Survival of the Sickest: Chapter 8 Summary & Analysis

At 12 years old, Seth Cook is the oldest living American with a rare genetic disorder called progeria, in which children age at a rate of 10 times the speed of people without it. By the time a baby with progeria is about a year and a half old, their skin starts to wrinkle, their hair starts to fall out, and they develop cardiovascular problems and degenerative diseases. Most people who have progeria die in their teens.

In April 2003, researchers isolated the genetic mutation that causes progeria: a defect in a protein   called lamin A that provides structural support for cells. With the mutation, cells deteriorate much more rapidly. In 2006, another team of researchers connected lamin A to normal human aging. The implications of this are significant, as it provides some clue as to why aging occurs. Scientists continue to debate what causes aging: whether it is wear and tear over the years or a product of evolution. Progeria suggests that aging is preprogrammed.

In the 1960s, Scientist Leonard Hayflick discovered in that cells can only divide a fixed number of times (52 to 60 times) before the cell division becomes an issue (known as the Hayflick limit). Every time a cell reproduces it loses DNA; in order to prevent the loss of important information, chromosomes have extra inconsequential DNA at their tips (called telomeres) so that they do not lose essential information. After that fixed number of times, cells start to lose more important DNA. But this limit serves an evolutionary purpose: it guards against cancer.

Cancer is a family of diseases characterized by uncontrollable cell division and growth. There are many lines of defense in the body against cancer, including the Hayflick limit. However, cancer cells have developed an enzyme called telomerase, which can lengthen the telomeres at the ends of chromosomes, so that there’s less loss of genetic information and cells can reproduce forever.

There are other evolutionary explanations for aging mechanisms: the Hayflick limit doesn’t explain why different animals have vastly different life expectancies. Moalem notes that in mammals, there’s a close correlation between size and life expectancy in different species. This is likely because a species with a greater risk of being eaten or greater environmental threats faces evolutionary pressure begin reproducing at an earlier age so that future generations mature faster. A shorter lifespan also allows species to evolve faster, because there is a shorter length of time between generations.

Moalem writes that programmed aging confers an evolutionary benefit on the species, like a biological version of planned obsolescence. He compares humans to iPods, which some people accused Apple of designing with planned obsolescence, so that the batteries would only last about 18 months. Similarly, by clearing out older models of humans, aging can make room for new models. Aging can also protect the group by removing individuals who are more likely to have diseases. Reproduction, by contrast, is how species are upgraded.

The prospect of programmed aging opens a door to possibilities like learning how to inhibit telomerase in cancer cells so that they cannot reproduce indefinitely—or to rebuild lamin A so that aging in people with progeria (or even people without it) might be reversed.

Moalem next explores how humans have evolved to give birth in the way that they do. Childbirth in humans is riskier, longer, and more painful than in our genetic cousins. This is due primarily to two factors: humans have large brains, and humans are bipedal. The fact that we have evolved to walk on two feet has made the pelvis more narrow, and the fact that we have evolved to have bigger brains makes it more difficult to squeeze through a mother’s pelvis. Because the human birth canal isn’t one constant shape, fetuses also have to twist their way through it and usually face away from the mother, which makes it difficult to give birth without assistance.

Moalem then examines our evolution into humans as a whole: where once we were furry and walked on all fours, we gradually lost our hair and walked upright. The conventional theory on how this happened is called the “savannah hypothesis,” which holds that prehumans moved out of the forest and into the savannah, perhaps because of environmental change. They had to find a new way to get food, leading them to start hunting. This led our ancestors to walk upright so they could scan the horizon for food, and cover long distances between food and water. They also developed tools and cooperation to do so, leading to bigger brains—and because the savannah was hot, they lost their hair.

Writer Elaine Morgan became interested in evolution in the 1970s. When she read books on the savannah hypothesis, she became skeptical that only male humans would spur evolutionary adaptation. Morgan wrote a non-scientific book called The Descent of Woman in 1972 which refuted the savannah hypothesis. She simply argued that humans would not have walked upright in order to cover distances faster, as most things that walk on four legs can outrun us. There also aren’t any other hairless animals in the savannah, debunking the idea that we lost our hair because of the heat. 

Morgan came across the work of marine biologist Alister Hardy, who proposed a theory called the “aquatic ape” hypothesis, suggesting that a band of woodland apes became isolated on an island and adapted to the water. He noted that like marine animals, humans have no hair, and we have fat attached to our skin (unlike other land mammals). He proposed the only reason for humans to share these traits with hippos, sea lions, and whales would have been “an aquatic or semiaquatic past.”

Very few people took Hardy seriously until Elaine Morgan, who built a compelling case on top of his theory. She theorized that for a long time, our prehuman ancestors spent time in and around the water, which helped them survive both on land and water. The water helped them evolve toward bipedalism, as standing upright enabled them to swim farther out and still breathe, and the water helped to support their upper bodies. It explains why we lost our fur, why we have fat, and why we have down-facing nostrils, which allowed us to dive.

Moalem returns to the idea of birth, to add his own contribution to the aquatic ape hypothesis. He examines water births, noting that for a long time, people believed water birthing was dangerous, with risks of infection and drowning. But according to an Italian study published in 2005, there is no increase in the rate of infection in mothers or newborns. 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.

Additionally, first-time mothers delivering in water have much shorter first stages of labor and need fewer episiotomies. The process may also be less painful: only 5 percent of women asked for an epidural in water births, compared to 66 percent of women giving birth conventionally. These results offer another suggestion that the aquatic ape theory might be correct, particularly because babies reflexively hold their breath and make movements that propel them through the water—a surprising instinct for an animal if it did not evolve around the water.

Moalem explains that his book is all about questions: the first being “Why?” and the second being “What can we do with that?” Moalem suggests that this curiosity has already led us to develop new ways to combat infection by limiting bacterial access to iron, or to open up new avenues of research through animals like the wood frog, or help us put pressure on infectious agents to evolve away from virulence. He explains that if we don’t ask questions, we’ll never find out what we could have discovered.