very few biology teachers would tell there
          classes that there is not need for God. However, accepting that
          evolution has occurred, continues to occur is is the central unifying
          concept of modern biology does not require you to abandon belief in
          God.

          The differece is that I don't want biology teachers teaching my
          children about God. I don't think you do either.


          >Again thanks for putting forth the time and expertise you have.
          >PS Where do you teach and at what level. Did you know Pi teaches science at
          >a high school in Oklahoma? I am a physician in Toledo Ohio.

          I teach biology, chemistry and physics in upstate New York.




          Semper Allouata
        • piasan@aol.com
          In a message dated 6/1/03 6:38:57 PM Central Daylight Time, atfsoccer@aol.com ... Pi: We try not. But these kids are just discovering hormones. ... Pi: You ve
          Message 4 of 13 , Jun 1, 2003
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            In a message dated 6/1/03 6:38:57 PM Central Daylight Time, atfsoccer@... writes:


            Andrew:
            3.  How come we dot teach our students that a billion monkeys typing for a billion years will never type the first page of Shakespeare.  There will be lots of disorder and broken type writers and lots of monkey poop everywhere, however.


            Pi:
            Because typing is not included in biology.  ;-)



            Andrew responds: Point well made. The next thing you will probably be telling us is that monkeying around in the class is not allowed either?


            Pi:
            We try not.  But these kids are just discovering hormones.


            <snip>
            Andrews response: Pi as far as I can tell all of the data at least form astronomy does seem to indicate a universe of 12 billion years give or take a billion.  Leave the teaching of Genesis to me in the Church schools.  One expects the bias of creationism there.  I am advocating that there be no philosophical  bias (atheism Vs theism) in the classroom (ideally yes, practically speaking I know it is impossible)


            Pi:
            You've already seen Pan's comments on the issue:
            I would have to say that very few biology teachers would tell there
            classes that there is not need for God.   However, accepting that
            evolution has occurred, continues to occur is is the central unifying
            concept of modern biology does not require you to abandon belief in
            God.

            He's lucky.  He teaches in upstate New York where the climate is a bit more "evolution friendly".  I'm teaching in the Bible Belt, it is critical to me that these kids understand that science does NOT say there is no God.

            At the same time, the state standard for Biology requires the teaching of evolution... specifically "the evidence of common ancestry" (Oklahoma P.A.S.S. Biology Content Standard 3.1

            BTW, Pan ... I have Physical Science, Physics, Chemistry, and Biology (and MS Office).  Next year I hope to add C++ programing and Business Math.

            <snip>

            Pi:
            <snip> We spend less than a class period on fossils... and much of that time is spend discussing things like the law of superposition, relative dating, and absolute dating.



            Andreww responds  Hey I thought you were a scence teacher now your are teaching about sthe social norms of dating?  And how exactly do the sooners of Oklaholma feel about dating their relatives? : )


            Pi:
            No, no ... not "superior position" ... "superposition".

            As far as dating relatives ....you don't want to know.


            <snip>

            Andrew concluding comment:
            Pi I know that you are a teacher of quality and integrity from the character of your responses.  But it may be overly idealistic to not think that there are people in both the academic world and the ecclesiastical world who are interested in eliminating the God of the Bible and replacing Him with the God of Intellect   Do you know what I mean?


            Pi:
            I'm sure there are people in academic world who are interested in eliminating God.  There are also people in the academic world who are interested in promoting God.  Neither is appropriate to a public school classroom.... and the disciplinary action for doing so should be the same either way.


            <snip>
            Andrew adds:  OhOh I am starting to write like you PI at least in color.  Agreed science by itself is pure and unbiased but it is the interpretation of the raw data or evidence that we bring our prejudices too.  For instance I am sure you will find this quote troubling:
                  "If a C-14 date supports our theories,we put it in the main text.  If it does not entirely contradict them, we put it in a footnote. And if it is completely "out of dat," we just drop it."   Ingrid Olssson  Physicicist "C-14 dating and Egyptioan Chronology"


            Pi:
            Totally unprofessional... as presented.


                 
            Pi:
            At the High School level, we introduce them to the fundamental concepts, give them a few "gosh ! !   wow ! !" experiments, and a basic introduction to mainstream science.  Hopefully, they will be interested enough to pursue some real knowledge when they go on to college.


            Andrw comments:  My concern is Pi that even in the higher levels beyond HS are we really presenting our student with all the raw data on both sides of the evolution hypothesis or just giving the supporting data?


            Pi:
            I wouldn't know.  I will say this ... one recommendation that I make to EVERY student I know is going to college is that they should take a basic logic course their VERY FIRST semester no matter what schedule juggling they need to do to make it happen.

            <snip>

            Andrew comments:  My 17 year old son asks me why he has to learn and memorize Chemistry and calculus etccand how it will ever be helpful to him in real life My standard answer is that much of what we learn may not be all that helful some day but the anlaytical thinking that goes along with it is what we carry over to helping us solve the everyday problems in real life.  I still have no idea what differnetnial equations are used for and took it for a semester and probalbly got an A it it.  Unfortuantaley Calculus ranks right up there too!

