What Yakushi Nyorai Teaches UsAs someone who graduated from a school of pharmacy and holds a pharmacist's license, I can't help but feel a special connection to the figure of Yakushi Nyorai (the Medicine Buddha). When I see a statue of Yakushi Nyorai at a temple, I immediately recognize it—by the medicine jar held in the left hand. And flanking this central figure are two attendant bodhisattvas: Nikkō Bosatsu (Sunlight Bodhisattva) and Gakkō Bosatsu (Moonlight Bodhisattva).When you think about it carefully, this composition is quite fascinating. The sun and moon—the most magnificent celestial bodies to ancient peoples—are positioned merely as supporting figures on either side. At the center stands the "Medicine Master," one who handles medicinal substances. This arrangement seems to reflect just how much hope and reverence people of that era placed in medicine and healing.We who are accustomed to modern medicine think that when we fall ill, we can simply go to the hospital. But for people in the past, illness was an unreasonable threat—striking without known cause or predictable timing. It was natural for people to turn to prayer and Buddhist chanting when facing something whose cause they couldn't understand. But that alone wasn't enough. If "pharmaceutical treatment" was discovered as a means that provided more tangible effects than prayer, and if this eventually became deified, then the birth of Yakushi Nyorai as a figure makes perfect sense.Incidentally, there's another intriguing theory about the origin of the attendant bodhisattvas Nikkō and Gakkō. The ancient Indian medical classic "Charaka Samhita," a foundational text of Ayurveda, contains unique teachings about preparing medicine. According to this text, medicine should be decocted under sunlight and cooled under moonlight to enhance its potency. If this teaching influenced the worship of Yakushi Nyorai, then the presence of the Sunlight and Moonlight Bodhisattvas would signify that the Medicine Buddha manifests divine power by borrowing the forces of sun and moon. It's a highly suggestive episode that reveals how deeply ancient medicine and religion were intertwined.5,000 Years of Pharmaceutical TreatmentLet's broaden our perspective from Yakushi Nyorai and look at the history of medicine itself. When did humanity first begin using medicinal substances?The "Charaka Samhita" I mentioned earlier is believed to have been written over 2,000 years ago. But the history of medicine extends even further back. China has a medical text called the "Huangdi Neijing" (Yellow Emperor's Inner Canon), which also dates back more than 2,000 years. In Egypt, a medical document known as the "Ebers Papyrus" records hundreds of medicines and treatments; this scroll dates to around 1500 BCE. Going back even further, records from ancient Mesopotamia approximately 5,000 years ago show prescriptions and herbal therapies inscribed on clay tablets.Tracing these records makes it undeniable that humanity has been using medicine for thousands of years. What's particularly noteworthy is that all these records were created after the invention of writing. Since medicine already existed when writing emerged, it's certain that the origins of medicine extend into prehistoric times—before written records began.So how can we learn about medicine from the pre-literate era? Sometimes archaeological excavations provide clues, but there's another, quite unexpected approach that has shed light on this question: observing the behavior not of humans, but of animals closely related to us. If other primates use medicine, then the practice of using medicinal substances might date back to before humans became human. And indeed, remarkable discoveries suggesting exactly this have been reported.An Orangutan Using Topical MedicineIn May 2024, a research team led by Dr. Isabelle Laumer from the Max Planck Institute in Germany published a paper in the journal "Scientific Reports." It described how a wild orangutan living in the rainforests of Sumatra, Indonesia, used a plant to treat a wound.The research team had been observing a male orangutan they named Rakus. One day, they noticed Rakus had a wound on his face. Male orangutans sometimes fight fiercely over territory and females. He had likely been injured in such a conflict. As they continued observing, the wound began to suppurate after about three days. If it worsened, there was danger of infection.But Rakus did something beyond what the researchers expected. He plucked leaves from a plant called "Akar Kuning" in the forest and began chewing them. What's important here is that orangutans rarely eat Akar Kuning. Even putting it in their mouths is documented as extremely unusual behavior. In other words, Rakus wasn't chewing this plant to satisfy hunger.Rakus spent about 30 minutes carefully chewing the leaves until they formed a paste. Then, for seven minutes, he thoroughly