Chapter 10: Are We Still Evolving? A Tale of Genes, Altitude, and Earwax
Like the chapter title hints at, this chapter is all about why we are definitely still evolving. She reminds us that humans undergo evolution just as much as any other species (possibly even more because there are so many of us in such different environments) and the idea that we are no longer evolving or have reached the pinnacle of evolution is ludicrous. Evolution has no goal and there is no stopping point for evolution. Our environments are always changing and there are always new diseases that are out to kill us (Coronavirus!).
The first example she uses is the from a study done by Emmanuel Milot who reviewed church records of women married between 1799 and 1940 on an island north of Quebec City. He noticed that the first age of reproduction of these women decreased from 26 to 22. He also noticed that the average number of children went from 3 to 4 meaning that women were starting to have more children as their window of fertility was growing.
Another example she used was people living in high altitudes such as Tibet and the Andes and how they have evolved to combat altitude sickness. The normal human response to low oxygen levels is to increase hemoglobin levels, but in the population studied in Tibet these people had normal hemoglobin levels and instead slightly increased their natural breathing rates. A group of researchers isolated a gene, HIF-alpha (hypoxia-inducible factor alpha) that was responsible for lower levels of hemoglobin in the blood of Tibetans, which helped reduce the increased number of RBCs, which cause altitude sickness. This is evidence of another amazing evolutionary event for humans, which if predicted correctly by geneticists could have only happened in the past 3,000 years.
Overall, Zuk finishes her book with the idea that we should “relinquish our paleofantasies.” What she means by this is that we need to stop fantasizing the past, hunter-gatherer lifestyle, and realize that we have changed a lot since then. We aren’t completely suited to our new environment, but also no species has ever been or ever will be perfectly suited to their environment. There is no optimal human way of life and we need to appreciate the differences between us to continue learning about our evolving genomes, which will help us appreciate living in the moment.
Chapter 9: Paleofantasy, in Sickness and in Health
Dr. Zuk starts off this chapter with the assertion that all of the reasons why people are trying to emulate our hunter-gatherer ancestors are because they are trying to live healthier lives. I agree with this sentiment and think the same of myself as I workout and eat healthy because I want to stay healthy and live a long, healthy life. There are many diets and lifestyles that promote that following them will protect one from certain diseases, but Dr. Zuk isn’t necessarily convinced of this argument. Instead she looks at our genes and evolutionary past to give us insight into the complex relationship we have with diseases. She agrees that many infectious diseases caused by bacteria, viruses, and parasites originally were transferred to humans by intensive farming as these animals were kept in large quantities and close quarters with humans. Although she agrees with this sentiment she also poses the idea that everyone dies of something and it’s hard to tell how long these diseases have been prevalent in humans. Humans have always been susceptible to disease and many of our genes originate from bacteria, so that the idea of disease being an advent of agriculture is a bit far fetched.
She also introduces an interesting viewpoint about genes and their incredibly long battle against infectious agents. She uses the example of AIDS to make the point that although there are new diseases, our genes are also evolving to counteract the virulence of these diseases. We have recently discovered the gene, CCR5-delta, which codes for a protein on T cells that prevents HIV from infecting the T cells. A group of scientists from the National Cancer Institute surveyed a thousands of people from different ethnic groups and used mathematical modeling to pinpoint that the gene originated about 700 years ago. This gene also was selected for, which means it had a legitimate affect on increasing fitness. It is theorized that this gene helped young kids survive smallpox, which is why it was able to increase fitness as smallpox killed children at a young age. Although CCR5-delta is a promising gene, it has its tradeoffs as research has shown that although it confirms immunity to HIV, it increases the likelihood of severe West Nile virus symptoms. Dr. Zuk uses this example to show that although gene evolutions are promising in fighting diseases there is always a tradeoff that comes about with adaptations.
