Moalem’s book draws on a wide array of scientific research and studies—crucially, though, Moalem doesn’t simply focus on studies about genetics and evolution. Instead, he demonstrates how research on a completely disparate topic might actually provide essential insight into our genetic development. And because there is so much that we still do not know about how our genes have developed, he argues that we need to continue asking questions and conducting research in all fields. That research, Moalem suggests, might in turn help us find new information about evolution and give us new ways to treat disease and illness, and vice versa: research on evolution can also unlock the key to scientific discoveries in other fields.
First, Moalem delves into how studying adaptations in plants and animals can provide insight into similar adaptations in humans. Studies of how plants and animals react to freezing helps us understand why diabetes may have insulated humans from colder temperatures during the Younger Dryas, the last period of extremely cold weather, and can lead us to develop better techniques for organ transplant. To illustrate this, Moalem discusses the frozen grapes that are used in ice wine, a drink that was created by accident 400 years ago by a German winemaker who waited too long to harvest the grapes; in the late autumn, the winemaker’s fields were hit by a sudden frost. The grapes were shrunken, but when the winemaker harvested them, they were incredibly sweet. Subsequent studies proved that this was due to two different reactions: first, the grapes were trying to offload water so that they did not freeze and die. Second, sugar is also a natural antifreeze, so they were retaining sugar to lower their freezing point to survive. This provided a potential explanation for cold diuresis, the phenomenon in which humans urinate more frequently in cold temperatures (in order to similarly offload water). It also explained why humans might have developed diabetes: to fill the blood with sugar as our own natural antifreeze during the Younger Dryas. Some animals do the same thing: the wood frog lives across North America, all the way up to Alaska. Rather than hibernating and insulating itself in the winter, the frog freezes solid. It has no heartbeat, breathing, or measurable brain activity. Yet a few minutes after rising temperatures thaw the frog, it sparks into gear. It is able to do so because it has flooded glucose into its bloodstream, lowering its freezing point. The ice, on the other hand, has been sandwiched around its organs to keep them as cool as possible without actually being frozen or damaged. Understanding the wood frog not only provides us with evolutionary clues on why diabetes became an inherited trait, but it could also lend itself to the development of future techniques to freeze and transport organs for donation.
Research on babies birthed in the water also provide key insights as to how we might have evolved from our pre-human predecessors. Studies conducted in 1999 and 2005 show that water births tend to be shorter, less painful, and with less rate of infection. Babies don’t breathe until they feel air on their face, mitigating the fear of drowning and also protecting them from inhaling fecal matter or “birthing residue” that can cause an infection in their lungs during conventional deliveries. These studies offer some evidence for a controversial theory called the “aquatic ape” theory, which was first theorized by Alister Hardy. Hardy suggested that we may have descended from an ape that was aquatic or semi-aquatic, and the contemporary studies suggesting that human birth is better suited for water than land provides give new credence to older theories of evolution.
The reverse has also proven true: studies of evolution can also lead to the development of improved medications and medical practices for humans, showing a reciprocity of information from evolutionary research to other fields as well. Studies of plant evolution have illustrated that certain plants, like sweet potatoes and clovers, produce phytoestrogens, which serve as a defense mechanism for plants because they interfere with animals’ reproductive systems when they are eaten. Chemist Carl Djerassi based the development of the birth control pill on this kind of chemical production by plants, modeling his chemicals on the Mexican yam. Thus, research in plant evolution has allowed humans to create medical innovations as well. Recognizing how viruses and infectious agents select for or against traits that harm their hosts can help us “influence the evolution of parasites away from virulence” (the degree to which an organism destroys its host). An example of this is cholera, which can spread through humans or through water. If sewage flows easily into rivers that people wash in or drink from, then the cholera strain would evolve toward virulence because it can multiply freely without humans and rely on its access to the water supply for transmission. But if a country develops ways to protect its water supply, the bacteria “should evolve away from virulence”—that is to say, if a bacterium needs a human to be mobile in order to spread, the disease will be less fatal. The implications of this are enormous, as Moalem writes, "instead of challenging bacteria to become stronger and more dangerous through an antibiotic arms race, we could essentially challenge them to get along with us.” In this way, learning about evolutionary pressures on organisms like bacteria can ultimately help us learn to combat them.
