[geodesic 01136] Albert K. Harris quote on biological modeling

Phil Earnhardt phil at floatingbones.com
Wed Sep 28 10:27:23 PDT 2011


Albert K. Harris is an embryologist at UNC Chapel Hill (
http://www.bio.unc.edu/faculty/harris/ ). In his 1997 Scientific American
article, cellular tensegrity researcher Donald Ingber references Harris's 1980
paper "Silicone Rubber Substrata: A New Wrinkle in the Study of Cell
Locomotion". Harris's paper is available for download at
http://faculty.washington.edu/nsniadec/ME599/S09/private/19Harris.pdf;
Ingber's SciAm aritcle is available at
http://www.childrenshospital.org/research/ingber/PDF/1998/SciAmer-Ingber.pdf I
don't believe that Harris has ever published anything about cellular
tensegrity, but his work helps provide the foundation (or maybe the substrate)
for that research.

Harris wrote the paper, "Cytokinesis: The mechanism of formation of the
contractile ring in cytokinesis." It was published in the 1994 text
"Biomechanics of Active Movements and Division of Cells" (ISBN
0387579516). Harris writes with a wonderful plain-speaking style on this
fairly esoteric topic. He ends his essay with some delightful commentary about
modeling:

“Systems of interacting forces and stimuli do not have to be very complicated
before the unaided human intuition can no longer predict accurately what the
net result should be. At this point computer simulations, or other
mathematical models, become necessary. Without the aid of mechanicians, and
other skilled in simulation and modeling, developmental biology will remain a
prisoner of our inadequate and conflicting physical intuitions and metaphors.”

Harris has stared down and captured a fundamental limitation of our thinking
about cellular structure. His paper notes that subtle mechanical forces in the
cell tend to play a dominant role in its structural behavior, something that
will almost certainly be missed by traditional approaches. I do not know how
the embryonics researchers have responded to his 1994 challenge.

The best example of the kind of revolution through new modeling was the work
of Gerald Sussman and Jack Wisdom of MIT. In the mid-1980s, they created the
Digital Orrery. They used this device to precisely predict the movement of
objects in the solar system over millions of years. In my opinion, their 1988
paper "Numerical Evidence that the Motion of Pluto is Chaotic" was the last
nail in the coffin of Newton's clockwork universe. No orrery -- or other
clockwork device -- could ever be used to model chaotic behavior; a new kind
of model was mandatory.

I believe Harris's idea is equally applicable to our musculoskeletal
network. Anatomy texts that enumerate the three classes of levers invariably
ignore that the geometry of our joints is neither rigid nor fixed. Subtle
shifts in the spaces between our bones can have a dramatic influence on the
structure's ability to hold our bodies, move our bodies, and do work. Until we
explore models that embrace those and other subtle shifts, we will dwell in a world of
inadequate explanations of our bodies. I've commented on the listserv of the
need for models and visualizations for understanding tensegrity
structures. Harris eloquently pleads the case to pay attention to the model.

I found the Harris quote through a paper published by Konstantin Volokh of
Technion – Israel Institute of Technology, "On Tensegrity in Cell
Mechanics". The author has a download link to the article's PDF and welcomes
discussion at http://imechanica.org/node/11072 .

--phil




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