Next, Dr. Zuk questions the widely-held idea that cancer is a modern illness. Cancer is supposed to be a recent phenomenon as it is due to increased technology radiation, poor diets, and other carcinogens. These all hold weight, but Dr. Zuk believes the increase in cancer diagnoses is not necessarily because the disease is more prevalent, but because our technology has gotten better at detecting it. Similar with COVID-19, originally our testing capabilities were so poor that the confirmed cases number was so low. Yet, recently with the increased capabilities of antibody tests we have seen that the actual infection rate might be much higher than we once thought. Much of the thinking behind cancer is a modern-day ailment is that remains (bones) of older humans don’t show any signs of cancer. This isn’t necessarily definitive, however, as most of the time cancer doesn’t metastasize to the bones before it kills the patient. Dr. Zuk cites Tony Waldron’s research in 1996 where he analyzed records from the early 1900’s (before smoking was prevalent) and then burials in the 17-1800’s. He then used current day statistics to predict the prevalence of certain types of cancers and how they would present on ancient skeletons. What he surprisingly found was the rates were the same nowadays as they were hundreds of years ago. This suggests that there were many natural carcinogens that caused cancer in the past, and one of these could be infectious disease. Dr. Zuk uses this sentiment to propose that it is human nature to be vulnerable to all types of diseases and it is impossible to prevent senescence. Many of our genes that could increase fitness may in the future increase susceptibility to disease, which is what she calls negative pleiotropy. These genes continue to be passed on because they increase fitness so they are passed on before the negative part of the gene ever takes place.
Chapter 8: The Paleofantasy Family
This chapter is focused on the uniqueness of the human baby and why it is so different than any other species’ young. Our babies are much less independent than any other primate infant and need much more care and coddling from the mother. Dr. Zuk is a strong supporter of the OB theory in that because of our bipedalism and larger brains babies are born prematurely and thus our brains develop largely outside the womb. Zuk holds the view that because of this human beings were the ones who invented the idea of childhood, and in some ways adolescence, as almost all other babies are born able to function, reach sexual maturity, and reproduce much faster than humans. It was interesting to read the Dunsworth 2018 article on EGG because in it she explicit quotes Dr. Zuk as a proponent of OB theory in Paleofantasy, so as I was reading both points of view it was very interesting to see two sources that I was currently reading disagree in such a way.
Next, the author points out another anomaly with human babies in that usually the baby has multiple caregivers besides its mother. With other primates, it is very rare to see a baby interact with anyone besides its mother. With humans, although they have very strong connections with their mother, they also have other relationships. This is a unique trait to humans and is deemed alloparenting. She hypothesizes that this is the case because it allows human babies to wean off their mother’s milk earlier, and although they still need a lot of care, it’s not all on the mother so she can get pregnant again quicker. This is the reason why we are able to have so many siblings so close in age. The term for this is called cooperative breeding, which is the idea that the whole family helps raise the infant instead of just the mother. An example of another animal that does this is meerkats where the whole troop helps take care of the young as there is only one couple that breeds.
Another interesting topic she brings up is the field of evolutionary pediatrics. She uses Dr. James Mckenna’s research from Notre Dame to show that many of the Western practices of childcare is against our nature. He says that children still need to be taken care of the same way they have been for millions of years. This includes almost constant contact with their mother, especially when sleeping as well as tending to them whenever they cry. He believes that babies have evolved to sleep in social environments, so we should adhere to their nature and give them as much attention as possible.
Chapter 7: Paleofantasy Love
This chapter addresses the questions of are humans supposed to be monogamous and what are the origins of our gender roles? She first looks at Darwin’s idea of sexual selection and how this leads to differences in sexes. She uses the examples of peacocks and how male peacocks are brightly colored to attract their unimpressive-looking female mates. She also uses the example of male deer having impressive antlers to attract females and the brawn of male gorillas to outcompete each other for female attention. Female opinion is what drives this selection because they have a lower base level of output (a definite number of eggs vs indefinite amount of eggs to fertilize for males). Females also will be best served passing on their genes with the most fit male partner. These are the reasons why females guide sexual selection and choose the most fit males. The author, however, does make a distinction that just because of the higher cost of reproduction doesn’t mean females don’t enjoy sex as much as males and pushes back on this idea as she states that many biologists who think this have their own biases.
To address the question of monogamy the author first looks at our primate ancestors, chimps and bonobos. Chimps and bonobos were first used as models for how early hominins reproduced, but that idea has started to come under fire by many anthropologists as their relations are much more violent and are so far removed from modern humans that it is not valid to compare. Human mating patterns have greatly evolved since we split with bonobos over 5 million years ago and their relations have greatly changed as well. To answer the question of monogamy, she admits that although monogamy is by far the most common human practice, there are still many cultures that practice polygyny. There is also evidence from linguistics studies that show that very early hunter-gatherer ancestors had evidence of monogamy meaning that it isn’t an industrialized invention. A different gene study about the female X chromosome shows that there is also evidence of polygyny in our ancestral past, so both types of relationships were practiced. Zuk concluded her analysis that there is no one true pattern of sex for humans and both practices have been present and worked historically.
