Carved from green stone and placed on the chest of the deceased, dung beetles stood in for the ancient Egyptians’ hearts during mummification. On their base they carried inscriptions designed to prevent the heart from testifying against the deceased during the trial of the dead. They helped pass the test of the scales, in which Anubis, the jackal-headed god, weighed the hearts and determined whether or not the person was worthy to enter the realm of the dead.
The insect was not only an amulet for the afterlife, but reincarnated transformation, renewal and resurrection. It was the symbol of the morning sun. The dung beetle mirrored the sun’s journey across the sky, as Plutarch wrote: “Its sperm is a round pellet of material that rolls in the opposite direction, just as the sun seems to return to the heavens in the opposite direction.” to its own course, which is from west to east. Today we know that it is not the beetles that drive the movement of the sun, but it is he who directs the movement of these peculiar insects, just as the distant stars of the Milky Way and the Moon do.
There are many types of dung beetles, in fact, of the 8,000 known species of dung beetles, those that feed on dung, about 600 roll balls like the ones that so fascinated the ancient Egyptians. Molding the poop into a sphere is a good strategy for running away from the poop. The manure of dromedaries, donkeys, cows and any other large mammal is immediately filled with hundreds or thousands of saprophagous beetles that feed on the “waste” and make it disappear. To prevent rivals from stealing their cargo and running out of food, a fast and efficient dung escape strategy has been selected throughout evolution: a perfectly straight line in any direction.
Said like that, it doesn’t sound very surprising, but close your eyes and try to walk in a straight line. You will be surprised how difficult it is. In fact, It has been shown experimentallyboth in a German forest and in the Sahara desert, that blindfolded and without a point of reference, people immediately walk in circles, where the small irregularities of the terrain direct our steps. Dung beetles can describe a straight line everything and not seeing where they are going, as they move backwards, pushing the balls with their hind legs and with their heads facing the ground.
They do it by following the position of the sun, so much so that, if the sun is reflected in a mirror, and the real one is hidden, it is possible to alter the direction of the beetle in search of the reflection. When the sun is at its zenith and does not provide information about which way is east or west, it has been observed that they can be guided by the wind detected through their antennas. In deserts like the Kalahari, the wind blows strongest, driven by heat from the ground, when the sun is at its highest point. The constant movement of the wind allows them to maintain a straight course for a few minutes before burying themselves with their precious treasure under the ground. If one signal fails, they use another..
The nocturnal species are carried away by the light of the moon polarized by the Earth’s atmosphere. Other insects such as bees and ants can navigate by polarized light from the Sun, but to date, dung beetles are the only ones capable of doing so in polarized light from the moon, millions of times dimmer than that of the sun. some species they can even navigate by following the band of light drawn by the Milky Way in the night sky. No other animal is known to use this signal to navigate. Unlike nocturnal migratory birds, and sailors of the past, who used specific constellations to orient themselves, the beetles are guided by the brightness gradient of the night sky caused by the Milky Way. A less sophisticated system than that of birds and humans, but efficient enough to interpret the complex information present in a starry sky.
Surprisingly, they only know how to navigate by the skies, when some researchers decided to dress them with tiny visors so that they could not see the sky, they walked in circles like the people in the experiments carried out in the German forests. They also do not use terrestrial reference points, something that also makes them unique in the animal world: they use visual cues to orient themselves, but they ignore the reference points, however, before starting their journey, the beetles climb on the ball of dung and, for a few seconds, perform a dance, turning on it, during which they “photograph” the firmament, the characteristics of the sky before starting their journey, will those be their references as they move? They are small creatures, with brains the size of a poppy seed, but capable of using the sun, wind and stars to guide them. How do they solve such complex navigation tasks with such apparently simple nervous systems? Studying them will not lead us to the world of the dead, but perhaps to a possible optimization of targeting and search algorithms.
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