applied this paste to his wound. It was clearly intentional and deliberate behavior, as if applying ointment. Even more remarkably, after application, he made gestures as if covering the affected area with leaves to prevent flies and other insects from approaching the wound.The subsequent progress is also noteworthy. Five days after applying the Akar Kuning paste, the wound began to close, and it was nearly healed after one month. Of course, we cannot definitively conclude that the medicine was effective based on this alone. Natural healing power certainly played a role. However, the fact that a wound that had begun to suppurate recovered so smoothly strongly suggests that Akar Kuning's components played some role.Actually, Akar Kuning has long been used as a medicinal plant by local people in Sumatra. It has been scientifically confirmed to contain compounds with anti-inflammatory, antibacterial, and even analgesic properties. Was Rakus's choice of this plant coincidental? Or did he somehow know of its medicinal properties?In Africa, chimpanzees have long been known to swallow certain medicinal plants to expel intestinal parasites. By deliberately swallowing leaves whole without chewing, the rough fibrous surface of the leaves catches parasites in the intestines and expels them. This behavior, called "self-medication," has become an important theme in primate research.However, what had been observed until now was exclusively oral administration—drinking medicine through the mouth. The use of a plant chewed into paste and applied directly to an affected area as "topical medicine" was confirmed in wild animals for the first time with Rakus's case. This isn't merely a story about finding unusual behavior. It's a groundbreaking discovery showing that the distinction between "internal" and "external" use of medicine can exist in animals other than humans.The Origin of "Medicine" and the Miracle of AnimalsLearning about Rakus's behavior makes us reconsider the origins of medicine. When and how did we humans begin using medicine?One clue is hidden in language. The etymology of the Japanese word "kusuri" (medicine) has various theories, but one prominent explanation traces it to "kusa" (grass). The idea is that people discovered beneficial effects from grasses and plants growing around them and came to call these "kusuri." Indeed, many modern pharmaceuticals contain plant-derived components. Salicylic acid, the basis of aspirin, was discovered in willow bark, and quinine, a malaria treatment, was obtained from cinchona bark. The history of medicine is also a history of our relationship with plants.On the other hand, there's also a theory that "kusuri" derives from "kusushi," meaning mysterious or miraculous. "Kusushi" is an archaic term expressing something wondrous and mystical. When a person suffering from illness consumed the juice of grass or trees and their symptoms mysteriously eased—that "miraculous" experience might have given birth to the word "kusuri."This "kusushi" etymology becomes oddly convincing when considering Rakus's behavior. An orangutan living in the forest deliberately selects a plant it doesn't normally consume, carefully chews it into a paste, and applies it to a wound. This sequence of actions is something we might want to call a "miracle."Of course, interpreting this too mystically isn't scientific. The behavior of animals consuming specific plants when unwell might be instinctive wisdom acquired through long evolutionary processes, or it might result from individual learning and accumulated experience. It's also possible they learned by observing mothers or companions. But in any case, it's now clear that using medicine isn't exclusively a human practice.The clay tablets of Mesopotamia from 5,000 years ago, ancient Egyptian papyri, Indian Ayurveda, Chinese medical texts—and in Japan, Yakushi Nyorai. Humanity has discovered and developed medicine across the world within their respective cultures. Tracing the roots of these endeavors, we might arrive at the image of an orangutan in the Sumatran rainforest applying medicinal herbs to a wound.What kind of medicine is contained in the medicine jar that Yakushi Nyorai holds in his left hand? Perhaps it's not something humans invented, but rather nature's blessing itself—something animals have been finding in forests since ancient times. Rakus's behavior quietly teaches us that the history of medicine is far older and deeper than we imagine.ReferencesLaumer IB, et al. "Active self-treatment of a facial wound with a biologically active plant by a male Sumatran orangutan." Scientific Reports, May 2024"Charaka Samhita" — Classical Ayurvedic medical text from ancient India"Huangdi Neijing" (Yellow Emperor's Inner Canon) — Ancient Chinese medical text"Ebers Papyrus" — Ancient Egyptian medical document (circa 1500 BCE)Records of herbal therapy on clay tablets from ancient Mesopotamia