Category Archives: books

On Purpose

“When Henry Fawcett commented to Charles Darwin that some scientists found Darwin too theoretical and believed that he should just let the facts speak for themselves, Darwin responded: ‘How odd it is that anyone should not see that all observation must be for or against some view if it is to be of any service.’3

This quote is taken from a review in Science magazine of cognitive neuroscientist Paul Thagard’s book: The Brain and the Meaning of Life1,2. I found the review intriguing, particularly the section which comment’s on Thagard’s attempts to use a scientific point of view to answer the question: “What kind of government should countries have?”

However, I reproduced the quote, above, because it struck a chord in my mind. To my mind, Darwin’s viewpoint discards the great utility and pleasure that one may find in observation for the sake of observation. That is, scientific exploration. It is not always possible to observe, to collect information with a hypothesis in mind, and such exploratory behavior can inspire hypotheses or new avenues of scientific discovery. How limiting to always approach a situation with a theory, a reason, a preconception.

In fact, I don’t believe that Darwin was suggesting anything so strong as to eliminate exploration from one’s methods, his own travels as a young man were likely not begun with a plan of attack to corroborate his grandfather Erasmus’ evolutionary theory, though this was the end result. However, science in the present day is extraordinary goal oriented; every scientist must compete for funding and the drive to present completed work is thus ever present. There is something romantic and collaborative in the idea that some men of science in Darwin’s age wanted the facts to “speak for themselves.”

Collaboration is something that we can always use more of.

1. Shermer, M (2010) Meaning-Making Neurons. Science, 328: 693-694; DOI: 10.1126/science.1189752
2. Thagard, Paul. The Brain and the Meaning of Life. Priceton: Princeton University Press.
3. Letter, C. R. Darwin to H. Fawcett, 18 September 1861;

On Corn & Carbon

In the fascinating, free 1st chapter of Michael Pollan’s new book The Omnivore’s Dilemma, he makes the point that American industrial agriculture is largely based on corn. Most of our livestock species are fed on corn, and a laundry list of comestibles contain additives derived from it. He goes on to explain that it is possible to quantify how much corn one consumes directly or indirectly due to the type of photosynthesis that corn engages in.

All forms of photosynthesis involve the fixation (harvesting) of carbon which is made into simple sugars subsequently consumed for energy. Photosynthetic types can be categorized, according to the specifics of the carbon fixation process, as C3, C4, or CAM. Corn is a C4 grass. This means that it has developed an adaptation to deal with dry, arrid climes. Specifically, the fixation of carbon is achieved first by PEP carboxylase, which basically buffers it. Plants absorb carbon in the form of CO2 through holes on their leaves called stomata. However, water can also be lost through these pores, so they must be closed to prevent dehyrdation. During these periods, the lack of available CO2 can become a problem because the costly reverse reaction of photosynthesis: photorespiration, occurs. Not so for corn and it’s C4 cronies; their buffer of carbon prevents wasteful photorespiring. In addition to this benefit, it turns out that there is another significant consequence of such a strategy: indiscriminate absoprtion of carbon isotopes.

Most (98.9%)of carbon is C-12, it has 6 protons and 6 neutrons. Almost the entirety of the remaining 1.1% is C-13, 6 protons and 7 neutrons, a mass difference of 1.6749 × 10^−27 kg. Most plants preferentially absorb C-12, but not C4 plants. Given such a minute difference between these atoms, it is quite amazing that plants have any ability to discriminate between them. It turns out that differences in the rate of (1) diffusion into the stomata, (2) absorption of C02 by water in the plant, and (3) diffusion of carbon out of the plant is what makes the difference1. Beyond these passive properties, PEP carboxylase has somehow managed to develop a bias in which type of CO2 (preferring C-13) it fixes. It is damned astounding that an enzyme can have such specificity, discriminating such a small mass difference (there is no charge & so probably not much of an electron-shell-structure difference). The end result of all this is that the ratio between the two isotopes in, for example, your flesh is informative about what type of plant supplies most of your carbon.

It is unclear if monitoring this value will ever be relevant to the individual. The potentially deleterious effects of eating large amounts of corn on health and well being are up for debate. It is immediately interesting, however, from a socio-cultural standpoint. Mr. Pollan makes this point quite well in an article he wrote for The New York Times2. He points out that the consequences of industrial monoculture farming are probably not sustainable in the long term. I firmly believe that questioning the long term feasibility of our life styles is important for continued human survival and happiness. The ability to measure corn consumption on a large scale will allow us to monitor and understand this potential problem in a very direct way.


1. Farquhar, G.D., Ehleringer, J.R., & Hubick, K.T. (1989) Carbon Isotope Discrimination and Photosynthesis, Annual Revews of Plant Physiology and Plant Molecular Biology, Vol. 40 pp. 503-537
2. Pollan, M. (2007) Unhappy Meals, The New York Times (