The Origin of Form Was Abrupt Not Gradual is an article by Suzan Mazur which is focused on the views of cellular biologist Stuart Newman. Suzan Mazur writes:

…Stuart Newman's now got a seductive theory about the origin of form of all 35 or so animal phyla–"it happened abruptly" not gradually, roughly 600 million years ago via a "pattern language"–which serves as the centerpiece of the "Extended Synthesis." That's the reformulation of the Modern Synthesis or neo-Darwinian theory of evolution kicked off this summer at Konrad Lorenz Institute in Altenberg, Austria by 16 scientists I dubbed "the Altenberg 16."

The impetus for the Extended Synthesis, a graft onto, or a major departure from, the Modern Synthesis (depending on who is describing it), was the overwhelming data generated in recent years that just didn't fit the old formula. Phenomena like self-organization, epigenetics and plasticity intruded in ways that were complementary to, and sometimes contradictory to, natural selection. Then there was niche construction to consider–where organisms invent their habitats (burrows, bird nests, bee hives, etc.) rather than being selected by their fitness to pre-existing ones. And also punctuated evolution, abrupt transitions in the fossil record, and the even more puzzling episodes of stasis.

While much of the evolutionary biology community resists the notion of an evolutionary framework that begins to consider the role of determinants beyond the gene, as the Extended Synthesis does, the momentum of the new synthesis is undeniable (see Google for "the Altenberg 16"). And there are other scientists and philosophers of science–avowed non-creationists–who say the Extended Synthesis does not go far enough in relegating natural selection to a reduced role.

Concerns about the role of natural selection and the recognition that origin "abruptness" calls for theoretical revisions is reflected in Newman's views. Newman discusses intriguing ideas including the "Extended Synthesis." He responds to a question:

We know that no new genes arose in conjunction with the vertebrate limb. Pre-existing genes were used in a new context. The limb bud is an outpocketing of the body wall. It came into existence as a result of slight changes in the surface of the embryo. This provided (by the action of some of the DPMs) a new "morphogenetic field," the limb bud, which served as the medium for a whole new set of self-organizing dynamics.

The time between establishing the limb bud and establishing the limb pattern was probably not very great. The second followed from the first fairly readily because of the self-organization that was mobilized when the new morphogenetic field appeared.

Continuous gradual changes in growth and shape can happen by the standard gradualist neo-Darwinian modes. But once the tissue reaches a critical size and shape, the genes that were already there start to interact with each other and the local physical environment in new ways because they're in a new context.

This happened in the limb bud 375 million or 400 million years ago and it happened in the animal body 200 million years before that. Something changed in the environment of the single-celled ancestors of modern animals or perhaps a minor genetic change occurred in several different cell populations. The result was clusters of cells where before you had only single cells. And we know that the genes that cause cells to cluster were present way before any cell clusters existed.

"Genes that cause cells to cluster were present way before any cell clusters existed"- now there's a front loading assertion. Then after describing how backbones form Newman makes this comment:

Genes don't tell the molecules to oscillate–genes specify the molecules the cells can produce and the molecules interact with each other and with the cells themselves. The non-linear actions and reactions among the molecules and cells, their production and their breakdown, cause them to oscillate with time. The genes are necessary components of these networks of interactions, but to say that it's the genes that make it all run is incorrect. You also can't have it happen without atoms but to say atoms "program" development is an absurdity–what philosophers call a "category mistake." What generate forms are the networks of molecular-cellular-physical interactions that occur within tissues, which we have decomposed into DPMs.

So networks of molecular-cellular interactions generate new forms? Read the article and get the context because Newman weighs in on Darwin too:

That represented progress in its own time–to look at very complex things and try to understand them on the basis of the simple effects that we know and understand. But Darwin wasn't entirely correct about this because organisms we encounter in today's world use very intricate, highly integrated genetic mechanisms to produce their forms, the so-called genetic programs for development. Such programs could not have existed when the simplest multicellular organisms first arose. But because the transition between single-cell ancestors and highly diverse multicellular forms happened too abruptly to have been accomplished by familiar incremental mechanisms, uniformitarianism does not seem to be a satisfactory framework for the earlier phase of animal evolution.

Newman may be wrong about some things but he is not boring.

This entry was posted on Sunday, October 12th, 2008 at 11:48 pm and is filed under Evolution, Front-loading. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.