Most helpful positive review
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A brilliant and important hypothesis
on June 9, 2009
Around 1.8 to 1.9 million years ago, Homo habilis (a chimpanzee-like primate, but with a bigger brain and tool-making skills) evolved into Homo erectus. The changes were spectacular: Homo erectus had a 40% larger brain than Homo habilis; looked much more like a modern human than a chimpanzee; had lost its tree-climbing skills, but gained running skills; had a much smaller, and less energy-consuming digestive system (smaller mouth, teeth, jaws, jaw muscles, stomach, and colon); lost most of its coat of fur; and developed a social system based on economic cooperation: the husband hunted, the wife gathered and cooked, and they shared the food.
Wrangham argues that Homo habilis learned to control fire and that that fact is both a necessary and sufficient explanation for this evolutionary leap.
First, fire is used for cooking, as all primates find cooked food more delicious (even monkeys know to follow a forest fire to enjoy the cooked nuts). Cooking gelatinizes starch, denatures protein, and softens all foods, permitting more complete digestion and energy extraction. As a result, the food processing apparatus shrinks, freeing energy to support a larger brain. (After the gut shrinks, the animal can no longer process enough raw food to survive, but is dependent on cooking. Wrangham reports that humans with even a large supply of well-processed, high-quality food lose both weight and reproductive capacity on a raw diet, and that there are no known cases of a modern human surviving on raw food for more than a month.)
Second, fire provides defense against large carnivores, permitting Homo erectus to descend from the trees and live on the formerly preditor-dangerous ground. The group would sleep around the campfire while an alert sentinel watched for predators, which would be repelled with a fiery log. Living on the ground led to the development of long legs and flat feet--ideal for running.
Third, fire permits loss of fur, as a hairless animal could warm itself by the fire. Hairless animals can dissipate heat much more quickly, giving them the ability to outrun furry animals. Homo erectus could simply chase a prey animal until it collapsed from heat exhaustion.
Fourth, cooking permits specialization of labor. Without cooking, both males and females must spend most of their day gathering and chewing vegetable matter. Because hunting success is unpredictable, they could devote relatively little time to it, because an unsuccessful hunter would have inadequate time to gather and chew vegetables. Cooking, however, reduces chewing time from 5 hours per day to 1 hour, freeing time to hunt. A hunter who returned empty-handed could still enjoy a cooked vegetable meal and have time to eat it.
Here Wrangham (who teaches, inter alia, a course named "Theories of Sexual Coercion") indulges in academic feminism when he says that "cooking freed women's time and fed their children, but also trapped women into a newly subservient role enforced by male-dominated culture" as if this were a diabolical choice by patriarchal males. A more neutral explanation for the emergent sex roles might be as follows: Females, with their noisy, not-very-portable suckling infants and toddlers, cannot hunt because hunting is necessarily a stealthy and mobile activity. Therefore, males do the hunting. Because both hunting and cooking are time-consuming activities, males cannot do both. Therefore, females do the cooking. (They are trapped into cooking not by males but by their mammary glands.)
The various effects of control of fire were mutually reinforcing, leading to rapid evolutionary changes, resulting ultimately in modern humans.
Interestingly, Charles Darwin, while calling fire-making "probably the greatest [discovery], excepting language, ever made by man," thought that cooking was a late addition to the human skill-set without biological or evolutionary significance, and anthropologists agreed with him until quite recently.
The main text of the book comprises just 207 widely spaced pages, yet is somewhat repetitive. It includes many entertaining, if sometimes marginally relevant, anecdotes and a gratuitous chapter on contemporary food labeling and healthy eating. Despite these nits, I award 5 stars because Wrangham's cooking-makes-the-human hypothesis is both brilliant and important and the book is a highly enjoyable read.