60 pages • 2 hours read
Eve: How the Female Body Drove 200 Million Years of Human Evolution
A modern alternative to SparkNotes and CliffsNotes, SuperSummary offers high-quality Study Guides with detailed chapter summaries and analysis of major themes, characters, and more.
Chapters 2-3Chapter Summaries & Analyses
Chapter 2 Summary: “Womb”
Bohannon describes the ecological apocalypse, Chicxulub, that occurred about 66 million years ago, likely following an asteroid, in which nearly all the creatures except the small ones died. One such survivor was a rat-like creature called Protungulatum donnae, or “Donna,” who gave female humans the evolutionary trait of the placenta. Though Morgie and her near descendants laid eggs, before Chicxulub, her descendants started growing their babies inside their bodies, becoming either marsupials, which have pouches, or eutherians, which have a placenta (73). Bohannon explains that despite the taxing and dangerous nature of pregnancy and childbirth, pregnancy regulates the embryo’s temperature, keeps it safe from predators, and allows the mother to look farther for food. She then says that the uterus, ovaries, and fallopian tubes are remnants from when mammals used to lay eggs. The evolution of the placenta started following Morgie’s time with the development of monotremes, which have a single cloaca; marsupials, which have two holes; and placentals, which have three holes. Placentals needed to evolve to protect their babies from bacteria, with monotremes like the platypus producing eggs with an anti-bacterial fold in their cloaca. However, eggs can still be exposed to urinary and fecal germs when they are laid. Marsupials and eutherians, which have multiple holes, can avoid this. Human embryos usually start with a cloaca and then, through gestation, develop rectums and later genitalia. Urogenital birth defects often betray humans’ evolutionary pasts with cloaca and multiple cervixes, uteri, or vaginas. The eutherian body plan allowed human Eves to more safely give birth to larger-headed babies. However, childbirth can still cause problems such as bladder prolapse, especially after hominins started standing and walking upright. Female humans’ straightforward reproductive system also made the act of intercourse simpler than for animals such as rhinos.
In tracing the origins of the placental womb, paleontologists and biologists found the Eve of placental wombs in Donna. Donna, unlike Morgie, had a bowl-shaped pelvis and a single uterus and vagina. Bohannon states that abnormalities such as female humans who are born without uteruses are glitches in the human reproductive code that sometimes show humans’ evolutionary past. She theorizes that human evolution creates these abnormalities to provide nonreproducing humans who will help care for other human young. She uses the infertile female worker ants and bees as examples, which will help care for the colony’s and hive’s young, respectively. Bohannon also hypothesizes that attraction to members of the same sex likely exists for this reason as well. Bohannon says that she believes Donna was a sexual creature whose uterus created babies who would later lead to the formation of humanity, as her uterus is like ours. As her descendants grew bigger, their uteruses also grew bigger. She then explains that as our ancestors grew larger and their babies grew larger, they produced fewer of them to preserve the mothers’ health and because they had fewer predators.
Bohannon then explains that menstruation is something few mammals do, which is remarkable. She remembers learning about menstruation from an undertrained and underinformed teacher, who told her that menstruation was the female body’s way of preparing for a baby and a punishment for not having enough pregnancies. She notes that this is a common belief even in scientific fields. Bohannon also states that the idea that menstruation and lack of pregnancy are negative is a pervasive one. She then says that some scientists believe menstruation was meant to indicate a lack of fertility and reduce sex but debunks this by showing that people will often have sex regardless of whether a female person is ovulating, menstruating, pregnant, or breastfeeding. She states that menstruation in Donna’s descendants was rare and did not appear until her descendants became higher primates. Bohannon concludes that menstruation is part of how female individuals survive their turbulent reproductive systems and that in reproduction, the mother and fetus are constantly at war, with both sides unable to win or lose until childbirth. Bohannon challenges the idea that pregnancy is inherently positive, with common conditions like preeclampsia and post-birth problems and diseases like malaria putting pregnant people in danger. She thus concludes that even with modern medicine, it is healthiest for people to not get pregnant at all. To get to the point where female individuals could make their reproductive choices, however, Donna’s descendants needed to develop larger brains and become primates.
Chapter 3 Summary: “Perception”
Bohannon recalls working as a model for an art school when she was younger and noticing that early in her job, the male artists drew her breasts much larger than they were before progressively drawing them more realistically. She wonders if male and female individuals truly perceive the world differently. Bohannon then briefly calls back to the asteroid mentioned in the previous chapter before describing the eruption of Mount St. Helens in 1980, with the volcano causing great destruction to the flora and fauna around it before it quickly recovered. She says that the recovery after Chicxulub was much slower and required the development of new organisms. One such organism was Purgatorius—or “Purgi,” the Eve of perception. Purgi, who first appeared about 66 million years ago, was the first primate and, unlike Morgie and Donna, was an omnivore. Living in the trees, Purgi and her descendants needed to be able to see which fruits were good to eat and hear their children.