Moalem ends Survival of the Sickest with the assertion that his book is all about questions—the first being, “Why?” and the second being, “What can we do with that?” Moalem emphasizes the need to be curious and to pursue research, both in evolutionary science and in other fields. As he demonstrates repeatedly throughout the book, developing science in all fields can open up new avenues of understanding about where we’ve come from, where we might be going, and how we can use that information to improve our future.
Related Themes from Other Texts
Interdisciplinary Science and Research ThemeTracker
Interdisciplinary Science and Research Quotes in Survival of the Sickest
Today, we know that Aran suffered the effects of the most common genetic disorder in people of European descent—hemochromatosis, a disorder that may very well have helped his ancestors to survive the plague.
Today, Aran’s health has been restored through bloodletting, one of the oldest medical practices on earth.
Today, we understand much more about the complex interrelationship of our bodies, iron, infection, and conditions like hemochromatosis and anemia.
So when the grape dumps water at the first sign of frost, it’s actually protecting itself in two ways—first, by reducing water volume and second, by raising the sugar concentration of the water that remains. And that allows the grape to withstand colder temperature without freezing.
Instead of worrying about whether or not there are distinct “races,” let's concentrate on what we do know and use that to advance medical science. What we do know is that distinct populations do share distinct genetic heritages, which are almost certainly the result of different evolutionary pressures our various ancestors experienced as they settled and resettled across the globe.
The next time you’re looking for some convenient birth control, you don’t have to snack on a field of clover, of course. But if you take many forms of the famous “Pill,” you’re not doing something all that different. The gifted chemist Carl Djerassi based his development of the Pill on just this kind of botanical birth control. He wasn’t using clover, though; he was using sweet potatoes—the Mexican yam to be exact.
Former president Jimmy Carter has led a two-decade effort to spread understanding about the parasite’s method of reproduction to every corner of the world, ensuring that its victims avoid water when looking for relief and that its potential victims avoid water that could be infected. According to the Carter Center, the worldwide incidence of Guinea worm infections had dropped from 3.5 million in 1986 to just 10,674 in 2005.
Ewald believes that we can use this understanding to influence the evolution of parasites away from virulence. The basic theory is this—shut down the modes of transmission that don’t require human participation and suddenly all the evolutionary pressure is directed at allowing the human host to get up and get out.
By introducing the harmless virus to our bodies, we stimulate our immune systems to produce antibodies specifically tailored to defend against that virus. Then, if we are exposed to the harmful version, our bodies are prepared to defend themselves immediately.
Essentially, one or more of the compounds in the vitamin supplements fed to the expectant mothers reached down into the mouse embryos and flicked the agouti gene into the “off” position. When the baby mice were born, their DNA still contained the agouti gene, but it wasn’t expressed—chemicals had attached to the gene and suppressed its instructions.
Here’s the first thing we don’t know—we don’t have anywhere near a complete understanding of which genes are turned off or turned down by which methyl donors. For example, methylation of a gene that influences hair color might lead to a harmless change—but the same process that triggered methylation of the hair color gene may also be suppressing a tumor suppressor.
That still doesn’t explain the lack of evolutionary pressure against bipedalism and the accompanying reproductive risk caused by the change in pelvic shape. Unless—what if the water changed the equation somehow and made the process easier? If the water made the birthing process easier, then most of the evolutionary pressure would favor the advantages those aquatic apes gained from the shift to two feet.
I hope that you’ll come away from this book with an appreciation of three things. First, that life is in a constant state of creation. Evolution isn’t over—it’s all around you, changing as we go. Second, that nothing in our world exists in isolation. We—meaning humans and animals and plants and microbes and everything else—are all evolving together. And third, that our relationship with disease is often much more complex than we may have previously realized.
