Epilogue: The Well-Informed Cook

My Epilogue: The Well-Informed Reader


One final project later, I can say that I have enjoyed reading Richard Wrangham's "Catching Fire: How Cooking Made us Human." Overall, I have my praises and my critiques.  Let's start with the later.


1. Wrangham frequently bring us major changes (in his own words: smaller guts, bigger brains, bigger bodies, and reduced hair; more running; more hunting; longer lives; calmer temperaments and a new emphasis on bonding between females and males) and justifies them through his "cooking-causes-all" perspective. Although his arguments are (mostly) well-supported and obviously thought-provoking, he only briefly acknowledges other opposing theories. Although this was a boon for me, as I could then could then explore these alternatives in my blogs (see posts such as The Trade Off: Little Jaws, Big Brains? and The Roots of Romance… or Pair Bonding at Least) Wrangham could better support his own arguments by effectively exploring and debunking others.


2. Case study gaps. for example, he notes the 99.3% of societies that have male hunting only. But what about the.7% of societies that do feature women hunters? Understanding the outlier is important too. In this instance and others, I believe Wrangham over generalizes information that inherently has exceptions and gray-areas. 


3. My biggest critique: Wrangham's attitude. I feel, as a reader, that in not considering the gray areas and alternate hypotheses, he presents his hypothesis as an academic panacea for the advent of humanity as we morphologically and socially know it. I believe he does not leave enough room for other ideas, and it is not realistic to assume that cooking and cooking alone caused changes that were influenced by a number of (or even completely different) factors. Therefore, I do not recommend a reader pruruse this book without investigating the wellspring of other hypothesis and literature out there. But I do recommend it.


Why?


Because through his use of diverse examples, past and present information on the human diet (he brings us all from Australopiths all the way up to the works of renown foodie Micheal Pollen) and his accessible, non-technical prose, Wrangham has written a good, thought-provoking book. "Catching Fire" entertains and educates the intellect (a rare combination) on a topic that we can all relate to. In summary, I say bon appetite to this evolutionary literature entree, but take it with a grain of salt.

Chapter 8: The Cook’s Journey

The Gene’s Journey

In this final chapter, Wrangham summarizes the points in human evolutionary history that were influenced by the use of fire and the nutritional benefits of cooked food. Because I have already touched on many of these morphological and social changes, I wanted to zero in on a concept Wrangham mentions briefly in chapter eight: the “Thrifty Gene Hypothesis.” I had never heard of it before doing this extra research, so I figured it deserved further explanation.

The “Thrifty Gene Hypothesis” “…claims that because the environments of our hunter-gatherer ancestors were highly seasonal, we are physiologically adapted to periods of feast and famine. Accordingly, ancestral humans supposedly digested and stored energy in their bodies with exceptional efficiency” (Wrangham, 2009).  This idea was first purposed in 1962 by American population geneticist James Neel (McDermott, 1998). Neel (1962) sought to explain the apparent genetic predisposition for diabetes. In his research, he concluded that obese people with diabetes had genes that caused them to intake more food, and store these calories better.  Neal (1962) stated that people with this genotype had suppressed blood sugar levels that caused them to be hungry more frequently and to eat more as a result. He believed that this was an ancestral adaption, as Wrangham stated, for famine survival.

Wrangham states that this theory is no longer accepted, and that obesity is rather viewed as “a result of eating exceptionally high-energy, calorie dense foods, rather than from ancient adaptation to seasonality” (Wrangham, 2009). However, he doesn’t explain WHY the thrifty gene idea was tossed away.

Speakman (2008) states simply that the thrifty gene never had enough time to evolve. This genotype would have had only approximately 12,000 years to spread into 30% of our population (the percent which suffers from obesity).  Famines do not exert a high selective pressure, with a mortality rate of only 5-12% (Speakman, 2008).  Beginning with modern hominid ancestors in Africa around 2 million years ago, this gene would have had to be passed down successfully through the famine survivors for about 100,000-70,000 generations (Speakman, 2008). Especially considering that the same source states most deaths in famine are actually caused by cholera, typhoid, diarrhea and other illness, anti-starvation genes simply haven’t had enough time to become so dominant.

References:

McDermott R. 1998. Ethics, epidemiology and the thrifty gene: biological determinism as a health hazard. Social Science & Medicine. 47:1189-1195.

Neel J. 1962.  Diabetes Mellitus: A “Thrifty” Genotype Rendered Detrimental by “Progress”? Am J Hum Genet . 14:353-362

Speakman J.R. 2008. Thrifty genes for obesity, an attractive but flawed idea, and an alternative perspective: the ‘drifty gene’ hypothesis. International Journal of Obesity. 32:1611-1617.

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

Chapter 7: The Married Cook

The Roots of Romance… or Pair Bonding at Least.