Bohannon describes the noise and chaos of tropical rainforests and how, in the cacophony, the Eves of perception needed to distinguish important and unimportant sounds. Primates evolved to hear and make lower and higher pitches to make themselves heard through clutter. Through this evolution, they began to form a system of complex communication. Male and female primates evolved differently in this way, with female primates needing to perceive wider varieties of sounds. Bohannon recalls when her friend’s small boy was two. She remembered not being used to children and thinking she would get used to it, but after having her son, she was highly aware of his cries. She explains that studies have shown that male individuals are more adept at hearing lower pitches and that female individuals are more adept at hearing higher pitches, including babies’ cries. This is evolutionary, with mothers needing to be able to hear their children and act quickly to protect them from danger or feed them. Male individuals are also more likely to develop hearing loss, losing access to higher-pitched sounds first. Female individuals are more sensitive to loud noises, with Bohannon using an example of her then-boyfriend playing Fallout 4 loudly in 2015. This is affected by otoacoustic emissions in the cochlea, or OAEs. Male and female individuals have distinctive OAEs, though lesbian and bisexual women will often have OAEs more like male individuals, as do female individuals who have fraternal twin brothers.
Purgi also gave female individuals a more varied sense of smell than male individuals. Scents are important for mammals’ survival, hunting, and reproduction. Animal pheromones play an important role in reproduction, but humans and primates do not have them because they likely evolved to rely more on sight. Bohannon recalls a study in which people had androstadienone, or AND, a hormone found in male underarm sweat, placed on their upper lip. Cisgender heterosexual women, gay men, and transgender women had similar responses, but lesbian women did not. Bohannon then states that female individuals can better perceive faint scents, with the advantage lowering after menopause. Female senses of smell become even stronger during pregnancy. Pregnant people’s increased sensitivity also comes along with nausea, which Bohannon argues is beneficial because it can help pregnant people avoid dangerous toxins. This is also why female individuals are more sensitive to bitter-tasting foods, with bitter plants being more likely to be poisonous. This is another trait they inherit from Purgi, who needed to know which fruits were sweet and ripe. Sight is the other important sense in female perception’s evolution.
In their evolution, humans’ ancestors developed eyes in the front of their heads—a predator trait—rather than on the sides of their heads—a prey trait. Primates needed to change their diet as insects became better at hiding, forcing primates to need to see more of what is in front of them. Primates, especially females, also evolved to sleep earlier in the night until they became diurnal. This was especially important for female primates, with modern humans’ reproductive systems being affected by having a distorted circadian rhythm, such as female individuals who work night shifts. Another important reason is the evolution of color vision in primates. Mammals are mostly red-green colorblind, with red-green color vision developing first in proto-monkeys around 40 million years ago. Female individuals have especially strong red-green color vision, with male individuals being the vast majority of humans with red-green colorblindness. This is because Purgi and her female descendants needed to know which fruits were safe based on their color.
Bohannon concludes that the male artists did not initially draw her breasts bigger because of the male gaze or any sexism but because of a lack of realistic perception in relation to the rest of her body, noting the difficulty artists initially have in drawing foreheads. She then discusses female individuals who are tetrachromats, who see four wavelengths instead of three, like some bird species. There might be up to 12% of these individuals, according to Bohannon, but most will never be called to use it, and she says that they likely experience the world in the same way as other female individuals do.
Chapters 2-3 Analysis
Chapters 2 and 3 highlight further development of the female human body and its significance by showing how the formation of the uterus and the senses helped humans’ ancestors evolve, adapt, and survive. The Evolution and Historical Impact of the Female Body is evident in the development of the human womb and human perception, and this theme continues to serve as the core of Bohannon’s informative work.
In Chapter 2, the development of the uterus and of giving birth to live young shows how birthing mammals further evolved and how this evolution would eventually lead to the human species’ perseverance. The development of the uterus was a remarkable feat for mammals, one that has also been a double-edged sword. Bohannon explains that the evolution of most mammals into birthing species rather than egg-laying species has benefitted mammals because they “can spend more time looking for food in a wider area” and “don’t have to worry as much about keeping your eggs at a certain temperature” (74-75). Birthing mammals also can better protect their young from bacteria because they have two, three, or more separate orifices. This has helped protect mammalian species, including humans, from bacterial diseases. However, “[B]oth gestation and birth are far more taxing and dangerous” due to the impact of developing young inside the mother’s body (74).
