"How does life work? How does nature produce the right numbers of zebras and lions on the African savanna, or fish in the ocean? How do our bodies produce the right numbers of cells in our organs and bloodstream? In [this book], ... Sean Carroll tells the stories of the pioneering scientists who sought the answers to such simple yet profoundly important questions, and shows how their discoveries matter for our health and the health of the planet we depend upon"--Dust jacket flap.
However, despite enjoying this book immensely, I can’t help but share how ultimately sorely disappointed I was at the author’s Pollyanna optimism in the end when (very briefly) applying these rules to the health of the planet and the future of life thereon…especially human life. He defended his overt optimism by citing Greg Carr (the American entrepreneur and philanthropist who is primarily responsible for the restoration of Mozambique's Gorongosa National Park) by saying: “Choose optimism because the alternative is a self-fulfilling prophecy.” He’s a scientist; shouldn’t he choose realism? Look almost everywhere and it is so obvious that humankind—mostly by its sheer numbers—is pushing major planet-level natural regulatory systems to the breaking point. Is it not hubris to think that humanity may be able to fix all these complex adaptive systems that we’ve already set careening out of balance and many that we do not yet know we have set out of balance? Personally, I don’t choose either optimism or pessimism; I do choose realism. Doing so does not stop me from enjoying the present moment and still doing whatever I can to make a better future for life on Earth…i.e., to try to do my small part to try to keep the world and its countless array of complex adaptive biological and ecological regulatory systems in balance.
The theme of Serengeti Rules is the regulation of systems. Absolutely everything plays a role in keeping the entire ecosystem in balance. When one element goes rogue, it can destroy the entire system. Sean Carroll spends a great deal of time explaining examples at the microscopic level of human biology – from bacteria to cancers. When something gains too much power, it becomes toxic to the system. Homeostasis is upset, and we fall ill. So with the external world and its ecosystems. But it is only in the last half of the book that Carroll finally returns to the Serengeti to show how it works on a large scale. This is an enormously common fault in nonfiction of late. It leaves readers fidgety, wondering when the author is going to honor the title of the work.
The first 130 pages here are stories about various scientists who discovered the relationships among the microscopic components of our bodies. How they were precocious children and students, how they stumbled onto their discoveries, and how they (and it’s usually someone else) leveraged them into new drugs and other treatments. The Serengeti will have to wait.
At the Serengeti level, the fundamental driver of the natural order is trophic cascades, more colloquially understood as the food chain. Take one element out of the food chain and the house of cards can collapse. The upset can come from above or below: not enough vegetation means not enough prey. Removal of the top predator can lead to overwhelming numbers of prey, which leads to vegetation shortages, different (wrong) vegetation taking over, inappropriate habitats for animals….
Carroll includes my favorite example. Off the west coast of North America, the undersea kelp forests have been disappearing, removing an important habitat for all kinds of underwater animals. The reason the kelp is gone is because sea urchins have been swarming over the sea floor, cleaning it of all the kelp. The reason the sea urchins are out of control is that while they are the sea otter’s favorite food, the otters are running for cover elsewhere. The reason the sea otters are gone is because unusually, killer whales have moved inshore to hunt them. The reason the killer whales have invaded is because their normal prey of sea lions is in major decline. And of course, the reason the sea lions are in decline is because of us, overfishing so that fish stocks are down 90%. A shortage of sea lion food. That’s all it took to upset the entire balance. Multiply that throughout the world, and you begin the see the mess we’ve made.
The book ends on a positive note, with the rehabilitation of a wilderness park in Mozambique, and inspiring achievements in the eradication of smallpox and polio. It can be done if we have two key factors in place: good management and good policing. Finding those two elements together is an achievement by itself.