Pair-bonding can be explained by a number of hypotheses. Wrangham states that the heart of the matter may have started at the hearth of the home. It is also acknowledged that pair-bonding wasn’t so much “love at first sight” as an economy of services.

“Whether or not the women wanted to, they cooked for their husbands. As a result, married men were guaranteed adequate food whether they returned late, tired and hungry from a day’s hunting or came home relaxed and early from discussing politics with a neighbor" (Wrangham 2009).

           

The man benefits from the “woman-the-cook” arrangement because he is guaranteed a supply of food, regardless of his own provisioning success rate. The woman, in exchange, only has to share her food with one male, who protects her from the others males within their social group who might pilfer her food otherwise. A trade-off of sorts.

Let’s continue, because further quotes from this chapter illustrate how our societal concept of marriage many have originated from this marriage of convenience.

“Many such examples suggest that the mating system is constrained by the way species are socially adapted to their food supply. The feeding system is not adapted to the mating system” (Wrangham, 2009).

So the food provisioning abilities of females may have proved more attractive, than well, sexual attraction. Wrangham (2009) goes on to say how a women is a valuable commodity not as much for her reproductive capabilities as much as her cooking abilities. This mutual household economy (protection traded for food) may have evolved into long lasting, evening loving relationships. Pair bonding.

It’s an interesting thought to think the origins of our societal concepts of romance begin with man’s empty stomach. But as always, Wrangham only presents one hypothesis for a very complex issue.

Pair bonding is old and not unique to humans. Laden (1999) states that in mammal species with low levels of sexual dimorphism, pair bonding is common. For us, pair bonding became standard about 1.9 million years ago— an important change in mating strategy (Laden, 1999). Pair bonding (to clarify) is the “long-term affiliation, including a sexual relationship, between two individuals” (Quinlan, 2008). Though mutual, they are not quite even. According to the same source, pair bonds are most stable when men do the majority of the subsistence work, because women and children are so vulnerable and dependent.

Why are women so in need of male protection?

Enter the Child-Rearing Hypothesis for Pair Bonding. With our extended ontogeny, and physically vulnerable infant forms, Homo sapiens are especially dependent upon a high paternal investment. This can come in the forms of food provisioning, education, protection and socialization. Marlowe (2002) states that among the Hadza, pair bonding appears most critical for the mother while she is still lactating, and her offspring is completely dependent upon her. During this time, fathers can contribute in two ways. (1) they can directly care for the child, or more often they (2) care for the mother, protecting her and supplementing her food supply so that she can care for the infant (Quinlan, 2008). Here emerges another trade off that results in increased reproductive success for both male and female. Here emerges pair bonding.

So although cooking may have helped tie together males and females, there are other explanations for why we tie the knot.

References:

Laden G. 1999. Light my fire: cooking as key to modern human evolution. Science Daily. Available at: http://www.sciencedaily.com­ /releases/1999/08/990810064914.htm

Marlowe F. 2002. A critical period for provisioning by Hadza men: implications for pair bonding.  Human Evolution and Behavior. 24: 217-239.

Quinlan R. 2008. Human pair-bonds: evolutionary functions, ecological variation and adaptive development. Evolutionary Anthropology. 17:227-238.

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

Trinkaus E, Churchill SE, and Ruff CB. 1994. Postcranial robusticity in Homo. II: humeral bilateral asymmetry and bone plasticity. Am J Phys Anthropol 93:1–34.

Chapter 6: How Cooking Frees Men

 ...and women! (in some contexts)

        

            In this chapter, Wrangham discuss the division of food-related labor between men and women. While women tend to look for predictably available resources, men pursue foods that are riskier to get and much harder to find (Wrangham, 2009). Hence hunter-gatherer men hunting large, potentially dangerous ungulates. As Wrangham discussed tribe after tribe that had social structures based off this principle, I began to wonder which groups of people, if any, had women hunters. Wrangham (2009) states that 99.3% of hunting in known societies is male, so the odds aren’t good. Still, I wanted to explore who the women of that .7% might be.  

            According to Noss and Hewlett (2001) “It is obvious that woman can hunt, but they do not do so in all contexts.” In an interview with the Guardian, Hewlett states that in the Aka tribe of Central Africa, the women hunt while the men spend 47% of their time with their infants—more than fathers in any other cultural group in the world (Moore, 2005).  Men of this forest dwelling hunter-gatherer tribe impose little ideological/political control over women, and this leniency has allowed women to become knowledgeable and experienced hunters (Noss and Hewlett, 2001). Women and men frequently trade domestic roles, one minding the children while the other hunts, gathers, or maintains the camp (Moore, 2005). In the same interview Hewlett states:

            "But, and this is crucial, there's a level of flexibility that's virtually unknown in our   society. Aka fathers will slip into roles usually occupied by mothers without a second thought and without, more importantly, any loss of status - there's no stigma involved in the different jobs."

