Bucking the Zeitgeist

What happens when biologists and a physicist try to create a grand unifying theory of biology?


Richard Gallagher
Despite 728 citations, the article polarizes opinion to this day.

Today's biology is a frenzy of convergence. Driven by huge datasets and the tools to analyze them, comparative genomics and systems biology are being used to define the common basis of life and the dazzling variations on its central theme. Given the spirit of the times, any attempt to advance a grand unifying theory of biology would get a reasonable hearing today.

Rewind 10 years to 1997, however, and the zeitgeist of biology was quite different. Reductionism was king. Excellence in molecular biology was a major driver, and research was more noticeably compartmentalized, with the focus on providing a full description of the discrete pieces of the puzzle of life. For example, Science magazine's "Breakthrough of the Year" in the mid-90s featured p53, DNA repair and cloning. How would a theory that dared to span the breadth of biology be received in such a reductive setting?

That question was tested by the submission of a paper to Science called "A General Model for the Origin of Allometric Scaling Laws in Biology." 1 Two biologists - Jim Brown and Brian Enquist - and a physicist, Geoffrey West, shared a common interest in why rates and times scale as a fourth powers of body mass, and had developed a metabolic theory that they said could predict fundamental characteristics of vertebrate cardiovascular and respiratory systems, plant vascular systems and insect tracheal tubes.

I'm in a good position to tell you how that theory was received: I was the editor at Science who handled the original research paper, a process that is etched vividly upon my memory. Bucking the zeitgeist is never easy, and the divisions riven by the work were immediately evident.

The two members of the Board of Reviewing Editors had diametrically opposite reactions, and we decided to send the paper out for formal peer review. The first two reports were enthusiastic: "A real breakthrough" and an "original theoretical approach. But the third, an expert in fluid flow who took longer to identify was unimpressed, finding the work "fundamentally flawed."

This negative reviewer declined to consider a revised manuscript, so two further expert views were sought. They raised some further grumbles, but these were not fundamental. As the editorial team, we felt justified in proceeding to publication with one ecstatic, two enthusiastic, two lukewarm and two implacably negative reviews.

Despite 728 citations, the article polarizes opinion to this day. The work of its authors is profiled here. Over the course of the decade their theory has extended tentacles across the entire spectrum of biological (and potentially biomedical) phenomena, including energy and resource use, genome length, and life span. A recent Nature article described the work as "breathtaking in its ambition and scope." 2 West recently widened the ambition and scope still further-to social organizations-with a brief essay in Harvard Business Review reporting that "cities manifest power-law scaling similar to the economy-of-scale relationships observed in biology: a doubling of population requires less than a doubling of certain resources. The material infrastructure that is analogous to biological transport networks-gas stations, lengths of electrical cable, miles of road surface-consistently exhibits sublinear scaling with population." 3

It would appear that August Everding, the German opera director, was wrong when he said, "Whoever marries the zeitgeist will be a widower soon" - at least when it comes to biology.


1. G.B. West, J.H. Brown, B.J. Enquist, "A general model for the origin of allometric scaling laws in biology," Science, 276:122-6, 1997. | [PubMed]
2. D. Robinson, "Biology's big idea," Nature, 444:272, 2006.
3. G.B. West, "Innovation and growth: Size matters," Harvard Bus Rev, Feb 2007.


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Bucking the Zeitgeist
by John Torday

[Comment posted 2007-03-12 20:07:41]
The central idea in West et al's 1997 Science paper is that biologic systems are scalar due to metabolic principles. But that unfortunately only describes the process, but doesn't provide the underlying mechanism of evolutionary biology. The core issue is 'why' do cells cooperate metabolically, and how does that principle explain evolution. We have previously published several position papers that demonstrate how cell physiology, when looked at as the basis for development, homeostasis, aging and repair, can be seen as a continuum of cell/molecular signaling pathways that integrate cell metabolism and lung function (Torday JS. A Periodic Table for Biology. The Scientist, The Scientist 2004 Jun 18(12): 32-33.;Torday JS, Rehan VK. Deconvoluting lung evolution using functional/comparative genomics. Am J Respir Cell Mol Biol. 2004 Jul;31(1):8-12;Torday JS, Rehan VK. The evolutionary continuum from lung development to homeostasis and repair.Am J Physiol Lung Cell Mol Physiol. 2007 Mar;292(3):L608-11). It is only through such an integrated approach that we will be able to integrate genomics into phenotypes of health and disease.



Bucking the Zeitgeist
by Gregory C. O'Kelly

[Comment posted 2007-03-06 00:50:14]
The metabolic theory of everything being pushed by West et al. does not in fact buck any sort of zeitgeist, and the blizzard of criticisms assailing it, few of which are valid, result from the incompleteness of the theory. In short, the theory is hobbled by a failure to escape the zeitgeist or, for want of a better term, the epistemological ossification of the life sciences. Here we have a team of ecologists and a physicist who assert that thermogenesis is part of metabolism when examination of Kleiber's Law reveals there is not a single term in it that deals with the kinetic theory of heat. Nor is there a term in it that might be applicable to fluid or hemodynamics. Yet West et al. remain convinced that capillary terminal size can account for motor activity, a view that Kozlowski and Konarewski point out as a major flaw.

In turn West et al. aver that the study of metabolism based upon respiratory considerations is adequate to account for the metabolism of cells and elephants. Nothing is said about food sources. West smugly claims that the equation relates metabolic rate to body mass and metabolic efficiency, yet the term for metabolic efficiency is completely lacking in their published treatments - as if the term's value was unquestionably 100% because metabolism includes (for West, Gilooly, etc.) not just anabolic reduction reactions, but also heat generation.

And then we have the common and widely accepted account of Kleiber's Law that shows a straight line relating metabolic rate to body mass. Have these guys ever graphed the real equation? It's not at all straight, and varies drastically from things less than one gram to things over one gram. The only straight line is at one gram.

So, until West et al. go back to the drawing board and consider the numbers for a wide range of body masses and values for metabolic efficiency (which does not include thermogenesis), and until these guys consider the role of food in metabolism rather than just the blood-borne delivery of oxygen, they will continue to be sniped at by critics like Speakman and Kozlowski who raise objections that are easily parried otherwise.

Appeals to fractals to account for extra-dimensional efficiency in nutrient delivery is deplorable. The extra-dimensionality is the result of consideration of RATES, and so the extra dimension is one of time, not space. Fractals do not add another ineffable dimension to Euclidean geometry. Kleiber's Law is an excellent equation, and more revealing of the evolution of life, from archaebacteria to human societies, then it will ever receive at the hands of West et al. as long as they remain dedicated to a life sciences that celebrates a Central Dogma of Biology and that reveres the awards of pompous old men in Stockholm for things like the ionic channel model of nerve impulse propagation or the proticity of Peter Mitchell. In 1993 John Eccles recanted the model he, along with Hodgkins and Huxley, received a Nobel in 1963. Eccles said the model could not account for information processing and encoding by the nervous system. The ionic channel model is still taught today as a fundamental of physiology and neuroscience. Until West et al. overturn the 1902 account from Julius Bernstein of the nature of bioelectricity and its connection to the thermodynamics of Walther Nernst's 1888 equation, they are still impeded by a vitalist zeitgeist of life science teaching that genetics is more important than metabolism.






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