Furthering the topic of female anatomical history impacting male anatomy, the author addresses how the formation of female mammalian ovaries, uteri, and separate holes led to male mammals evolving as well—for example, going from having a single cloaca to having two holes, including the urethra inside the penis. Mammal, including human, embryos similarly go through an evolution during gestation. Male and female embryos begin with a cloaca before developing multiple holes and an extensive reproductive system. Female fetuses develop ovaries, uteri, vaginas, and vulvas, including clitorises, along with rectums. Meanwhile, male fetuses develop penises, testicles, and rectums. The development of the womb has changed mammalian and human anatomy permanently and created reproductive plans that better allow for positive outcomes. Despite these changes, childbirth remains a dangerous endeavor for female humans, even with modern medicine.
Chapter 3 delves into the tuning of human senses, especially in female hominins, and how the evolution of humanity’s ancestors into primates led to the development of these strong senses. Chicxulub and its turbulent aftermath have made humanity’s ancestors, including Donna and Purgi, far more vulnerable than their ancestors. By Purgi’s time, this required her kind to develop into primates and become significantly more perceptive to the world around them. Bohannon shows how this impacts humans today, with their uteruses and reproductive systems being vulnerable and their senses highly astute, especially concerning their babies. The development of the human senses has also progressed human history. The newly primate hominins of Purgi’s age were tree dwellers who needed to be highly alert of predators and able to sense their children and protect or feed them. This has allowed humans, but especially female individuals, to develop keen senses of hearing, smell, and sight, with female individuals being able to hear higher pitches, smell fainter smells, and see multiple shades of color. Bohannon even believes that human senses, particularly female human senses, might not be done evolving in the modern age. Many people assigned female at birth are tetrachromats, meaning that, unlike most humans, they can see in four color dimensions instead of three. Up to 12% of people assigned female at birth might have this ability, and this trait is only found in humans and birds, which Bohannon finds promising and amazing, calling these female individuals “secret superheroes” with “eyes like birds” (160-61). Though she laments that most female individuals do not have this ability and that those who do might not be fully aware of it, this might be an evolutionary possibility for female individuals in the future.
The discussions of early childbirth and senses in female hominins is thematically in conversation with The Intersection of Science and Gender, which also plays an important role in this chapter group. The lack of study of female biology underserves those with female anatomy, limiting medicine and scientific advancements necessary to prolong the success of the species. Bohannon also, once again, rejects gender essentialism and the notion that people with sex abnormalities do not have a significant purpose in human evolution. In Chapter 3, she uses the studies with AND to compare and contrast cisgender heterosexual women’s response to the male pheromone with the responses of gay men, lesbian women, and transgender women. Gay men’s positive reception to the pheromone and lesbian women’s disinterest are established to show the audience that their sexual orientations are natural. The similar responses trans women had to cis heterosexual women highlights that trans people may have been born with sex organs associated with another sex, but their senses are much closer to that of the sex with which they identify. This was also seen in scientific studies of OAEs, which showed gay men having ones similar to heterosexual men and bisexual and lesbian women having more masculine OAEs than feminine. It also showed trans women with OAEs similar to those of cis heterosexual women. Though these studies do not tell the full story, they provide interesting insight into how senses differ not just by sex but also by sexual orientation and gender identity. These important findings regarding sex and gender are often disregarded in favor of the traditional, cis male norm in scientific study, which is more socially accepted and well established.
Bohannon continues to use imagery to connect with her readers, maintaining the accessible language and tone introduced in the first section. She uses descriptions of Donna and the aftermath of the Chicxulub to show that it was catastrophic and devastating for most of the world’s life and that Donna is a survivor. It is her persistence and adaptability that has allowed humanity to form. In Chapter 3, she uses visual and auditory imagery to make readers think about the noise and chaos of tropical rainforests and how important it was for our primate ancestors, such as Purgi, to develop strong senses and navigate the treacherous and vibrant atmosphere of the forests and jungles. This section, overall, moves along Bohannon’s trajectory introduced in the first section as she uncovers the numerous ways that Eves have influenced female anatomy today and why this is relevant in modern society.
Unlock all 60 pages of this Study GuidePlus, gain access to 8,800+ more expert-written Study Guides.
Including features:
Featured Collections
Anthropology
View Collection
Books that Feature the Theme of...
View Collection
Books that Feature the Theme of...
View Collection
Family
View Collection
Feminist Reads
View Collection
Health & Medicine
View Collection
Nature Versus Nurture
View Collection
Science & Nature
View Collection
The Past
View Collection
Women's Studies
View Collection