Divine Light: What do an Ibis, Baboon and the God of the Moon Have in Common?

Researchers used a spectrometer to test a long-standing question about why Egypt paired a bird and a baboon with its moon god

A few weeks ago, I was walking around an Egyptian museum with my partner. After a few minutes of looking at various depictions of ibises and Thoth and reading the accompanying display descriptions, we looked up at each other, and both wondered the same thing: Why use an ibis to depict the god of wisdom?

Let me explain: in South Africa, we have several ibis species, but I will focus on two: the hadeda ibis (Bostrychia hagedash) and the sacred ibis (Threskiornis aethiopicus). The sacred ibis, while it looks majestic, if you have ever been near one of their nesting grounds, you know, they smell foul! The hadeda, on the other hand, is stupid; it is very much ‘bird-brained’. So, with this being my partner’s and my working knowledge of the ibis, stupid and smelly, we wondered, why oh why use the ibis to depict the god of wisdom, writing, and the moon?

A recent study by Nathaniel Dominy and Catherine Hobaiter may finally have given us the answer the museum couldn’t. You see, Thoth was not just linked to the ibis (particularly the sacred ibis), but also to the sacred baboon (Papio hamadryas). And what do they have in common with each other? They are both silvery-white.

Let me explain.

Thoth, Ibises, and Baboons

The Egyptian god Thoth was synonymous with many things, among them were the moon, cosmic order, writing, wisdom, and magic. According to Egyptian myth, he appeared in two forms, the sacred ibis and the baboon.

The sacred ibis is a white-feathered bird with black legs, a black head, and a black beak. It can be found basically across sub-Saharan Africa. In antiquity, it also called Egypt home, though its wild populations ceased to exist there in the 1700s.

Why it came to represent Thoth has been a matter of debate; some say its curved beak echoes a crescent moon, while others point to its black-and-white markings when it folds its wings, resembling a quarter moon. Others still say its white plumage may link to Thoth’s Egyptian name Ḏḥw.ty, meaning “white/bright thing”.

As for the baboon, well, it’s a bit harder to explain. Baboons never lived in Egypt, at least not during the Holocene, making it a rare addition as just about every other animal represented in the Egyptian pantheon was also native to the land.

This said, baboons were traded to Egypt, and among the most common species were the olive baboon (P. anubis) and the sacred baboon, whose remains have been recovered from temples and tombs spanning centuries.

Personally, I thought the baboon may have come to represent Thoth, as they are incredibly intelligent. We have colonies of Chacma baboons (P. ursinus) in South Africa. They are intelligent, known for their advanced social cognition, problem-solving, and adaptability, but they are also very dangerous, so I stay far away from them.

But if intelligence was the only factor the ancient Egyptians considered when linking their god of wisdom to baboons, one wonders why not the olive baboon? And again, why the ibis?

A possible answer comes from Thoth’s name. Recent linguistic work has traced Thoth’s name, Ḏḥw.ty, to ancient Afroasiatic words describing the brightness of the moon, alongside epithets such as ‘the beautiful one of the night’, ‘the brightly shining’, and ‘silver sun’.

The sacred baboon, unlike olive or chacma baboons, is silvery grey, resembling the moon in color. In fact, in German, their names “Graupavian” or “Silberpavian” mean “grey baboon” and “silver baboon,” respectively, a nod to their coloring.

To test whether this color association holds up, the researchers took a rather novel approach, one which, unlike the impressions of the human eye, doesn’t depend on individual perception.

Silvery Beauty of the Moon

One of the first things we learned in school about the moon is that, unlike the sun, most of its light is reflected sunlight, just around 500,000 times fainter.

The wavelength of light is what determines our perception of color. Moonlight’s spectrum is smooth and fairly flat, peaking in the visible range between 600 and 700 nanometers (nm), making it appear silvery-grey to the human eye.

To determine whether sacred baboons and sacred ibises share this coloring, the researchers compared two sets of measurements. For moonlight, they drew on an earlier study recorded in Sabah, Malaysia, in July 2011. For the animals, they used a spectrometer (an instrument that records how much light of each wavelength a surface reflects) on specimens of olive baboon, sacred baboon, and sacred ibis held at the American Museum of Natural History in New York.

While olive baboon hair peaked between 525 and 650 nm, which the human eye reads as greenish (hence the common name ‘olive’), in the sacred baboon hair, it peaked between 600 and 700 nm, an almost exact match to moonlight.

Male and female sacred baboons look strikingly different: females and youngsters have short olive-brown hair, while mature males grow a thick silver-grey cape over the shoulders and bright white cheek ruffs. This explains why the male sacred baboon came to represent Thoth.

And what about the ibis? Well, the Egyptians had three species of ibis to choose from: the hermit ibis (Geronticus eremita), which looks like a deranged old bald man; the glossy ibis (Plegadia falcinellus), which honestly looks like a shiny version of the hadeda; and the sacred ibis which I just learnt its Afrikaans name, “skoorsteenveër” means chimney sweeper because it apparently looks like it uses its head for this purpose (does that make Thoth the god of chimney sweepers?).

Okay, back to being serious.

Of these three ibis species, the Egyptians chose the sacred ibis, and when its plumage was examined with the spectrometer, it too had a nearly identical spectral profile to moonlight.

The evidence suggests these animals were chosen to represent Thoth because of their color. Alongside evidence of color, classical texts describe how baboons behave when the sun and moon align. The fullest account appears in the Hieroglyphica, a fifth-century compilation attributed to the Egyptian sage Horapollo Niliacus. Niliacus says

“When [Egyptians] portray the moon … they paint [Papio hamadryas] because this animal has a certain sympathy at its conjunction with the god.”

He explains that during a solar eclipse, the male baboon refuses to look up or eat, instead crouching on the ground as if mourning the moon’s disappearance. He also details that baboons were kept in temples precisely so that these conjunctions could be detected.

Modern observations have reported that captive sacred baboons abruptly stop their usual activities during solar eclipses, becoming watchful and huddling together, likely due to anxiety.

One study also noted that baboons began to vocalize as an eclipse waned, an act that may have carried religious weight to the ancient Egyptians since Egyptian texts speak of the “jubilating language” of baboons greeting the sun, a sacred speech shouted, sung, and danced, which Egyptians hoped to decipher as a route to divine knowledge.

So, the sacred ibis and the sacred baboon may have been chosen not for their intelligence, not for being native to Egypt, but for their color. A color perception proven through spectrometry. Thoth was the god of the moon, and his animal counterparts matched him.

A recent study by Dr. Dominy and Dr. Hobaiter used a spectrometer to compare the plumage of the sacred ibis and the hair of the male sacred baboon against measurements of moonlight. They found that both animals reflect light almost exactly as the moon does, suggesting the ancient Egyptians may have chosen these animals to depict their god of the moon, wisdom, writing, and magic because of their silvery color.

Now, when I visit any other Egyptian museum, I no longer have to wonder why an ibis was chosen to depict Thoth. Instead, I will simply wonder at the remaining pantheon, like Set. What is he? To me, he looks a bit like an aardvark, but I have no idea if those live anywhere near Egypt.

Do you think the sacred ibis and baboon were chosen for their color, or can you think of another reason? And what other animals shimmer like the moon?

Let me know your thoughts, and if you’d like to support the countless hours I pour into researching, writing, and bringing these hidden corners of history to life, why not Buy Me A Coffee

Reference

Dominy, N. J., & Hobaiter, C. (2026). Moonlight and the apotheosis of sacred baboons. Time and Mind, 1–12. https://doi.org/10.1080/1751696X.2026.2696260