Those cobras with proto-eyes were most likely to elicit our sympathy from ancient myths, and so to escape the scythe. In his book Snakes: The Evolution of Mystery in Nature (1997), the herpetologist Harry Greene speculates that humans’ sympathetic perception of snakes in places where they’re associated with myths and legends might have selected for the origin of cobra eyes.

It’s possible that these mythological gestures of goodwill have had real evolutionary consequences for existing snakes. One of them supports Narayana, the supreme deity, in the cosmic ocean while he holds up the world.

A cobra allegedly spread its hood to shelter Siddhartha Buddha from the rain while he meditated under a tree and, in Hindu mythology, the Naga are benevolent serpent folk. At the same time, however, snakes occupy a vaunted place in some aspects of Buddhism and Hinduism. Humans have an understandably antagonistic relationship with serpents, often killing them upon encounter.

Venomous snakebites are a major threat to public health, leading to approximately 50,000 fatalities every year. In India, humans frequently encounter snakes. However, we might make headway by considering the cobra’s number-one predator: humans. This is a tempting explanation but seems unlikely, since the pattern is highly regular, and the eyes’ position on the hood makes it particularly visible. One might think that the cobra’s eyes originated by chance from among all this wild diversity, and that selection had no role in their evolution. Its fauna includes legions of venomous elapids (the family that contains cobras), along with various vipers, constricting pythons, skinny vine snakes, aquatic keelbacks, four of the world’s ‘flying’ snakes, vermicious caecilians, monitor lizards, the whimsical yet hopeless-looking balloon frog, and unorthodox crocodilians such as the gharial. India is a marvellous region for reptiles and amphibians. Some of the most convincing false eyes are found on the spectacled cobra of India, Naja naja. Why would natural selection favour the assemblage of the complex genetic machinery needed for false eyes, or for that matter, the thousands of other complex signals we find in nature? Photo courtesy Krushnamegh Kunte So, anything that appears striking and unambiguous should do the trick – and if there are fewer complexities that could go awry during development, or be misinterpreted, so much the better. After all, the function of warning signals depends on making it obvious to the predator that this potential piece of prey is not to be meddled with. Instead, the cobra could have opted for just a bit of red around the neck, which other venomous snakes possess. A cobra could probably warn off predators with a much simpler design that’s less trouble to manufacture than its wide hood, eerily recognisable eyes, and even a definite ‘nose’ between the eyes. In fact, it’s so beautifully simple that it raises the question of why warning signals should evolve into such complex forms in the first place. The function of the cobra’s hood is intuitive, and squares nicely with how we often expect evolution to work. The cobra’s false eyes are a likely example of warning signals: adaptations that prey use to tell potential predators: ‘If you attack me, I promise things will go badly for you.’ Both predator and prey benefit from this message: the prey has the chance to avoid an attack, and the predator can make an informed decision about whether or not to risk pouncing on a well-defended meal. The story’s author, Rudyard Kipling, meticulously describes the false eyes that some cobras have on the back of their hoods: nch by inch out of the grass rose up the head and spread hood of Nag, the big black cobra, and he was five feet long from tongue to tail … he spread out his hood more than ever, and Rikki-tikki saw the spectacle-mark on the back of it that looks exactly like the eye part of a hook-and-eye fastening… In a dramatic scene that some readers will recall from childhood, the mongoose Riki-tikki-tavi encounters the villainous cobra Nag for the first time.

Eye orientation of predator vs prey