            Among the Aka, women are as good, if not better than men as net-hunters (Noss and Hewlett, 2001; Moore, 2005). And Aka women are not alone. The women of the Agta tribe of the Philippines hunt wild pig and deer with considered efficiency using spears and bow-and-arrows (Estioko-Griffin and Griffin 1975, 1981).  Other women hunters included the Woods Cree who hunt moose and caribou, whether they are married or not, the Matses in the Peruvians Amazon who hunt alongside their husbands, and many more. (Brightman 1996; Romanoff 1983 respectively).

            However among these tribes, a pattern emerges. Remember how Wrangham suggested that women select for more readily-available resources that are reliable and of minimal risk? The Hawkes et. al (1997) hypothesis states that women who are “the day-to-day providers for their families” and “regularly hunt” more often than not “hunt for small and medium-sized game that is regularly acquired and shared within the family rather than for larger game that is irregularly acquired and shared with the entire community.” (Hawkes et. Al, 1997; Noss and Hewlett, 2001). According to Noss and Hewlett (2001) this is evident for example in the previously mentioned Agta women, who hunt far less often, and for small animals. I find this interesting that, considering Wrangham’s assertion, women tend to hunt in the same way they gather.  Yet that .7%, in my opinion, is a brave bunch. Wrangham could have given them at least one blog post’s worth of a mention.

References:

Brightman R. 1996. The Sexual Division of Foraging Labor: biology, Taboo, and Gender                                               Politics. Comparative Studies in Society and History. 38:687-729.

Estioko-Griffin A, and Griffin P. 1981. Woman the Hunter: The Agta. In Woman the Gatherer. Frances Dahlberg, ed. New Haven: Yale University Press. 121-151.

Estioko-Griffin A, and Griffin P. 1975. The Ebuked Agta of the northeasterm Luzon.Philippine  Quarterly of Cultural and Society. 3:237-244.

Hawkes J, O’Connel J, and Blurton Jones N. 1997. Hadza Women’s Time Allocation, Offspring Provisioning and the Evolution of Long Postmenopausal Life Spans.  Current Anthropology. 38:551-577

Moore J. 2005. Are the men of the African Aka tribe the best fathers in the world? The Guardian.  Available at: http://www.guardian.co.uk/society/2005/jun/15/childrensservices.familyandrelationships

Noss A, and Hewlett B. 2001. The Contexts of Female Hunting in Central Africa. American                                          Anthropology. 103:1020-1040. 

Romanoff A. 1983. Women as hunters among the Masters of the Peruvian amazon.                                                       Human Ecology.  11:338-343. 

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

Chapter 5: Brain Foods

Having Your Cake and Efficiently Digesting It Too.

In Chapter Five, Wrangham discusses how our genus Homo experienced an evolutionary trade off, giving up big guts in order to grow big brains. Diverting more of our Basal Metabolic Rate (BMR) toward fueling our calorie-hungry brains, we had to compromise by shrinking the size of calorie-consuming stomach. Brains and stomachs, along with hearts, kidneys and livers, are the most expensive organs in the human body in terms of consumption of metabolic energy (Wrangham).  Aiello and Wheeler (1995), summarize this nicely in the following chart, which was reprinted (Billings, 1999):

Furthermore, the same source states:

“Since gut size is associated with dietary quality (DQ), and the gut must shrink to support encephalization, this suggests that a high-quality diet is required for encephalization. That is, a higher-quality diet (more easily digested, and liberating more energy/nutrients per unit of digestive energy expended) allows a smaller gut, which frees energy for encephalization.”

But was shrinking the size of the gastrointestinal track the only adaption that could have facilitated encephalization? I wanted to conduct a bit more research into morphological or behavioral options that could have allowed us to grow bigger brains, and to evaluate their validity.

Option 1. The Other Big Spenders

As previously mentioned, the heart, kidneys and liver also consume a large proportion of our energy. However shrinking any of these organs could have much greater consequences. The brain depends on glucose processed by the liver, so it has to be of a large enough size to function properly. This is especially important considering the brain has no glucose stores of its own and depends on that which flow through the blood stream (Aiello and Wheeler, 1995). The brain, if it was to increase in volume, would need even more glucose, so it is best not to shrink the liver. Aiello and Wheeler (1995) also state that shrinking the heart may compromise circulation which brings a constant flow of oxygen and nutrients to the brain, another unviable option. Finally, the kidneys have high metabolic rates as well, but compromising their function of removing waste products from the blood stream and processing urine would be especially dangerous in the habitats where water is limited, which is likely the case with Africa hominids (Aiello and Wheeler, 1995).

