For human babies, faces are fascinating. Soon after birth a baby will become fixated on their mother’s face, preferring to look at them over anyone else. Now, a new study published in the journal Proceedings of the National Academy of Sciences has shown that this human obsession with faces is shared by an unexpected member of the animal kingdom: tortoises.
The study took a selection of tortoise hatchlings from the Testudo genus and placed them in an arena with four images to choose from. Three were a random assortment of black shapes but one had black marks spaced in a way that was similar to a face, depicting what could be perceived as two eyes and a mouth. They tried out the experiment on 136 hatchlings across five Testudo species and found that the tortoises favored the faces in 70 percent of cases. Their selection was identified when the tortoises oriented themselves toward the object, whether turning or marching their tiny limbs over to it, as seen in the video below.
At this point, it’s worth mentioning that tortoises aren’t the only animals that have been found to do this, the same has been seen in monkeys, dogs, and even chickens. What makes tortoises' affinity for faces so interesting, however, is that these animals don’t experience parental care like all the others. When a mother tortoise lays her eggs, she essentially leaves them to it and is long gone before any of the hatchlings peep their heads out of the ground. These solitary tortoises then head on their merry way to spend the majority of their lives alone.
And yet, when faced with a choice of meaningless shapes, the majority of Testudo tortoises appeared to favor the one that looked like a face. The study authors suggest this hints at the possibility that preferring faces early in life is common across animals. They propose it is a shared trait seen in seemingly unrelated species that were linked long ago in the evolutionary tree. If their hypothesis is correct, it shows that newborns’/hatchlings’ preference for faces must predate the emergence of parental care.
“If early face-like preference evolved in the context of parental care, solitary species should not exhibit it,” the authors wrote. “The predisposition to approach face-like stimuli observed in hatchlings of these solitary species suggests the presence of an ancient mechanism, ancestral to the evolution of reptiles and mammals, that sustains the exploratory responses, and potentially learning, in both solitary and social species.”