            Pi:
            Calculus was a ... well, I better not use the word ....for me too.  I never had any trouble in math until I hit Calc.


            <snip>
            Pi good conversing with you.  I will narrow it down some.  I w as just stirring up the pot a little.     Andrew


            Pi:
            It did.   <grin>
          • Eric
            ...
            Message 5 of 13 , Jun 2, 2003
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              > Andrew responds:
              <<We intuitively recognize
              > design. That is not necessarily scientific but by example SETI is
              geared to look
              > beyond the noise for some type of "pattern". I am suggesting that
              if we
              > applied the principles of SETI to DNA structure one would see it as
              designed
              > information.
              >


              SETI doesn't just look for a pattern, because many perfectly natural,
              unintelligent sources generate patterns of radiowaves, such as
              rotating neutron stars. What they are looking for are patterns which
              cannot be explained by natural phenomena, such as a series of prime
              numbers or pi or e. If the principles we apply to the SETI project
              were applied to DNA then DNA would get a pass because we DO know how
              those patterns could be generated by natural, non-intelligent means.


              Take care,

              Eric
            • Eric
              ... have such ... deposits of them are ... to dig ... sophisticated ... without any real ... trilobite evolve ... even a ... Maybe this will help: A Review of
              Message 6 of 13 , Jun 2, 2003
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                > Andrew response: Where I am going with this Pi is to see why we
                have such
                > complicated organisms as the trilobite (I think the largest
                deposits of them are
                > actually here in a quarry in Toledo. People come from miles around
                to dig
                > them up)
                > "appear" 500 million years ago with a relatively highly
                sophisticated
                > structure and nervous system and apparently quite a compacted "eye"
                without any real
                > pre Cambrian evidence of development. In other words did the
                trilobite evolve
                > or it just happens to be at the bottom of the Noaic Flood (Is Noaic
                even a
                > word?)


                Maybe this will help:


                A Review of The Evidence For Trilobite Predecessors in the Fossil
                Record

                Robert B. MacNaughton, Ph.D. Candidate
                Department of Geological Sciences, Queen's University
                Kingston, Ontario, Canada, K7L 3N6


                This paper was published in the January issue of the Oregon
                Geological Society's newsletter.


                INTRODUCTION
                Skeletons of trilobites, an extinct group of arthropods, first appear
                in the fossil record in rocks of Early Cambrian age. Trilobites were
                among the earliest organisms to possess a well- mineralized
                exoskeleton, and are sufficiently common in rocks of Cambrian age
                that the Cambrian Period is sometimes informally referred to as "The
                Age of Trilobites". While trilobites are indeed a typical fossil in
                Cambrian deposits, the lineage continued for approximately 300
                million years, finally becoming extinct at the end of the Permian
                Period. A very accessible introduction to these fascinating organisms
                (as well as many pointers to more technical literature) can be
                obtained from Ricardo Levi-Setti's (1993) book Trilobites.
                Interpreting the early history of trilobites is a complex task. The
                first appearance of skeletal faunas is diachronous during the Early
                Cambrian (Brasier, 1989). That is, the faunas first appeared during
                slightly different time intervals at different places around the
                world. Another difficulty is that trilobite faunas show marked
                provinciality during this interval (Cowie, 1971; Brasier, 1989). This
                means that different parts of the world were characterized by
                different genera of trilobites, a pattern also typical of many modern
                groups of organisms. Additionally, there is evidence that some
                patterns of first appearance are probably due to facies control
                (Mount and Signor, 1992). Simply stated, facies control means that
                some types of sedimentary rock preserve shelly fossils better than
                others. Despite these difficulties, the early history of trilobites
                is becoming increasingly well understood (Brasier, 1989; Briggs and
                Fortey, 1992).

                Certain creationists have pressed the allegation that the fossil
                record contains no evidence of predecessors or ancestors to
                trilobites and that the "abrupt" first appearance of trilobites is
                thus positive evidence for the instantaneous creation of the lineage.
                However, this assertion is plainly untenable if the fossil record is
                examined in more than a cursory manner. The Early Cambrian was a time
                when numerous taxa, including the arthropods, attained mineralized
                skeletons (Lipps and Signor, 1992); any soft-bodied ancestors of
                these taxa would have had little chance for preservation as fossils.
                (While soft-bodied organisms can be preserved under exceptional
                conditions, these conditions are very rare. Normally, it is only the
                hard-parts of organisms that are preserved as fossils.) Nonetheless,
                the fossil record does offer two lines of direct evidence that point
                to the existence of trilobite predecessors.


