Humans and apes separated about 6 million years ago, and ever since then humans have been careering down an evolutionary path all their own. Lucky for us, bits of bones dropped along the way became fossilized, and these remains tell much about the physical evolution of the creatures that eventually became modern humans.
Harder to follow is the path of our behavior. No one really knows what early humans acted like, who they interacted with or what kind of social groups they preferred, and so the lifestyle of our ancient ancestors is only a guess. This part of our history is so up for grabs that there is lots of room for speculation by polymaths curious enough to read the mountain of anthropological literature and piece together a credible story of human behavioral evolution.
And why not? Anthropology has a long tradition of letting others look at the data. Authors like Robert Ardrey, Elaine Morgan, Carl Sagan and Jared Diamond, among many others, have all attempted to figure out where we came from and how we did it. Because no one could possibly be right -- we have no film from the Pleistocene and no written records of our ancient past to confirm or refute anything anyone says -- each account has merit and is worthy of discussion.
Leonard Shlain, a surgeon, is the latest to jump in with Sex, Time and Power, in which he makes a case for concentrating on women and their need for the mineral iron as the key to understanding our past. Women need high stores of iron, Shlain says, because they menstruate every month, become pregnant and nurse. In our evolutionary past the best way to restore depleted iron was to eat meat. But women were probably not hunters, and so they must have manipulated men with sexual favors to bring home a blood-soaked dinner. This manipulative move, Shlain suggests, then set into motion just about every aspect of human behavior.
The reproductive biology of women supposedly supports his account: Menstruation, with a blood loss excessive compared with that of other mammals, makes women crave meat. Women have also lost the usual advertisement of fertility -- heat -- and are always open to sex. Men, who have high levels of testosterone, which increases their sex drive, are then lured into hunting and sharing meat by the promise of continuous sex from these menstruating, sexy women. The trade is meat for sex and everyone wins as genes are passed down by the iron-rich women who produce healthy, intelligent babies.
The female lust for meat, Shlain suggests, is responsible for the evolution of much of human behavior, including intimate relations between men and women, foresight and puzzle solving, complex social interactions, different psychological moods between men and women, and any number of human traits that we now see in the best and worst of us.
Shlain's account is supported by endless references to every human biological and behavioral feature that has ever been written about; he certainly has an exhaustive reading list. But everything he suggests, except for the specific detail of a need for iron, has been said before, which gives his account an old-fashioned feel.
Meat for sex? We've been hearing about this since the 1960s. Men like sex and woman just want to make babies? Hasn't this been a party line since the 1950s? Even Shlain's enthusiasm for women as the prime movers of humanity (but thanks for thinking of us) comes off as dated given that female anthropologists like Sarah Blaffer Hrdy, Helen Fisher, Alison Jolly and many others have been writing about this for years.
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