Zuk also touches on the idea of gender roles in a hunter-gatherer society. She challenges the theory of a sex contract that men go out to hunt, bring home food, and the female stays faithful to that male who takes care of her. However, many female anthropologists, including Adrienne Zihlman From UC Santa Cruz and Rebecca Bliege Bird of Stanford have come up with a different hypothesis that males and females relied on females to gather consistent, smaller batches of plants, etc. as they were more reliable and consistent than hunting. This constant supply of food allowed a husband to be able to hunt. She concludes the chapter with the refutation of the sexual contract idea as it would’ve been impossible for this relationship to last in the ancient world.
Chapter 6: Exercising the Paleofantasy
Next, the author tackles the idea of exercising like an ancient human, and explains that “new age cavemen” are taking up CrossFit to emulate ancient exercise. CrossFit is based on random, short, high intensity lifts and movements that are supposed to mimic ancient conditions and practices. She cites many other authors who support the idea that we should be exercising like a hunter-gatherer and modern-day equivalents to ancient practices like instead of gathering plants we should weed the garden or instead of butchering a large animal we should split wood with an axe. Although she pokes some fun at these somewhat ridiculous practices, she does agree that incorporating movement and activity in our lives are integral to our health and wellbeing.
The author then talks about the idea of an “Active Couch Potato”. The active couch potato is someone who works out vigorously for a short period of time and then sits on the couch the rest of the day. She concludes that according to an Australian study, just a one-hour increase in sitting down and watching TV increased the risk of mortality by cardiovascular disease by 18%. She recommends following James Levine’s model of NEAT (non-exercise activity thermogenesis), basically meaning that on top of us working out we should be expending energy doing basic household things like using the stairs, mowing the lawn, walking out dogs, etc. These small outbursts of energy add up and help us burn calories. She then continues along with Levine’s argument in that some people are programmed to be NEAT conservers (people who don’t move around much when food i scarce) and NEAT activators (increased activity when food is scare to get more food). These both would have been beneficial when food had to be worked for, but now that food is always plentiful NEAT conservers have started to put on weight as they don’t move around as much as they should. This trend is the reason for the obesity epidemic in this country.
Zuk then tackles the idea of persistence hunting and barefoot running. This idea is that humans evolved to become bipedal and then run long distances. This ability to run long distances then enabled humans to hunt down other animals by inducing heat stroke as we had better thermoregulation, and this introduction of meat to our diet was the catalyst for our brain growth. I first heard about this idea through Christopher McDougall’s book Born to Run, (one of my favorite books to this day) in high school, and Zuk also references the book, so I found this discussion especially interesting. She explains the Endurance Running Hypothesis and includes the idea that humans don’t have an optimal running speed as they have the same efficient stride at all speeds. She also mentions the idea that humans originally ran barefoot, which meant that they had a different gait and strike point when comparing running with a running shoe (forefoot vs heel). This allowed us to prevent injury and better use our anatomical foot arch as a spring. Zuk cites many studies that push back against the Endurance Running Hypothesis that include ideas that the environment was too dense, ancient humans weren’t smart enough to track animals, there is no evidence of a single optimal running speed, we would expend too much energy to make it worthwhile, etc. She concludes the argument with a compromise that endurance running probably shouldn’t be as evangelized as it is by McDougall, but there is definitely some merit to this and ancient humans were far better runners than most of us are today.
Lastly, she cites studies that have isolated the gene ACTN3 as a potential gene responsible for production of a protein that is involved in fast-twitch muscle fibers, basically a gene that could make one more athletic. Although this gene cannot predict whether or not someone will be a great athlete or not, it is proven that it increases fast-twitch muscle capabilities and is present in many power/speed athletes.
Chapter 5: The Perfect Paleofantasy Diet: Meat, Grains, and Cooking
This chapter is focused at rebutting the idea that the paleo diet is the optimal diet for modern human beings because it is what our ancestors ate thousands of years ago. One pillar of the paleo diet is not consuming grains because grains only came about with agriculture. The paleo diet is centered around meat, fruits, and vegetables. Dr. Zuk then takes the remainder of the chapter to explain why the paleo diet is inaccurate in emulating what our hunter-gatherer ancestors ate.
She pulls evidence from Anna Revedin of the Italian Institute of Prehistory and Early History in Florence that on the grinding stones of 30,000 year old archaeological sites they found bits of starch grains. They used this evidence to conclude that our ancestors made flour and thus made a type of bread. She also references findings by anthropologist Amanda Henry of plaque of Neanderthals that showed gelatinized starch grains, which is evidence of the starches being cooked. This is evidence that ancient humans ate and processed grains, which would prove the paleo diet inaccurate. She also includes a study done by the U.S. News & World Report, 20 different diets were evaluated by scientists, nutritionists, and physicians. The paleo diet comes in dead last in regards of weight loss, nutritional completeness, safety, and prevention of diabetes.
