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The evolution of human vision can be traced back to the very first primates that evolved 55 million years ago, according to a study of a tiny mammal from Madagascar.
The smallest primate in the world, the endangered gray mouse lemur, is no larger than an apple and weighs only two ounces.
The Swiss researchers said that despite their small size, the endangered gray mouse lemur’s visual system is as large as that of other primates.
In fact, more than a fifth of the big-eyed mammal’s brain is devoted to visual processing, compared to just three percent of the human brain.
The discovery highlights the incredible conservation and importance of this brain region for our daily life and those of our ancestors in the distant past.
The evolution of human vision can be traced back to primate primates that evolved 55 million years ago, a study of a tiny mammal from Madagascar, pictured, found
“This study also highlights the crucial importance of conserving the habitat of primate species such as the mouse lemur, particularly in the forests of Madagascar,” said article author and neuroscientist Daniel Huber of the University of Geneva.
“These habitats are disappearing at an alarming rate, carrying with them precious keys to understanding our origins.”
Primates, including humans, process images using small computing units located in the visual cortex of their brains.
The visual system of primates has fascinated biologists for more than a century as it is unique among mammals, including rodents.
‘As different primate species cover a wide range of sizes, we wondered whether this basic computing unit fits the size of the body or the brain,’ explained Professor Huber.
“Is it simplified or miniaturized, for example, in the smallest primate in the world, the gray mouse lemur?” churches.
In experiments using an optical brain scanner, geometric shapes representing lines of various orientations were presented to the lemurs and the activity of neurons was imaged.
Repeating these measurements gradually enabled the researchers to determine the size of the brain unit that processes the module’s information.
‘We expected to see a small unit, proportional to the small size of the lemur, but our data revealed that they measure more than half a millimeter in diameter,’ explained Professor Huber.
The smallest primate in the world, the endangered gray mouse lemur (pictured) is no bigger than an apple and weighs just two ounces
The researchers compared hundreds of these units in the small brain of mouse lemur with data obtained for the visual circuits of other, much larger primate species.
Surprisingly, the core processing unit was nearly identical in size in the mouse lemur as it was in larger primates.
These included monkeys such as macaques that weighed more than a stone, or even larger primates, such as humans.
The arrangement of the units across the brain was also totally indistinguishable, following the same rules with mathematical precision. And the number of nerve cells was the same.
Article author Fred Wolf – of the Max Planck Institute in Gottingen, Germany – predicted that universal mathematical principles would govern the evolution of the visual system a decade ago, but he too said he was surprised by the degree of invariance found.
“55 million years of separation on different continents is a very long evolutionary path to go,” he added.
“I would have expected a mix of general similarities and characteristic differences between species in these neural modules. But the fact of the matter is simply [that] it is practically impossible to distinguish them.
Swiss researchers said that despite their small size, the endangered gray mouse lemur’s visual system is as large as that of other primates.
The Results Shed new light on the origins of the primate view. The fact that this unit is so well preserved suggests that it evolved very early on.
When it comes to image forming, our primate ancestors had similar abilities 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 eyesight, such as the mouse lemur, the visual system must therefore be relatively large, relative to the size of their entire brain, to accommodate enough visual processing units,’ said Prof. Huber.
The full results of the study were published in the journal Current Biology.
The evolution of human vision can be traced back to primate primates that evolved 55 million years ago, a study on a tiny mammal from Madagascar found
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