Humans have wanted to understand our bodies the entire time we’ve had them, which is to say, the entire time. Late Classical Athens, around 300 BC, at a peak of intellectual prosperity: Herophilos cuts into a corpse. From this, he’s going to make the novel argument that the brain contains knowledge, and in doing so, he’s going to criticize Aristotle’s writing, which describes the brain as something akin to an air conditioner. Aristotle thought the brain was a cooling chamber, essentially, to prevent the heart from overheating, and that cognition happened in the heart. Much, much earlier, around 1000 BC in India, Sushruta, in his foundational surgical text, overestimated the bone count in humans by over 100. Many ancient societies had impressively detailed understanding of anatomy, considering they had no microscopes, no cameras, no X-rays; usually nothing more than their knives and eyeballs.

It’s important to note as well that this article is a brief overview of a complex subject, with a major focus on Classical, meaning Ancient Greek and Roman, examples, and is in no way a complete story of early anatomical developments across the globe. Asia, Africa, the Americas and the Arab world each had their own rich and complex traditions, beyond the few examples cherry-picked here. Most societies had a few impressive hits and a few impressive misses; in a way, their approach to science isn’t all that different from ours today. What can we learn from them, and what can we learn about ourselves?

In Ancient Athens, Aristotle believed the heart to be both the intellectual and emotional center of humans; the “seat of the soul” (1). Some remnants of this remain in our modern association between heart and emotion, though we know now it isn’t backed by science. His reasoning behind this was the convergence of blood vessels at the heart and its importance; from this, he also, perhaps reasonably, thought it to be the source of blood (2). Despite being deservedly considered a major anatomist, Aristotle likely made his observations from examining and dissecting the bodies of animals, particularly lower mammals, like dogs or livestock, instead of real humans (3). He unknowingly used homologous structures, long before evolution or even Charles Darwin himself was conceptualized, to essentially assume the anatomy of humans from other animals. Given this, his conclusions on the brain become a little more understandable. The brain is a strange-looking organ, critically important to life, though not obviously connected to the pulse or rich with blood; how were they to understand the structure of nerves and white matter? That it assists the heart in some way becomes a logical conclusion. So why not serve a cooling function? Blood is hot, so the heart must get hot. Overheating is usually bad; see fire. And the brain’s size makes it ideal for such a thing.

The thing about anatomy and science, Aristotle’s assertion being one primordial example of many around the ancient world, is that it changes. Herophilos and Erasistratus were two more Greek anatomists who succeeded and often contested Aristotle. Unlike him, they dissected humans, having no qualms about a man’s dead—or, according to some sources, still alive—body (4). However, they offered several accurate, or at least more accurate, insights inside human bodies. Herophilus argued that the brain wasn’t a cooling chamber but contained knowledge (5). While he was at it, he argued that the heart has four chambers, unlike Aristotle, who claimed it only has three (5). Many of Herophilos and Erasistratus’ insights required Aristotle’s, or some other prior Mediterranean scholar’s, claims to give them something to criticise.

Praxagoras was one such anatomist, from about 400 BC, about 100 years earlier. He correctly associated the pulse with natural movement within the body, but also asserted that arteries carry air (6). There is, possibly because of this claim, debate as to whether he had any practical anatomical experience or observed any dissections. If so, it’s quite impressive to miss the blood in arteries. He did, however, note that veins carry blood (2). Thus, he was later included in Herophilos’ critique. Before we criticise how long it took for them to realise seemingly obvious facts, we must remember that bloodletting as an acceptable treatment persisted into the 19^th Century. Modern and recent understandings are far from flawless. A couple of hundred years later, Galen, a Roman from the late 2^nd Century AD, would voice similar critiques (2).

Galen would later become famous for his theory of the four humors: blood, yellow bile, black bile, and phlegm, each with associated personalities and elements (7). While these are all real liquids found somewhere in the human body, they do not really work as the four-way counterbalance he describes. Galen made some incredible leaps forward in Roman anatomy, including developing more elaborate tools for dissection and surgery processes, which would be instrumental in allowing future developments in the field. However, he also learned more anatomy from treating severe gladiator injuries—which is awesome—or like Aristotle, from dissections and studies on lower mammals (7). This led to some interesting conclusions; his description and diagrams of a human uterus match that of a dog’s uterus exactly, for example (7). He did well with the tools he had, but guesswork has its limits.

