Michael Denton’s Evolution: Still a Theory in Crisis presents case after case of “baroque” patterns in nature that defy evolution (see the short film Biology of the Baroque for examples). Inspired by D’Arcy Thompson’s century-old classic, On Growth and Form (1917, second edition 1942), Denton argues for a view of biology very different from Darwinism’s random walk.
Structuralism, as presented by Thompson and by Denton, is the view that
a significant fraction of the order of life and of every organism is the result of basic internal constraints or causal factors that arise out of the fundamental physical properties of biological systems and biomatter. In other words, biological order that does not result from adaptation to satisfy functional ends. (Denton, p. 14).
This was also the view of Richard Owen in Darwin’s day. The Darwinians took the opposite view, called functionalism, that organisms adapt to changing environments — without aim or plan. The structuralists invoke universal forms or pre-ordained capacities that direct the development of organisms with physical forces, as seen in the self-organizing cell membranes and the conformation of plants and animals to mathematical ideals such as the Golden Ratio.
From Sphere to Elongated Animal
A remarkable case of patterning that appears to fit the structuralist view was announced by scientists at U.C. Santa Barbara. Otgar Campàs at the university was looking into the question of how a spherical zebrafish embryo becomes elongated into the adult form, “engineering organs” in the process.
Using state-of-the-art techniques he developed, UC Santa Barbara researcher Otger Campàs and his group have cracked this longstanding mystery, revealing the astonishing inner workings of how embryos are physically constructed. Not only does it bring a century-old hypothesis into the modern age, the study and its techniques provide the researchers a foundation to study other questions key to human health, such as how cancers form and spread or how to engineer organs.
The “century-old hypothesis” is Thompson’s book On Growth and Form. In that book, Thompson had suggested that embryonic shape development is somewhat like glassblowing, in which a physical force is applied to a liquid to direct it into a shape that becomes solid. The transition from liquid to solid is a well-known process in materials science called “jamming.” Examples include directed forces applied to foams and emulsions to turn them into solid shapes using molds. Campàs found the metaphor instructive, and so the news item announces, “Careful — You Are Made of Glass.”
But how are we like glass, being made up of cells? Campàs and his team, publishing in Nature, describe how they found a way to measure the physical forces of attraction between cells in a zebrafish embryo. The embryo starts out in a spherical shape, but within 30 minutes takes on its familiar elongated fish shape. The team found that cells in the tail region, which becomes stretched out during the elongation process, begin in a “liquid” state, with more space between the cells and more jiggling. Gradually, they become more compacted, “jamming” into a solid when they turn into somites, the tissue cells comprising the final shape.
Cells coordinate by exchanging biochemical signals, but they also hold to and push on each other to build the body structures we need to live, such as the eyes, lungs and heart. And, as it turns out, sculpting the embryo is not far from glass molding or 3D printing. In their new work,”A fluid-to-solid jamming transition underlies vertebrate body axis elongation,” published in the journal Nature, Campàs and colleagues reveal that cell collectives switch from fluid to solid states in a controlled manner to build the vertebrate embryo, in a way similar to how we mold glass into vases or 3D print our favorite items. Or, if you like, we 3D print ourselves, from the inside.
Lenne and Trivedi, commenting on the paper in Nature, find the comparison fascinating. “Tissue ‘melting’ sculpts embryo,” their headline announces.
Collections of cells in the tails of zebrafish embryos have now been found to transition between behaving as solids and fluids. This transition is responsible for the head-to-tail elongation of the embryo.
Lest we carry the analogy too far, cells have resources not available to lifeless materials. The cell-adhesion protein N-cadherin controls the cell spacing and the amount of “jiggling” the cells exhibit during the transition. The “jamming” transition from fluid-like state to solid state, in other words, is carefully orchestrated by complex molecular machines. N-cadherin is a big protein, with 906 amino acids! It acts like a “zipper” between cells. So just as fluid glass will not blow into a vase without a designing guidance, an embryo will not grow from sphere to elongated shape without pre-programmed guidance provided by the genetic and epigenetic codes.
UCSB’s discovery, fascinating as it is, represents just a tiny part of the wonder of embryo development. Basically, they found that fluid-to-solid “jamming” takes part in some stages. But now look at the stunning images of fish and other animals produced by the University of Kansas. By removing muscle tissue with enzymes and staining the remnants in special ways and then mounting them in gelatin, they revealed the intricacies of animal forms in “otherwise impossible images.”
That zebrafish embryo studied at UCSB doesn’t stop with an elongated shape. Within the embryo, all kinds of organs and tissues become organized and positioned on a predetermined developmental timetable. Readers may remember the animation of an egg becoming a chick in Illustra Media’s film Flight (watch the clip here). In just 21 days, a seemingly miraculous transformation has occurred. It’s not a glass-shaped chick form, but the real bird!
The Typological View
Denton’s 1985 book Evolution: A Theory in Crisis influenced many in the intelligent design community with his evocative descriptions of the complexity of life, from the single cell to animals and plants, showing how these things defied Darwinian evolution. In the book’s successor, Evolution: Still a Theory in Crisis, he elaborated on the “typological” view of organisms that he introduced in the earlier classic. He offered the structuralist views of D’Arcy Thompson convincingly, showing that the particulars in the living world not only defy Darwinian evolution, but exhibit “a universe of non-adaptive forms.” After discussing the intricate patterns in diatoms and radiolarian shells, for instance, he pointed to plants for more examples:
It is not only the unicellular that abounds with what appear to be abstract formal patterns. Even on the most cursory and passing observation of some of the most familiar natural forms, such as the forms of leaves and the variety of phyllotactic arrangements that might be observed in any suburban garden, it is hard to resist concluding that a vast amount of botanical order serves no specific adaptive end. Take the number of petals on different species of flower. In many species the number of petals often corresponds to a Fibonacci number, e.g., bloodroot, eight; blackeyed daisy, thirteen; shasta daisy, twenty-one; and field daisy, thirty-four. Would anyone seriously insist that the number of petals in each species is adaptive? (p. 77)
By the end of the book, having demolished Darwinism and other “functionalist” views of living forms, he presents the ideas of Thompson, Richard Owen, and other structuralists as clear winners. In his other books and films, Denton awes readers and viewers with incredible coincidences between life and the properties of the sun and earth, with its atmosphere, water and minerals (see The Wonder of Water). Even the form of the human body, he explains, closely comports with the physical necessities of life on a planet with the right atmosphere and sun (watch Privileged Species).
Structuralism doesn’t claim to answer all questions, and there are other perspectives bearing on intelligent design. But this is a very potent one.
Photo: A scene from The Biology of the Baroque, via Discovery Institute.