The myth of the golden age dies hard. People who espouse a Paleo lifestyle speak in terms of evolution, but the overall framework of their beliefs strikes me as being modeled surprisingly closely on earlier stories of a golden age, a fall, and attempts to live in accordance with the rules that will return us, at least to some degree, to the golden age. The complexities of evolution are smoothed out, and the story of human evolution is forced awkwardly into a much older narrative.
Marilyn Zuk’s book is a bracing corrective that explains how the Paleo picture is at odds with the way humans have really evolved (and continue to evolve). It’s not only informative but witty and even laugh-out-loud funny in spots.
Zuk begins by outlining the ways that human evolution is often misunderstood. The short version: Evolution is complicated. First, it can happen much more quickly than we often realize. Second, we never stopped evolving, although not everything about us is evolving at the same rate. We’re not really Fred Flintstone living in Manhattan, and we’re not “stuck with” a brain or a body or a set of genes that has been unable to “catch up” to current conditions. Different parts of the genome change at different rates under different circumstances.
It’s less meaningful, Zuk points out, to look at how genes differ or are the same between species of within a species over time than it is to ask which ones changed quickly, and why. The idea of a baseline human nature (or chimp or bonobo nature, for that matter) that we can use for comparison is not really all that helpful.
There’s also no reason to believe that humans were ever perfectly adapted to their environment. Zuk quotes François Jacob: “Nature is a tinkerer, not an engineer.” We’ve always been, and continue to be, a work in progress, with all the trade-offs involved in working within the limitations of what’s already there. Once you look at the story of human evolution that way, you see that it’s hard to put a finger on a perfect time when we were very well fitted to our environment and to try to replicate that environment. We’ve always been a series of kludges that worked well enough most of the time.
On top of that, because different parts of the genome evolve at different rates, there isn’t even a single environment that shaped all of our characteristics. Zuk argues that you need to think in terms of the environment that affected a particular trait rather than tracing everything back to the savanna. (Although it can be hard to pin down the landscape and circumstances in which a particular adaptation occurred because humans have lived in so many different environments, even before the advent of agriculture and the technologies that enabled us to live pretty much anywhere.)
Within this framework, Zuk examines diet, exercise, illness and health, how men and women behave and relate to each other, and how people raise families.
Regarding diet, for example, she discusses the relatively recent adaptation that enables adults to drink milk (which, I learned, is actually two different genetic changes in European and African populations, an example of convergent evolution). She also says that humans didn’t have a single diet between the emergence of the genus Homo and the rise of agriculture. In any case, it’s hard to draw a line regarding pre-agricultural and post-agricultural humanity because there are different types of agriculture—horticulture, pastoralism, and intensive agriculture—and it’s not clear when some of the changes in humans related to intensive agriculture began to appear.
Overall, this excellent book taught me a lot about the subtleties and complications of human evolution, and it was great fun to read. On a deeper level, I think it fosters a better understanding of the fuller implications of being evolved, and evolving, creatures for whom there was, and will be, no golden age.