Option 2. Cheaper Cuts

Perhaps a reduction in skeletal muscle could balance out the energy budget? Not quite, because muscle tissue has a much lower BMR, so to offset the brain’s high BMR, much more muscle tissue would have to be eliminated, at least 70% (Aiello and Wheeler, 1995).  

Option 3: Have Your Cake and Eat it Too

Consume more calories, keep both. Sounds perfect, right? Aiello and Wells (2002) states increased BMR imply that an organism must either increase the quality or quantity of food. Increasing the quantity is unlikely, states the same source, because Homo ergaster needed adequate time for traveling, socializing and resting, not just for feeding. The same source purposes a drastic increase in diet quality, adding more soft bulbs and tubers and increasing meat consumption. And not surprisingly, the increased nutritional content of cooked food would help too—this leads back to support Wrangham’s original hypothesis. Therefore, it appears after a brief comparison that the shrinking of the GI track may be the most energy efficient way to balance out encephalization. 


Also: Wrangham brings up the curious case of the walking science experiment Mr. St. Martin, whose open-air stomach led to the discovery of the digestive process. Learn more at: radiolab.org

Resources:

Aiello L, and Wheeler P. 1995. “The Expensive-Tissue Hypothesis: The Brain and the Digestive System in Human and Primate Evolution.” Current Anthropology. 36:199-221

Aiello L, and J.C.K. Wells. 2002. “Energetics and the Evolution of the Genus Homo.”  Annual Review of Anthropology. 31:323-338.

Billings T. 1999. “Comparative Anatomy and Physiology Brought Up to Date: The Relationship of Dietary Quality and Gut Efficiency to Brain Size.” Available at www.beyondveg.com

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

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.

Chapter 3: The Energy Theory of Cooking

Chapter 3: The Energy Theory of Cooking

Enter Junk Food

            In this chapter, Wrangham presents arguments based on nutritional science how cooking facilitates food digestion (I think he may be getting redundant at this point….). In summary, he states that although cooking may have adverse effects on the nutritional content of food (energy losses through drippings, the production of inedible compounds and a reduction in vitamins) it does make what nutrients remain easier to digest by breaking down the cell walls or plant matter and tenderizing meats (Wrangham, 2009). He asserts, at the end of the chapter, that because female members of the genius Homo cooked and could therefore get more nutrients, they had healthier babies, higher reproductive success and passed on more genes than ancient raw-foodists.

            The importance of consuming high-nutrition foods during pregnancy is clear. But in this day and age it may be taken too far.  New research done by the Royal Veterinary College of London suggests that food preferences can be passed down from mother to unborn child, especially those for high calorie, high sugar and high cholesterol foods. Their research found that rats that ate diets high in fat, salt and sugar while pregnant produced offspring who were more likely to prefer the same diet as opposed to regular feed (Boyal et al., 2008). Another study from the Journal of Physiology indicated that these young rats bodies’ retained negative effects to their metabolism long past their junk food filled-adolescence (Science Daily, 2008).

            Are there similarities between pregnant women and pregnant rats? Research shows that the heavier a woman became during pregnancy the more likely she was to have an obese child (Oken et al., 2008).  The same study shows the female children shows signs of high levels of leptin –the hormone that induces appetite, making them more susceptible to over eating.  Therefore, nutritionist Dr. Stephanie Bayol states: “We always say 'you are what you eat'. In fact, it may also be true that 'you are what your mother ate.' This does not mean that obesity and poor health is inevitable and it is important that we take care of ourselves and live a healthy lifestyle. But it does mean that mothers must eat responsibly whilst pregnant" (Science Daily, 2008).

            Wrangham states that passing nutrition and a preference for cooked food from mother to child with crucial in the success of our early ancestors (Wrangham, 2009). I find it interesting that now the same trend, plus Twinkies, little Debbies’ and Frittos, may again affect our evolutionary success. As obesity and related diseases occur with increasing frequency within the industrialized world, it will interesting to see if society’s attention switches from a fixation on slim-cut jeans, to addressing the genes themselves.

References:

Bayol S, Simbi B, Bertrand, and Stickland N. 2008. Offspring from mothers fed a "junk food" diet in pregnancy and lactation exhibit exacerbated adiposity which is more pronounced in females. The Journal of Physiology. 586:3219-3230.

Oken E, Taveras E, Kleinman, K, Rich-Edwards, J and Gillam M. 2008. Gestational weight gain and child adiposity at age 3 years.  American Journal of Obstetrics and Gynecology. 196:322.

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

--- 2008. Poor Diet During Pregnancy May Have Long Term Impact On Child's Health, Study Suggests. Science Daily. Available online at: http://www.sciencedaily.com/releases/2008/06/080630200951.htm