Reading 49

Cooked Food

This passage is adapted from an article by Mary Evans that originally appeared in The Economist (© 2009 by Mary Evans).

  1. You are what you eat, or so the
  2. saying goes. But Richard
  3. Wrangham, of Harvard
  4. University, believes that this
  5. is true in a more profound
  6. sense. It is not just you who
  7. are what you eat, but the
  8. entire human species. And
  9. with Homo sapiens, what
  10. makes the species unique in
  11. Dr. Wrangham’s opinion is
  12. that its food is so often cooked.
  13. Cooking is a human universal.
  14. No one other than a few
  15. faddists tries to survive on
  16. raw food alone. And the
  17. consumption of a cooked
  18. meal in the evening is normal
  19. in every known society.
  20. Moreover, without cooking,
  21. the human brain could not
  22. keep running. Dr. Wrangham
  23. thus believes that cooking and
  24. humanity are coeval.
  25. In fact, as he outlined to the
  26. American Association for the
  27. Advancement of Science, in
  28. Chicago, he thinks that cooking
  29. and other forms of preparing
  30. food are humanity’s “killer
  31. app”: the evolutionary change
  32. that underpins all of the other
  33. changes that have made people
  34. such unusual animals.
  35. Humans became human with
  36. the emergence of a species called
  37. Homo erectus. This had a
  38. skeleton much like modern man’s
  39. —a big, brain-filled skull and a
  40. narrow pelvis and rib cage, which
  41. imply a small abdomen and thus
  42. a small gut. Hitherto, the
  43. explanation for this shift from the
  44. smaller skulls and wider pelvises
  45. of man’s apelike ancestors has
  46. been a shift from a vegetable-
  47. based diet to a meat-based one.
  48. Meat has more calories than
  49. plant matter, the theory went.
  50. A smaller gut could therefore
  51. support a larger brain.
  52. Dr. Wrangham disagrees. When
  53. you do the sums, raw meat is
  54. still insufficient to bridge the
  55. gap. He points out that even
  56. modern “raw foodists,” members
  57. of a back-to-nature social
  58. movement, struggle to maintain
  59. their weight—and they have
  60. access to animals and plants
  61. that have been bred for the
  62. table. Pre-agricultural man
  63. confined to raw food would
  64. have starved.
  65. Start cooking, however, and
  66. things change radically. Cooking
  67. breaks starch molecules into
  68. more digestible fragments. It
  69. “denatures” protein molecules,
  70. so that their amino-acid chains
  71. unfold and digestive enzymes
  72. can attack them more easily.
  73. And heat physically softens
  74. food. That makes it easier to
  75. digest, so even though the
  76. stuff is no more calorific, the
  77. body uses fewer calories dealing
  78. with it.
  79. In support of his thesis, Dr.
  80. Wrangham, who is an
  81. anthropologist, has ransacked
  82. other fields and come up with
  83. an impressive array of material.
  84. Cooking increases the share of
  85. food digested in the stomach
  86. and small intestine, where it
  87. can be absorbed, from 50% to
  88. 95% according to work done
  89. on people fitted for medical
  90. reasons with collection bags at
  91. the ends of their small intestines.
  92. Another telling experiment,
  93. conducted on rats, did not rely
  94. on cooking. Rather the
  95. experimenters ground up food
  96. pellets and then recompacted
  97. them to make them softer. Rats
  98. fed on the softer pellets weighed
  99. 30% more after 26 weeks than
  100. those fed the same weight of
  101. standard pellets. The difference
  102. was because of the lower cost
  103. of digestion. Indeed, Dr.
  104. Wrangham suspects the main
  105. cause of the modern epidemic
  106. of obesity is not overeating
  107. but the rise of processed foods.
  108. These are softer, because that
  109. is what people prefer. Indeed,
  110. the nerves from the taste buds
  111. meet in a part of the brain called
  112. the amygdala with nerves that
  113. convey information on the
  114. softness of food. It is only after
  115. these two qualities have been
  116. compared that the brain
  117. assesses how pleasant a
  118. mouthful actually is.
  119. The archaeological evidence for
  120. ancient cookery is equivocal.
  121. Digs show that both modern
  122. humans and Neanderthals
  123. controlled fire in a way that
  124. almost certainly means they
  125. could cook, and did so at least
  126. 200,000 years ago. Since the
  127. last common ancestor of the
  128. two species lived more than
  129. 400,000 years ago, fire-control
  130. is probably at least as old as
  131. that, for they lived in different
  132. parts of the world, and so could
  133. not have copied each other.
  134. Older alleged sites of human
  135. fires are more susceptible to
  136. other interpretations, but they
  137. do exist. And traces of fire are
  138. easily wiped out, so the lack of
  139. direct evidence for them is no
  140. surprise. Instead, Dr.
  141. Wrangham is relying on a
  142. compelling chain of logic. And
  143. in doing so he may have cast
  144. light not only on what made
  145. humanity, but on one of the
  146. threats it faces today.