Chapter 4: When Cooking Began

First Ingredient, Solid Case Studies

                Wrangham begins this chapter by acknowledging the great discrepancy over the approximate date for the beginning of cooking in human evolution. The fact seems so obvious I’d like to gloss over this a bit a fast forward to the part of the chapter that interested me the most. Wrangham states that by searching the fossil record for morphological changes (many of which are chronicled and explained in previous blogs) we can put our finger on when cooking began by the adaptions it caused. He uses the parallel argument that because many animals respond to dietary changes with inheritable adaptions, humans could have to. I would agree with this, except I think he uses a poor example:

“Studies of Galapagos finches by Peter and Rosemary Grant showed that during a year when finches experienced an intense food shortage caused by an extended drought, the birds that were best able to eat large and hard seeds—those birds with the largest beaks— survived best. The selection pressure against small-beaked birds was so intense that only 15 percent of birds survived and the species as a whole developed measurably larger beaks within a year. Correlations in break size between parents and offspring showed that the changes were inherited (Wrangham, 2009).

Now, I don’t think this is a proper example—it appears a bit too “apples to oranges.” Here’s why: in the case for cooking causes evolutionary adaptions Wrangham agrees that the nutritional benefits of food changes the bodies of hominids in an inheritable way. Here it is not the nutritional value (or a food processing method that increased the nutritional value) of food that is being evaluated, but the scarcity of the resource. This would make sense as an analogy to the theory that Robust Australopithecines (with extremely strong chewing apparatuses) may have gone extinct because they were too specialized and could not adapt when food availability favored a more gracile set of chompers. To present a strong argument for his point, I think Wrangham needs to find an example that says perhaps “birds eating nuts with impressive protein levels showed increased wingspan and muscle development.” Now that is made up, but I set out to find some examples of studies that I believed better support what Wrangham was trying to prove through this analogy.

To be honest, the related research I could find was limited. I read a case study detailing how mice exposed to a high-fat diet experience heritable changes in their gut microbial and metabolic phenotypes, but not a study that spoke of the link between diet changes and drastic phenotypic change in other animals (Serino M, et al., 2011). I feel like this argument is crucial to Wrangham’s book, and he could have spent more time on his supportive examples here.

References:

Serino M et al. 2011. Metabolic adaption to a high-fat diet is associated with a change in the gut micribiota.  Available online at http://gut.bmj.com/content/early/2011/11/22/gutjnl-2011-301012.full.pdf.

Wrangham R. 2009. Catching fire: how cooking made us human. New York: Basics Books.