The Wild Life of Our Bodies

September 15, 2012

Book Shelf

 

The Wild Life of Our Bodies: Predators, Parasites, and Partners That Shape Who We Are Today

By Rob Dunn
HarperCollins, $26.99

Reviewed by Muriel Strand

Do we really have that much in common with Ardi, the protohuman who lived in Africa 4.4 million years ago? More than you might think, according to North Carolina state biology professor Rob Dunn.

To explain why and how this matters, he serves up plenty of intriguing science stories about natural ecology, along with some speculations about various human traits such as smooth skin, and scary stories, all in supple prose that keeps the pages turning.

Dunn describes how biological and human cultural evolution have led us out of Eden, away from Ardi’s hunter-gatherer lifestyle, and into domestication and various modern health problems.

Some notable maladies are side effects of living rather differently than we originally evolved to live, and apparently did live until perhaps 10,000 years ago when agriculture appeared worldwide. As a result, if Ardi came to visit she would probably ask, “Where are all the plants and animals?”

First up is the rather creepy probability that parasite animals can be good for you. There is growing evidence that certain intestinal worms that have co-evolved with humans can help certain people, notably sufferers of Crohn’s disease, which can get bad enough that ‘worming’ yourself can feel less creepy. And some cases of diabetes, heart disease, and asthma may apparently benefit from this therapy.

But how can this be? Well, not all parasites are pathogens, where the host suffers as the parasite thrives. Some are mutualists (both parties benefit) and others are commensals (the parasite benefits but the host is unaffected). Our immune systems evolved to interact usefully with all three kinds.

It turns out that our immune systems can respond both peacefully and aggressively toward tiny immigrants. If a parasite survives initial antibody defenses, other ‘peacekeeper’ bodies arise to balance the body’s response and “reserve the body’s energy to fight another day against a more beatable or virulent foe.” Unfortunately the modern war on germs idles the peacekeepers, leaving them too weak to keep our aggressive antibodies in balance, opening the door to various auto-immune diseases.

But what about Ardi? What’s the essential difference between proto and human? Dunn suggests that when “we decided to kill a species not for food or in self-defense, but instead in order to control what lived and did not live around us, when we did that, we were then fully human.”

In other words, Ardi was wild and we’re not (although some of us are more domesticated than others.) Now there are definite advantages to a little domestication, like not being eaten by bears.

But people don’t always know when or how to stop. Agriculture has wandered far from wildness and shows few signs of returning. Though farming is usually seen as progress, the paleo-archaeological record presents skeletons rather more stunted than those of previous hunter-gatherers. Another unintended consequence of agriculture is permanent settlements where pests such as rats and fleas become permanent too.

So how wild should we be, optimally? Individual survival is favored by expedient solutions that are marginal and small but may be cumulatively negative for the species and the ecosystem.

A big problem with marginal solutions such as germicides or pesticides is they kill the weak or slow but always leave some which are strong or weedy or otherwise wild and obviously go on to reproduce. Disturbances create the vacuum nature abhors, and opportunists are favored.

Finally, Dunn asks, “What can we realistically do to restore the good elements of nature to our lives?” Observing that other farming species such as ants live near their crops for control and hygiene, he tells the story of pessimistic Professor Despommier, whose students insisted on hope, on ideas and solutions rather than the predictable ecological gloom and doom. When, skeptical, he invites them to look for possibilities, their learning path draws him in despite himself and one day inspires him to say “What if we turned whole buildings into farms?”

Dunn explains how this concept really isn’t crazy, even if you plan to convert office towers. It offers rational hope for the survival of the seven billion of us who are here now. But it doesn’t tell us how much wildness is optimal. More undomesticated research and development is in order.

Muriel Strand is a Sacramento-based blogger and engineer.


* From the quarterly newsletter SEJournal, Summer/Fall 2012. Each new issue of SEJournal is available to members and subscribers only; find subscription information here or learn how to join SEJ. Past issues are archived for the public here.