She also challenges the notion that ancient humans were ravenous meat-eaters who relied heavily on hunting meat and gathering fruits and vegetables. She noticed that instead anthropologist Frank Marlowe’s data shows that the ancient human’s diet varied largely and was based on the environment they lived in. Plants were the largest source of food for our diets and meat was more of a nice-to-have. She also brings up the fact that our current food supply has been modified drastically from the wild forms of many of our meats, vegetables, and fruits. She cites comparisons of 4 oz of wild deer meat having 2.2 grams of fat while store-bought extra-lean ground beef has about 18.5 grams of fat for the same portion. This is another issue with the paleo diet as someone who truly wants to eat meat as our ancestors did will not be able to find that type of meat at a grocery store. Overall, Zuk concludes that if one wants to eat like our ancestors there isn’t really a specific diet that is universal among hunter-gatherers. There is no such thing as a natural diet for humans as we all have eaten widely different types of foods and these foods have changed our genes and microbiome to prefer different things.
Chapter 4: The Perfect Paleofantasy Diet: Milk
In this chapter Dr. Zuk shifts the argument of rapid evolution away from other animals and towards humans. She uses the human practice of consuming milk and dairy as her casestudy on rapid human evolution. She introduces the conflicting opinion that it is unnatural to consume cattle’s milk as it was not intended for human consumption and it causes disease in humans. She then describes why humans drink cow’s milk as it has the same amount of calories as human milk, just more protein and less fat. The problem with digesting milk is that all types of milk contains the lactose sugar. Lactase, the enzyme that breaks down lactose, is present in all mammals at birth. However, what makes it a point of contention is that in almost all mammals (humans included) lactase production stops before adulthood. The inability to break down lactose is called lactose-intolerance, and although all other mammals become lactose intolerant, many humans are still able to break down lactose far into adulthood.
Previously it was assumed that lactose-intolerance was rare and not the norm, but recent surveys have showed that only 35 percent of the world’s population exhibits lactase persistence. Dr. Zuk now asks the question why is this the case and how come people who show lactase persistence are clustered in certain areas of the world? She looked at new genomic and archaeological data that showed the ability to drink milk evolved as it was a rich source of protein and nutrients in some places and as hydration in other places where water wasn’t as readily available. The most fascinating part of her research was that lactase persistence co-evolved in these different populations in as short as 7,000 years. This proved her point that evolution takes a lot shorter than we once thought and the idea that we are stuck in our genes is not necessarily accurate.
Chapter 3: Crickets, Sparrows, and Darwins — or, Evolution before our eyes
The goal of this chapter is to prove Zuk’s point that we aren’t stuck in our evolutionary past and that evolution happens quicker than one might think. We have always been told the notion that it takes thousands or millions of years for evolution to occur. Zuk uses examples of other (non-microbial) species that have evolved in incredibly short periods of time.
She first gives an example of a certain species of cricket that lives in Australia and many islands of the Pacific such as Tahiti, Samoa, and most recently Hawaii. Male crickets call to attract females to mate. However, specifically on Hawaii there are parasitic flies that can also hear the crickets chirps. This is dangerous for the male crickets because the female flies are also attracted to the crickets, but for another reason. They lay their larvae on the crickets, which then burrow into the cricket and develop inside the cricket’s body, eventually killing it. She noticed a decreasing cricket population every year she returned to the island until 2001 she only heard a single cricket calling in their usual field site. She then returned in 2003 and the cricket field was silent. However, when she looked closer the field was teaming with crickets hopping around and the area had more crickets than she had ever seen before. After doing more research she realized that the majority of crickets now exhibited an adaptation to their wings that prevented them from being able to make the chirping noise to attract mates. This type of evolution happened in a mere 5 years.
Zuk also uses more well-known examples of Bumpus’ sparrows size changing drastically after one large storm, Darwin’s finches, Reznick’s guppies, Australian cane toads, and other species that evolve in an incredibly small period of time. She uses all these examples to exhibit her idea that evolution can actually happen in a much shorter timespan than we once thought given the correct conditions. She also looks to the future that with increasing climate change, environments will be changing and many species will have to either undergo rapid evolution to survive or risk being wiped out.
Chapter 2: Are We Stuck?