                EVIDENCE FROM TRACE FOSSILS
                The first line of evidence comes from trace fossils, the preserved
                tracks, trails, and burrows of living organisms. Marine sedimentary
                rocks of many different ages (Cambrian to Permian) have been found to
                contain a very distinctive suite of burrows, scratch-marks and
                furrowing traces that can confidently be ascribed to the activitites
                of trilobites (Seilacher, 1970; Crimes, 1973). Indeed, rare specimens
                have been found which contain trilobite body fossils within the
                burrows (Osgood, 1970). In sections of rock that span the boundary
                between the Cambrian and the preceding Vendian Period, these
                distinctive trace fossils are commonly found in strata which are
                lower stratigraphically (and thus older) than those containing the
                first preserved trilobite skeletons (Crimes, 1987, 1994). Non-
                existent organisms cannot produce burrows, and so these trace fossils
                demonstrate that trilobites, or their ancestors, did in fact exist
                prior to the first appearance of trilobite body fossils. Even more
                intriguing is the observed fact that these trace fossils become
                increasingly more complex with time during the period preceding the
                advent of mineralized skeletons (Crimes, 1992). This implies that the
                behaviors of these ancestral trilobites were evolving.
                EVIDENCE FROM THE PRECAMBRIAN FOSSIL RECORD
                The second line of evidence comes from the fortuitously preserved
                soft-bodied organisms of the latest Precambrian-aged (Vendian)
                Ediacaran Fauna. The Ediacaran Fauna were traditionally interpreted
                as ancestral representatives of and predecessors to taxonomic groups
                which occur more abundantly in the Cambrian Period (Glaessner, 1984;
                Fedonkin, 1985). This view was challenged by Seilacher (1984, 1989),
                who argued that the Ediacaran Fauna were not animals but instead were
                a group of structurally unique organisms belonging to a previously
                unrecognized kingdom, dubbed the Vendozoa. Seilacher's hypothesis has
                been vigourously debated (Gehling, 1991; Fedonkin, 1992; Conway
                Morris, 1993; Crimes et al., 1995) and Seilacher himself seems to
                have moved away from his earlier hypothesis (Buss and Seilacher,
                1994). The present consensus is apparently that while the Vendozoan
                hypothesis may apply to some Ediacaran organisms, it does not apply
                to them all. Certainly, representatives of several extant phyla have
                been convincingly documented (Gehling, 1987, 1988, 1991; Fedonkin,
                1992).
                The organisms represented in the Ediacaran fauna were soft-bodied and
                are preserved as impressions, generally (but not exclusively) on the
                soles (bottoms) of sandstone beds. They were apparently preserved as
                the result of the fortuitous sediment-binding action of microbial
                mats (Gehling, 1991; Seilacher and Pfluger, 1994). In Gehling's
                (1991, p. 218) view, these microbial mats "acted both to erosion
                proof the substrates occupied by organisms buried under storm sands,
                and to initiate immediate mineral encrusting of organic surfaces and
                cementataion of the sand at the interface." (The interface referred
                to is the one between layers of sediment.) This mode of preservation
                seems to have been confined to the Precambrian--it was presumably
                curtailed by the activities of microbe-eating burrowing and grazing
                organisms which appeared in the latest Precambrian and early Cambrian
                (Gehling, 1991; Crimes, 1992, 1994).

                The Ediacaran Fauna contains several species which may represent, if
                not ancestral trilobites, then at least ancestral arthropods. These
                include such taxa as Vendia, Vendomia, Onega, Praecambridium,
                Parvancorina, and Marywadea (Gehling, 1991; Fedonkin, 1992; Jenkins,
                1992). All of these genera show well-developed head and tail
                differentiation and possess body outlines such as might be expected
                in a primitive arthropod. There is one additional taxon, yet to be
                formally described, which shows great promise to elucidate the early
                history of the trilobites. It has been described in the following
                terms by Gehling (1991, p. 206):

                A new metameric form . . . features a head end with a symmetrically
                placed D- shaped ridge. The ridge parallels the front margin, and
                seems to contain a domed area within. The body has a raised axial
                zone, and segments that show evidence of articulation . . . This
                organism has more external resemblance to the trilobites than any
                form so far described from the Ediacara assemblage.
                The photograph which Gehling provides (Plate 4, Fig. 4) definitely
                supports his last assertion. The same taxon has also been described
                in more detail by Jenkins (1992), who dubs it a "soft- bodied
                trilobite" and states that, "Its observed characteristics occur in a
                variety of Paleozoic trilobites, but it can probably be considered to
                differ from all known forms at the ordinal level" (p. 169). Jenkins
                (1992, Figure 15) figures sketches of several specimens of the
                organism; like Gehling's photograph, they show an organism strongly
                resembling a trilobite.


                CONCLUSION
                The fossil record provides a significant amount of evidence for the
                existence of trilobites prior to their aquisition of a mineralized
                skeleton. Trace fossils offer a record of the evolving behavior of
                the soft-bodied ancestral trilobites, while material in the Ediacaran
                Fauna indicates the presence of probable primitive arthropods and
                likely presence of ancestral trilobites in the latest Precambrian.
                Assertions that trilobites appear "instantaneously" in the rocks of
                the Cambrian System, without any sign of ancestral forms, are plainly
                incorrect.

                ACKNOWLEDGEMENTS
                My thanks to Andrew MacRae for reviewing an earlier version of this
                document, and to Russell Stewart for converting it to HTML.

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