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The evolution of human vision dates back to the very first primates that evolved 55 million years ago, a study of a tiny mammal from Madagascar was found.
The world’s smallest primate, the endangered gray lemur, is no bigger than an apple and weighs only two ounces.
Swiss researchers have said that despite their small size, the visual system of the endangered gray mouse lemur is just as large as that of other primates.
In fact, more than a fifth of the brain of the big-eyed mammal is dedicated to visual processing – compared to just three percent of the human brain.
The discovery highlights the incredible preservation and importance of this region of the brain to our daily lives – and that of our ancestors in the distant past.
The evolution of human vision dates back to the very first primates that evolved 55 million years ago, a study of a tiny mammal from Madagascar, pictured, has been found
“This study also highlights the critical importance of conserving the habitat of primate species such as the mouse lemur, especially in the forests of Madagascar,” said author and neuroscientist Daniel Huber, from the University of Geneva.
“These habitats are disappearing at an alarming rate, taking with them valuable keys to understanding our own origins.
Primates – including humans – process images using small computing units located in the visual cortex of their brains.
The primate visual system has fascinated biologists for over a century because it is unique among mammals, including rodents.
“With the different species of primates covering a wide range of sizes, we were left to wonder if this basic unit of calculation fits the size of the body or the brain,” explained Professor Huber.
“Is it simplified or miniaturized, for example, in the world’s smallest primate, the gray mouse lemur?” He asked.
In experiments using an optical brain scanner, geometric shapes representing lines of different orientations were presented to lemurs and the activity of neurons was imaged.
Repeating such measurements gradually allowed the researchers to determine the size of the brain unit processing the form information.
“We expected to see a unit of small size, proportional to the small size of the lemur, but our data revealed that they were more than half a millimeter in diameter,” explained Professor Huber.
The world’s smallest primate, the endangered gray lemur (pictured) is no bigger than an apple and weighs just two ounces
Researchers compared hundreds of these units in the tiny mouse lemur brain with data obtained for the visual circuits of other much larger primate species.
Surprisingly, the basic processing unit was almost identical in size in the mouse lemur, as in the large primates.
These included monkeys such as macaques weighing more than a stone, or even larger primates – such as humans.
The arrangement of the units across the brain was also completely indistinguishable, following the same rules with mathematical precision. And the number of nerve cells was equal.
The author of the article Fred Wolf – of the Max Planck Institute in Göttingen, Germany – predicted that universal mathematical principles would govern the evolution of the visual system ten years ago, but even he said he was amazed. of the degree of invariance found.
“55 million years of separation on different continents is a very long evolutionary path to travel,” he added.
“I would have expected a mixture of general similarities and characteristic differences between species in these neural modules. But the point is simply that [that] it is practically impossible to tell them apart.
Swiss researchers have said that despite their small size, the visual system of the endangered gray lemur is just as large as that of other primates.
The results It sheds new light on the origins of primate vision. The fact that this unit is so well preserved suggests that it evolved very early.
When it comes to forming images, our primate ancestors had abilities similar to ours from the start.
It also cannot be compressed or miniaturized. A fixed number of neurons is required to ensure its optimal functionality.
“ For tiny primate species with excellent vision, like the mouse lemur, therefore, the visual system must be relatively large, compared to the size of their entire brain, to accommodate a sufficient number of units. visual processing, ” said Professor Huber..
The full results of the study were published in the journal Current Biology.
The evolution of human vision dates back to the very first primates that evolved 55 million years ago, a study of a small mammal from Madagascar has been found
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