Three hundred years before Aristotle, and over seven centuries before Galen, the ancient Indian physician Sushruta, a continent away, was revolutionizing, and if there was nothing to revolutionise, inventing surgeries and surgical techniques. He also valued an understanding of human anatomy, which likely contributed to his surgical skill, and dedicated a portion of his seminal Sanskrit work, Sushruta Samhita, to anatomy, calling it the Sharira Sthana. In his work, he describes in detail the head, which he correctly identified as the major center of essentially all function, particularly the cranial nerves (8). He also includes the first detailed guide to human dissection, alongside the anatomy of the embryo at various developmental stages; this is described as arising from seven skins, each with their own associated ailments, and while the skins are anomalous, many of the ailments correlate impressively with known diseases (8). 

There’s also, incredibly, a detailed description of cataract surgery procedure, where exceptionally specific incision locations in the cornea are interspersed with instructions to sedate the patient with wine mixed with cannabis, which makes sense in a world far predating modern anesthesia, then to spray the eye with breast milk (9). This part seems outlandish and harder to explain, but anyone who has studied immunology can tell you that breast milk contains antibodies and antibacterial proteins. Sushruta likely made some link between breast milk and reduced post-op infections, even if there were not yet microscopes to see bacteria with. Even if they couldn’t see why on the molecular scale, ancient anatomists were able to understand what worked and what didn’t and justify it to the best of their knowledge.

When Sushruta describes the bones of the human body, he does so in great detail, and also counts more than 300 of them. Humans typically have 206 bones, give or take a rib: Sushruta mildly overestimated. This is thought to be from him, largely basing his skeletal insights off child cadavers, before many bones have fused together (9). Hindu religious law calls for the cremation of any body over two years old, in its natural and thus undissected state; though there are accounts of Sushruta performing dissections, presumably on adults, the bodies he likely had the most exposure to were infants.

Sushruta was working within the confines of the society and world that he lived in, as was Herophilos. Medical insights which seem obvious to us today, like that the brain is for thinking and the heart is for beating blood, and that blood goes through the arteries and is most definitely a liquid, rely upon prior knowledge reached with tools that hadn’t even been invented yet. These firsts—surgeons, anatomists, scientists—would probably have to be physically pried away from microscopes and X-rays, if ever introduced to them. They often didn’t even have a human body to dissect, yet drew human anatomical conclusions regardless. And it’s easy to marvel at their mistakes, but it’s even easier to marvel at how much they got right; Herophilos correctly uncovered nerves and linked them to sensation and response, which is impressive in itself. Could you find a nerve in some meat, with just your naked eye? He also linked the heart and the pulse.

The Huangdi Neijing, for example, is a Chinese medical text said, though disputed, to be from 2600 BC, which describes the relationships between organs in military terms: the heart as a king, the liver as a commandant, and the gallbladder as an attorney-general responsible for coordination (10). However, both like and before Herophilos, it also correctly identifies the cyclic nature of blood flow and links it to the heart (10). The Edwin Smith Papyrus, dating from 1700 BC in Ancient Egypt, is the oldest known surgical text, describing 48 different injuries with treatments; all shockingly accurate (11). Sushruta may have miscounted the bones, but he described their shapes accurately and suggested legitimate therapies for particular bone breakages and dislocations. Nowadays, little has changed: in just the 1950s, lobotomies became the standard cure for a headache; even long after we developed microscopes, we were recommending treatments, like scrambling our brains, that only 70 years later seem ridiculously stupid. We’re far from done charting our own bodies, either. In 2018, an entirely new type of tissue all throughout the body was found: the interstitium, which is critical in cell and organ communication across the body (12). It’s been there the whole time, but no one had noticed before.

Humans are humans; it is only natural to want to understand ourselves, and as a part of that, our bodies. We now study our ancestors as they studied themselves; the same mix of awe, confusion and confidence. Their methods and conclusions may be fallible, but their curiosity was not, and as long as we remain, never will be, dead. These examples were only a fraction of those whose work has been preserved, who themselves were only a fraction of the ancient people across the globe who investigated human anatomy. A millennium from now, our descendants will laugh at our misconceptions, when they have mapped every neuron in the human brain with instruments we could not conceive of. But without us, they wouldn’t know what they know, and without our original anatomists, we wouldn’t know what we know. Our modern granular understanding of our own structure is built on the bodies we looked in before ours. So, we should perhaps extend some empathy to our predecessors. They had only eyeballs, a knife, and our own curiosity. Different tools, same bodies.

References

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