Cambrian Explosion
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You have certainly heard of the Cambrian explosion. It is used to describe the sudden appearance of a huge variety of fossil organisms with hard skeletons at the beginning of the Cambrian Period. http://en.wikipedia.org/wiki/Cambrian_Explosion What are the most plausible explanations you know? If it is some form of strong emergence, there must be a code behind it, a code which specifies the spatial organization of the body and the body plan for complex organisms with hard shells and skeletons. Since the body is formed during the embryonic development, it must be an embryonic development code, a recipe for builing multicellular structures. How does this code look like ? Is it similar to fractals and iterated function systems (IFS) ? Is it more related to the 4-symbol alphabet of the genetic code, to the 20-symbol protein alphabet, or more to cell types (possibly attractors of genetic regulatory networks) ? -J. |
Cambrian Explosion
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Here is a novel interpretation from Jorge Herkovitz, first talked to him
about this at a Society for Environmental Toxicology and Chemistry conference in 2001. http://www.findarticles.com/p/articles/mi_m0CYP/is_12_109/ai_82551842 >From the first paragraph I pasted the following: Present-day biodiversity, estimated to comprise more than 100 million species, has developed in around 4,000 million years on the basis of the ability of life forms to adapt and multiply at a rate that surpassed extinctions. Species, including humans, depend on the ecosystems that have operated with no or minimal human intervention up to recent years. Recent extinction rates are 100-1,000 times their pre-human levels in taxonomically diverse groups from widely different environments. Moreover, it is accepted that if all species currently endangered become extinct, then future extinction rates will be 10 times recent rates (1). Although chemicals are the basic units for the development of life, it seems meaningful to take into account Paracelsus' statement that "all things are poison and nothing is without poison." From this perspective it seems obvious that chemical and physical features have been considered driving forces of evolutionary processes from the beginning of recorded history. Estimates suggest that the current world production of chemicals is 400 million metric tons. Almost 11 million naturally occurring or man-made chemicals have been identified in the CAS Registry File, although only a small portion of them is commercially available. I would like to present the hypothesis of a direct link between chemical stress and a major mass extinction process, the Cretaceous-Tertiary (C-T) event, with the aim of providing a more holistic view on the potential of chemical stress on the evolutionary process. Lou ----- Original Message ----- From: "Jochen Fromm" <[hidden email]> To: "'The Friday Morning Applied Complexity Coffee Group'" <Friam at redfish.com> Sent: Monday, March 13, 2006 4:21 AM Subject: [FRIAM] Cambrian Explosion > > You have certainly heard of the Cambrian explosion. > It is used to describe the sudden appearance of a > huge variety of fossil organisms with hard skeletons > at the beginning of the Cambrian Period. > http://en.wikipedia.org/wiki/Cambrian_Explosion > > What are the most plausible explanations you know? > If it is some form of strong emergence, there must be > a code behind it, a code which specifies the spatial > organization of the body and the body plan for complex > organisms with hard shells and skeletons. > > Since the body is formed during the embryonic > development, it must be an embryonic development > code, a recipe for builing multicellular structures. > How does this code look like ? Is it similar to fractals > and iterated function systems (IFS) ? Is it more related > to the 4-symbol alphabet of the genetic code, to the > 20-symbol protein alphabet, or more to cell types > (possibly attractors of genetic regulatory networks) ? > > -J. > > > ============================================================ > FRIAM Applied Complexity Group listserv > Meets Fridays 9a-11:30 at cafe at St. John's College > lectures, archives, unsubscribe, maps at http://www.friam.org > |
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There is no doubt that environmental changes and chemical/physical stress are among the causes for the Cambrian explosion (Snowball Earth, glaciation, etc.). Certainly there is a connection between "emergence" and "extinction", between complexity and catastrophes. My question was more about the "how" (how does the underlying code define the development of individuals? is there such a code for the body plan?) and less about the "why". The form or "architecture" of plants for example can be described well by fractals, IFS and L-Systems. Skeletons and animal bodies have a certain amount of self-similarity, too: a typical modern animal body has a certain amount of limbs (2-6 legs or arms), and each limb has further sub-limbs (2-6 toes or fingers). Therefore it must be possible to describe bodies and their development with simple iterative rules. I wonder what kind of rule set or code is really used? The "three-lobed" trilobite for example, one of the first animals that appeared in the Cambrian period has a very simple repetitive head-body/thorax-tail structure, where the body is composed of many similar repetitive segments. http://en.wikipedia.org/wiki/Trilobite -J. |
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You might find these references helpful:
Muller and Newman, Origination of Organismic Form. Peterson and Parker, Ecological Scale. Kalona and Lamb, Evolution in Four Dimensions. Gould, Ontogeny and Phylogeny. McNamara, Shapes of Time. Edelman. Topobiology: An Introduction to Molecular Embryology. Gus Koehler, Ph.D. Principal Time Structures 1545 University Ave. Sacramento, CA 95825 916-564-8683, Fax: 916-564-7895 Cell: 916-716-1740 www.timestructures.com -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of Jochen Fromm Sent: Monday, March 13, 2006 11:13 AM To: 'The Friday Morning Applied Complexity Coffee Group' Subject: Re: [FRIAM] Cambrian Explosion There is no doubt that environmental changes and chemical/physical stress are among the causes for the Cambrian explosion (Snowball Earth, glaciation, etc.). Certainly there is a connection between "emergence" and "extinction", between complexity and catastrophes. My question was more about the "how" (how does the underlying code define the development of individuals? is there such a code for the body plan?) and less about the "why". The form or "architecture" of plants for example can be described well by fractals, IFS and L-Systems. Skeletons and animal bodies have a certain amount of self-similarity, too: a typical modern animal body has a certain amount of limbs (2-6 legs or arms), and each limb has further sub-limbs (2-6 toes or fingers). Therefore it must be possible to describe bodies and their development with simple iterative rules. I wonder what kind of rule set or code is really used? The "three-lobed" trilobite for example, one of the first animals that appeared in the Cambrian period has a very simple repetitive head-body/thorax-tail structure, where the body is composed of many similar repetitive segments. http://en.wikipedia.org/wiki/Trilobite -J. ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org |
