Tuesday, December 28, 2010

Reading :: Catching Fire

Catching Fire: How Cooking Made Us Human
By Richard Wrangham

Perhaps a year ago, I read an excerpt from this book, whose hypothesis immediately intrigued me. After waiting for a long time for it to become available at the library, I bought the book on the Kindle. No pun intended.

What's the book's hypothesis? In a nutshell: cooking is what made us human. More precisely, Homo Erectus emerged as a byproduct of learning to cook, and therefore the genus Homo owes its entire existence to cooking. No cooking, no human beings.

This is a rather contested hypothesis. As Wrangham explains, the accepted story is that cooking came much later, and the evolution of Homo is usually attributed to meat eating. Some people, such as raw foodists, even claim that cooking is bad for us. But Wrangham marshals several points in favor of his theory:
  • Cooked foods release more calories than raw ones. For instance, the human body absorbs about 95% of starch in potatoes by the time the food matter reaches the ileum. For uncooked potatoes, that number plummets to 51%. You have to eat almost twice as many raw potatoes as cooked ones to get the same benefit. In fact, great apes eat about twice as much per day as we do, by weight. Interestingly, apes - and other animals - prefer food cooked.
  • Human beings have much shorter intestines than other animals. We can't extract the same amount of calories from raw foods. We also have smaller mouths, weaker jaws, smaller teeth, and smaller stomachs.
  • Human beings' brains are proportionally the largest in the animal kingdom, about 2.5% of our body weight, but using 20% of our basal metabolism rate (compared to 8-10% in other mammals).
  • Human beings are more resistant to Mailard compounds than other animals. (Mailard compounds are carcinogens that result from cooking.)
  • Cooking is practiced by every known human society.
  • Those who subsist on raw food alone report feeling hungry all the time, as well as negative impact on their sexual functions: a rate of infertility greater than 50%.
  • Human beings spend about 5% of their day chewing. If we were to eat only raw food, Wrangham estimates that we would be chewing for about 42% of the day (just over 5 hours). The average calorie intake for a human being is over six times that of a chimpanzee. (At this point, I thought about Clay Shirky's argument in Cognitive Surplus.)
Wrangham argues that given the above, we couldn't evolve without cooking. The numbers don't add up: Raw food simply doesn't give enough calories to support our massive energy-hungry brains, and our small mouths and teeth aren't up for the task of processing it at any rate.

In Wrangham's view, our ancestors enjoyed three evolutionary leaps due to food. First, they began chewing meat along with a rough leaf, which provided additional traction and helped to break down the food. (Chimpanzees do this today, and Wrangham describes persuading his friends to imitate the chimps with raw goat meat and leaves.) Second, they began pounding the meat to tenderize it, using logs or rocks. (Chimpanzees use rocks to smash open nuts, and we've found habiline remains next to crude stone hammers.) Finally, they began cooking. Wrangham pegs each advance to a corresponding increase in cranial capacity: the more our ancestors processed food, the more they could get from it, meaning that they could support larger brains and smaller guts.

So that's the basic argument, and I found it fascinating, although I don't have the background to properly judge it. This argument could have fit into a smaller book or even an article, but Wrangham expands it considerably in a few ways, not all good.

First, he adds several anecdotes that don't always hit the mark: for instance, he recounts a very few known incidents in which people had to survive on raw food and compares them to many anecdotes in which people elected to, for instance, cook each other. You would think that these anecdotes would be fascinating, but they're so dense here that I felt as if I were reading Ripley's Believe it or Not.

Second, in Ch.6-7 he speculates that cooking is at the root of the division of the sexes, a fairly standard interpretation in the vein of evolutionary psychology. I think Wrangham overreaches here.

Third, and more generally, Wrangham tends to go over the same ground a lot. We are repeatedly treated to information about how small human intestines, jaws, and teeth are, how big our brains are, how much cooking changes raw food. A good ruthless edit could have streamlined the book considerably.

Still, the book's fascinating and it's easy to read. I raced through it. If what I've outlined sounds like what you'd like to read, take a look.


Now a quick aside. This is the first book that I read in its entirety on my phone, a Nexus One running Android. I used the Kindle application, which, unlike Google's eBooks, allows bookmarking, highlighting, and notes. Recently I blogged about my worries regarding reading strategies in ebooks, so this book provided a good chance to try out some new strategies.

In general, the results were positive. My eyesight is still good, so I made the font as small as possible, increasing the number of words on the page. The Kindle's highlighting and notes are good, good enough to replace the sticky notes I usually use. I appreciated that my reading progress and notes synched across platforms, so when it was time to write this review, I simply fired up the Kindle app on my netbook and got started. The Kindle's search feature was also very useful for looking up various topics that I had forgotten to tag in the notes. And, of course, I didn't have to carry the book. Nor did I have to wait for it to be delivered.

On the other hand, I have plenty of complaints. One is that the Kindle doesn't allow me to copy from the text or highlighting. I understand that they're trying to keep me from infringing copyright, but they also keep me from copying fair-use passages. Another is that the Kindle doesn't have page numbers. If you want to find out where the information above comes from, you'll have to search the book as I did. A third issue was that, since the Kindle doesn't use page numbers, the progress bar was misleading: I finished the book at the 50% mark and discovered that the rest of it was end matter, including the (useless) index.

That being said, I have been relieved at how relatively painless reading this book on the Kindle app turned out to be. For books that cost more in print + shipping, particularly ones that I can't find in a used book store, I'll certainly consider the Kindle. I can't say the same for Google's eBooks at present.