In this chapter, Zuk tackles the question of agriculture and the pros and cons to whether it was an overall good or bad to humanity. She acknowledges the claims made by paleo-enthusiasts as well as prominent historians/anthropologists as to agriculture being cause of many of the illnesses that plague our society. She describes the argument that humans have been around for tens of thousands of years, but farming has only been around for a mere fraction of the time. She then transitions to the overall argument that human farming then led to technology, which led to an incredible change of lifestyle that happened at an astounding rate to which our bodies were unable to evolutionarily keep up. Hence, the name of the chapter, she is addressing the notion that the human body is evolutionarily stuck in an ancient mode.
She first brings up Jared Diamond’s famous argument of agriculture being, “The Worst Mistake in the History of the Human Race.” He argues that agriculture is the reason for many of our chronic and infectious diseases, social and sexual inequality, and overall climate change. She also quotes Spencer Wells (National Geographic Society) who states that agriculture is what created civilization, and that agriculture is unsustainable on the planet. To push back on these arguments she distinguishes 3 different types of agriculture: horticulture, pastoralism, and intensive agriculture. Horticulture is simple and includes using primitive tools to dig holes to plant very small-scale wild plants. Pastoralism is keeping herds of partially domesticated animals and letting them graze on wild patches of foliage. Intensive agriculture is what we consider as farming and raising animals for slaughter. She posits that agriculture has actually been around for much longer than we have thought in smaller scales and other forms. She argues that these types of agriculture are not harmful to the planet, but acknowledges the impacts of intensive agriculture. She agrees that this type of agriculture can eventually lead to stratification of society with the division of labor and that agriculture did shift the human diet to more rely on grains like rice and wheat causing carbohydrates to become a more readily available source of energy.
She argues back against the idea that agriculture is evil and that we should all switch to the Paleo diet with evidence that Neanderthals and early modern humans did occasionally eat grains and rely on thinks like roots and tubers. She also argues that modern-day hunter-gatherers spend lots of time and energy on hunter-gathering and that it is not so easy to rely on that type of food sourcing. Although there was evidence of some malnutrition in skeletons from early agricultural societies from relying on one crop, that is no longer the case as humans have access to most types of foods.
She acknowledges that the prevalence of carbohydrates and sugars in our modern society is detrimental to our health, but says that complaining that we aren’t adapted to eating these types of foods is a shortcut and an excuse. She concludes that humans need to acknowledge and realize which types of foods we are “mismatched” eating and change our behaviors, but states that this doesn’t mean we are stuck in an evolutionary past.
Although I agree with her that agriculture is not the nature of all evils that plague society, I’m not sure if she defended the argument that she presented to defend very well. She proposed that people like Jared Diamond blame agriculture for obesity, infectious disease, social inequality, and climate change, but instead of directly disagreeing with him she tries to just explain different types of farming. I understand where she is coming from as not all types of farming are bad and it is sustainable, but I do wish this was more clear and not necessarily an attempt at a complete rebuttal.
Chapter 1: Cavemen in Condos
Dr. Zuk starts off her book referencing a New York Times article that talks about people following an ancient, paleo lifestyle while living in New York City. Their practices include bursts of exercising the mimic escaping predators, strictly carnivorous diet, and frequent blood donations to simulate being wounded on a hunt. She references many online forums of people who participate in this lifestyle and addresses the popular sentiment that agriculture is one of the most important reasons for why humans went away from the hunter-gatherer lifestyle and is at fault for many of our current chronic diseases. She uses these somewhat outlandish practices and claims to then posit her overall question for the whole book as: “…if we want to go back to a healthier way of life, what exactly should we emulate? How did those ancestors live anyway, and where do we get our ideas about early humans?”
The next part of the chapter is a brief overview of the evolutionary history of modern humans starting with Hominids splitting from nonhuman primates and covering Ardipithecus, the various types of Australopithecus, and then the various species of the genus Homo, including Neanderthals. She makes the point of saying that there is no definite lineage of Homo sapiens.
She then inquires about ancient, hunter-gatherer societies, and ponders the question about how do we know what their life was like? She presents evidence comes from fossils of ancient hominins, modern-day hunter-gatherers, and modern apes. She says that many of our notions about the Paleolithic area are from these techniques, but almost all of the scientific evidence she uses to debunk certain “paleofantasies” come from genomic data.
She then ends the chapter after describing some of the practices of modern-day hunter-gatherers, like the Kalahari Bushmen or Hadza nomads of Tanzania, with the notion that there is no clear-cut paleo-lifestyle and that we know a lot less than we think we do.