Book Report: Catching Fire: How Cooking Made us Human

This book is about the human use of fire during prehistory, and how it shaped us.

My own speculation (as opposed to what is actually in the book) is in brown italics.

Modern Raw Food Faddists

Some modern people choose to attempt a raw food diet, believing that this is how prehistoric people ate, and since we are thus theoretically evolved for it, a raw diet is more "natural" and will lead to greater health.
It should be noted that modern people attempting such a diet have a number of advantages over a prehistoric raw foodist. They have access to very sharp steel knives, blenders, and cuisinarts suitable for preparing food and breaking it down. They have access to supermarkets full of processed, easy to digest food. Furthermore, many people claiming to live on a "raw diet" actually heat some of their food slightly (to about 120 degrees Fahrenheit) which helps break it down a bit.
Nonetheless, people on raw diets observe the following effects

• They have trouble maintaining body weight. In our times, this is often seen as a good thing, but in prehistory, it would have been quite a bad thing. It would have been an especially bad thing for a pregnant woman.
• There is a drastic reduction in fertility:
• Half the women quit menstruating, becoming temporarily sterile. It is probable that those who manage to keep menstruating are experiencing a substantial drop in fertility.
• Men become less virile.
• Some raw foodists see this drop in fertility as a good thing, feeling that menstruation and ejaculation are ways the body gets rid of "toxins". Less frequent menstruation and ejaculation are thus evidence of less "toxins" in the diet. Look at the bright side of this: Such people are voluntarily removing themselves from the gene pool!

All modern primitive peoples had fire when discovered. I had heard that Tasmanian aborigines didn't have fire, but investigation showed they did, they just didn't know how to start it. If a tribe lost their fire, they borrowed some from a neighboring tribe.
The conclusion from all this is that a prehistoric homo sapiens tribe that lost its fire and couldn't reacquire it would be unable to maintain their fertility very well, would be unable to maintain their health well enough for the physically active prehistoric lifestyle, and would be unable to hold their own in warfare with neighboring tribes. Such a tribe would be doomed.

How Long Have We Been Cooking?

There are a few very ancient fire pits that look like humans started them, but these are extremely few and far between -- hearths are generally nowhere near as well-preserved as fossilized bones.
We do know a lot about the physiology of prehistoric people, however. Notable are three big changes in physiology between apes and homo sapiens:

• Our guts are smaller.
• Our jaws are considerably smaller. It should be noted that non-human primates often spend hours each day chewing their food.
• We don't have opposable toes. We can't climb trees anywhere near as well as our ape cousins. Apes usually sleep in trees. Sleeping on the ground in a jungle or forest is quite dangerous, as you are an easy target for predators. If we had fire, we could keep predators at a safe distance.

These changes were already substantial by the time homo erectus emerged -- about one and a half million years ago. So we would have had to be cooking our fire for a long time before that in order for these drastic changes in physiology to have had time to evolve.

How Did We Tame Fire?

I've wondered a lot about this. This was the main thing I wanted to learn from this book, and the author doesn't gives it as much attention as I would have liked.

Taming fire is difficult. You have to figure out that wood and leaves burn and that rocks, dirt and water don't. You have to figure out that dead wood and leaves burn better than green wood and leaves. You have to figure out that if you hold a branch that is burning at the end with the end pointing down, the fire spreads to the rest of the branch, while if you hold it upright, it doesn't. And you have to not start a forest or bush fire or inflict life-threatening burns on yourself while you figure all this out.

• One theory is that a fire might be caused by a lightning strike, and then people would get the fire from that. This just doesn't fly. A human would be lucky to see a single fire from a lightning strike in their lifetime. You couldn't learn how to tame fire well enough to keep it going from that one encounter in your life.
• Another theory is that people might get fire from a forest or bush fire. Again, this just doesn't seem workable. This is a rare occasion, and an emergency to boot. If you encounter a forest or bush fire, you are unlikely to survive if your response is anything other than to run at full speed in the opposite direction.

Clearly, to tame fire, we would have had to have regular, non life-threatening access to it over a long period of time. The author's answer is quite convincing: There is a type of rock that is a mixture of iron and sulfur known as pyrite, or "fool's gold". It is not extremely rare, and could be quite in abundance in some places. Banging such rocks together produces really good sparks. This could have been quite entertaining, and if done enough, could lead, over a long time, to learning how to tame fire. Eventually we would learn that food, especially meat, tastes better and is easier to digest if cooked. (When I was in the Boy Scouts, we were taught that one legitimate way to cook a steak was "caveman style", where you just throw it on the burning coals. I never actually tried this myself, though).

How Did Fire Affect Us?

Digesting raw food takes a lot of energy. Cooking food makes digesting easier frees up a lot of energy for other uses, such as larger brains.
Cooking could also help drive the evolution of larger brains. Keeping a fire going and not being injured by it is not easy, especially for a hominid with brains much smaller than ours. It was high tech for the time. Hominids with larger brains would have been more able to pull it off. As has been said, as we evolved more dependency upon fire, losing it would have been a major threat to a tribe's survival.
The author talks about human pair bonding being primarily oriented toward division of labor. A hunter could go out and cover a much larger radius if he could be confident a cooked meal was waiting for him when he got home.
He argues that a human man-wife team was more oriented toward division of labor and having one party be able to stay at the camp and cook while the other hunted, than reproduction. He cites, as evidence, a modern primitive tribe (one tribe) where the wives sleep around with their husbands' knowledge. The husbands don't like this, but put up with it. I really had trouble buying this, and I think it is more easily explained by bad anthropology by whoever studied that one tribe than anything else. He also didn't elaborate on how willing these husbands who had been blatantly cheated on were to make sacrifices for the well-being of the children of such unions.