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In reply to this post by Jochen Fromm-3
As I understand it, repetition of units is controlled by the homeobox
gene, one of the earliest "meta" gene. The mechanism is essentially unchanged between fruit flys and humans. The appearance for the first time of a gene that controlled genetic expression just prior to the Cambrian is about as good an explanation of the Cambrian explosion as any I've heard. Basically, the event is still a mystery. Cheers On Mon, Mar 13, 2006 at 08:13:11PM +0100, Jochen Fromm wrote: > > There is no doubt that environmental changes and > chemical/physical stress are among the causes for the > Cambrian explosion (Snowball Earth, glaciation, etc.). > Certainly there is a connection between "emergence" > and "extinction", between complexity and catastrophes. > My question was more about the "how" (how does the > underlying code define the development of individuals? > is there such a code for the body plan?) and > less about the "why". > > The form or "architecture" of plants for example can > be described well by fractals, IFS and L-Systems. Skeletons > and animal bodies have a certain amount of self-similarity, > too: a typical modern animal body has a certain amount of limbs > (2-6 legs or arms), and each limb has further sub-limbs > (2-6 toes or fingers). Therefore it must be possible to > describe bodies and their development with simple iterative > rules. I wonder what kind of rule set or code is really used? > > The "three-lobed" trilobite for example, one of the first > animals that appeared in the Cambrian period has a very > simple repetitive head-body/thorax-tail structure, where the > body is composed of many similar repetitive segments. > http://en.wikipedia.org/wiki/Trilobite > > -J. > > > ============================================================ > FRIAM Applied Complexity Group listserv > Meets Fridays 9a-11:30 at cafe at St. John's College > lectures, archives, unsubscribe, maps at http://www.friam.org -- *PS: A number of people ask me about the attachment to my email, which is of type "application/pgp-signature". Don't worry, it is not a virus. It is an electronic signature, that may be used to verify this email came from me if you have PGP or GPG installed. Otherwise, you may safely ignore this attachment. ---------------------------------------------------------------------------- A/Prof Russell Standish Phone 8308 3119 (mobile) Mathematics 0425 253119 (") UNSW SYDNEY 2052 R.Standish at unsw.edu.au Australia http://parallel.hpc.unsw.edu.au/rks International prefix +612, Interstate prefix 02 ---------------------------------------------------------------------------- |
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I have heard of Hox genes before, but not in the context of the Cambrian Explosion. Looks like it is associated with the evolution of Hox genes. Wikipedia says Hox and "homeobox" genes are closely related to the body plan. They are labels and markers, i.e. they assign the right identity to particular body regions along the body axis (individual hox genes are activated at different positions), but they also control the development. This means they represent and control the structure of the body at the same time, just like the emotions (as we know from Psychology) signal the state of the body and control the body at same time. http://en.wikipedia.org/wiki/Homeobox Does this mean that the code for embryonic development is related to "meta" genes (transcription factors which typically switch on cascades of other genes) ? Interesting. The hox genes are therefore perhaps a code in a code ? Changes in Hox gene number results in different phyla and body plans, changes in Hox gene expression in slightly modulated body plans with different numbers of segments, and subtle changes in the details of a Hox transcription pattern results in modified segments, see the following article about "Shaping animal body plans in development and evolution by modulation of Hox expression patterns" http://www3.interscience.wiley.com/cgi-bin/abstract/34221 http://wwworm.biology.uh.edu/evodevo/lecture18/gellon98.pdf -J. |
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The book "The Art of Genes" talks about a lot of this stuff, including
Hox and momeobox genes. It's a book for the educated lay person, doesn't requre a background in biology. - Martin Jochen Fromm wrote: > I have heard of Hox genes before, but not in the context > of the Cambrian Explosion. Looks like it is associated with > the evolution of Hox genes. Wikipedia says Hox and > "homeobox" genes are closely related to the body plan. They > are labels and markers, i.e. they assign the right identity > to particular body regions along the body axis (individual > hox genes are activated at different positions), but they > also control the development. This means they represent and > control the structure of the body at the same time, just > like the emotions (as we know from Psychology) signal the > state of the body and control the body at same time. > http://en.wikipedia.org/wiki/Homeobox > > Does this mean that the code for embryonic development is > related to "meta" genes (transcription factors which > typically switch on cascades of other genes) ? Interesting. > The hox genes are therefore perhaps a code in a code ? > Changes in Hox gene number results in different phyla > and body plans, changes in Hox gene expression in slightly > modulated body plans with different numbers of segments, and > subtle changes in the details of a Hox transcription > pattern results in modified segments, see the following > article about "Shaping animal body plans in development > and evolution by modulation of Hox expression patterns" > http://www3.interscience.wiley.com/cgi-bin/abstract/34221 > http://wwworm.biology.uh.edu/evodevo/lecture18/gellon98.pdf > > -J. > > > ============================================================ > FRIAM Applied Complexity Group listserv > Meets Fridays 9a-11:30 at cafe at St. John's College > lectures, archives, unsubscribe, maps at http://www.friam.org |
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