Shortly before his death in 1882, Charles Darwin received a letter from a physician and classicist named William Ogle. It contained Ogle’s recent translation of Aristotle’s The Parts of Animals and a brief letter in which he confessed to feeling “some self-importance in thus being a kind of formal introducer of the father of naturalists to his great modern successor.”
Aristotle is not typically remembered as the father of naturalists, but Darwin acknowledged a line of intellectual descent. “I had not the most remote notion of what a wonderful man he was,” Darwin wrote of Aristotle in his reply to Ogle. “Linnaeus and Cuvier have been my two gods, though in very different ways, but they were mere school-boys to old Aristotle.”
A fascinating new book by the evolutionary biologist and science writer Armand Marie Leroi claims that Aristotle fully deserves Darwin’s high praise. In The Lagoon: How Aristotle Invented Science, Leroi argues that Aristotle developed many of the empirical and analytical methods that still define scientific inquiry.
An immediate problem for anyone trying to present Aristotle as a scientist is that he holds beliefs like this: too much sex causes sunken eyes because semen drains matter from the human brain. Or this: the right-hand side of the body is more honorable and therefore hotter than the left. There is also his conviction that the human heart processes and integrates sensations from the external world. The brain, beyond storing the matter that becomes semen, was just a cooling device for when the heart’s fires blazed too hot.
Some of his observations about animals appear equally bizarre. He reports that the European bison fires caustic dung when pursued and that the trunk of an elephant is in fact a snorkeling device that allows it to swim. He even claims that hen partridges conceive just by smelling the scent of males.
Mingled with all the bizarre zoology, however, are many impressively accurate and detailed descriptions. His accounts of the hyena’s genitals, the parental behavior of male catfish, and the limited sensory capacities of sea sponges are just a few of the many things about which he was essentially correct.
Aristotle’s biological works mention roughly 500 different kinds of animals, and he gives such precise descriptions of internal anatomy that he probably dissected at least 35 of these. Lists of the errors and accuracies in his treatises can be multiplied nearly indefinitely, but a meaningful assessment demands more than a simple tallying of what he got right and wrong. Aristotle’s methods of analysis are the ultimate basis of Leroi’s claim that he invented science, and even when those methods generated results that are fanciful, eccentric, and simply wrong, their power is undeniable.
A fundamental technique of his scientific process was the collection of vast amounts of data. He interviewed hunters, travelers, fishermen, and farmers to get detailed information about the habits, structures, and environments of hundreds of animals. Some scholars think he may have even dissected an elephant that his former student Alexander the Great sent to Greece from India while he was off conquering the world.
Today, collecting data is taken for granted as a necessary part of scientific inquiry. But Aristotle’s empirical emphasis was revolutionary for the fourth century BCE. He was a student of Plato, a thinker more interested in the abstractions of mathematics and metaphysics than the myriad details of the perceptible world. The cause of flatulence in elephants, for instance, was just not the type of question Plato pursued.
Aristotle, however, had an insatiable appetite for data on the vast variety of features, behaviors, and structures of biological life. He learned that near the Black Sea rams don’t have horns, while in Libya there’s a sheep with long horns. He notes that on Naxos sheep have very large gallbladders, but on Euboea they do not.
While other authors in antiquity would simply repeat the myths and legends travelers brought back from distant regions (Herodotus on flying serpents comes to mind), Aristotle sought to verify reports whenever possible by observing phenomena for himself, dissecting animals, and interviewing people whose daily work brought them into close contact with the creatures he was studying. He even examined an aborted human fetus. Not only did he recognize the importance of gathering large sets of data, he also tried to monitor its quality.
But he was more than an encyclopedist. He collected such comprehensive data in order to analyze and interpret it. His theories and interpretations are often astonishingly insightful. One 20th-century Nobel laureate suggested that Aristotle deserved to receive the prize posthumously for his realization that the information that dictates and replicates an organism’s structure is stored in its semen. In some sense he was anticipating the discovery of DNA. His theory of inheritance can also account for recessive traits that skip generations, the contributions of both parents to the features of a child, and unexpected variations in traits that do not derive from either parent.
Many of his observations are readily recognizable to a reader of Darwin. He notes that an elephant’s size confers protection from predators and that fish with high rates of infant mortality produce a larger number of offspring to compensate for the likelihood that most of the progeny will perish. He showed a nuanced understanding of how the forms and features of animals are adapted to their environments. Darwin even mentions Aristotle as a forerunner who anticipates the theory of natural selection in the preface to the third edition of On the Origin of Species.
Aristotle perceived some of the universal associations between longevity, period of gestation, adult body size, and degree of embryonic development that biologists still study today. He noticed the correlations among these features, but he was sensitive to the distinction between correlation and causation and sought to eliminate confounding variables. Then he integrated his findings into broader theories with deep explanatory power.
Take his claim that “what nature takes from one party gives to another.” Essentially he is arguing that there are functional trade-offs in developmental biology. Growth in one body part often affects size and structure of other body parts. Darwin called the same phenomenon the “correlation of growth” and geneticist today study what they call “pleiotropic effects.” But the ideas are all fundamentally related.
Taxonomy was another major area in which Aristotle influenced the history of science. He considered the difficulties of placing certain animals—like the ostrich—within rigid classification schemes, and he recognized the subtle and blurred gradations that often separate different kinds of animals. But he ultimately arrived at the same principle of nested hierarchies that defined Linnaeus’ methodology. The genus-species distinction that we still use is a legacy of Aristotle.
Leroi is a brilliant guide to the history of science. He traces the history of ideas with skill and care, and he avoids the smug certainty of many contemporary science writers. This makes a certain sense given his deep knowledge of the theories of previous scientists. Studying the history of science is a necessarily humbling process; the countless blunders, dead-ends, and mistakes of earlier scientists are an invitation to reflect on how woefully flawed many aspects of our contemporary theories will appear after a few hundred or thousand years.
This is not to say that progress is impossible and each generation only makes different types of errors equidistant from the truth. Aristotle did make progress beyond earlier philosophers, just as Darwin advanced beyond Linnaeus and Cuvier. A careful reading of Leroi’s footnotes suggests that Aristotle may still have contributions to make. The Historia animalium contains around 9000 empirical claims; many are true, many are false, but some have yet to be tested.
It was only fairly recently that two of Aristotle’s seemingly bizarre claims were actually confirmed. Marine biologists have found that that while dolphins may not snore, they do vocalize in their sleep. And elephants do occasionally use their trunks as snorkels while swimming. Mercifully, studies have yet to confirm that semen comes from the brain.