Evolution: Human vision can be traced back to the very first primates from 55 million years ago


The evolution of human vision can be traced back to the very first primates that evolved 55 million years ago, a study of a small mammal from Madagascar found.

The smallest primate in the world, the endangered gray mouse lemur, is no bigger than an apple and weighs just two grams.

Researchers from Switzerland said that despite their small size, the endangered gray mouse lemur’s visual system is just as large as that of other primates.

In fact, more than a fifth of the brains of large-eyed mammals is devoted to visual processing – compared to just under three percent of the human brain.

The find highlights the incredible preservation and importance of this brain region for our daily lives – and that of our ancestors in the distant past.

Human vision evolution can be traced back to the very first primates that evolved 55 million years ago, study of small mammal from Madagascar, pictured, found

Human vision evolution can be traced back to the very first primates that evolved 55 million years ago, study of small mammal from Madagascar, pictured, found

“This study also highlights the critical importance of preserving the habitat of primate species such as the mouse lemur, particularly in the forests of Madagascar,” said author and neuroscientist Daniel Huber of the University of Geneva.

“These habitats are disappearing at an alarming rate and carry valuable keys to understanding our own origins.”

Primates – including humans – process images using tiny computing units in the visual cortex of their brains.

The visual system of primates has fascinated biologists for more than a century because it is unique among mammals, including rodents.

“Since the different primate species cover a wide range of sizes, we wondered whether this basic computer can be adapted to the size of the body or brain,” explains Professor Huber.

Has it been simplified or miniaturized, for example in the world’s smallest primate, the gray mouse lemur? ‘ he asked.

In experiments with an optical brain scanner, geometric shapes representing lines of different orientations were presented to lemurs and the activity of neurons was mapped.

The repetition of such measurements allowed the researchers to gradually determine the size of the brain unit that processes form information.

“We expected to see a small unit proportional to the lemur’s small size, but our data showed they are over half a millimeter in diameter,” explains Professor Huber.

The world's smallest primate, the endangered gray mouse lemur (pictured), is no bigger than an apple and weighs just two ounces

The world's smallest primate, the endangered gray mouse lemur (pictured), is no bigger than an apple and weighs just two ounces

The world’s smallest primate, 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 cerebellum of mouse lemurs with data obtained for the visual circuits of other much larger primate species.

Surprisingly, the basic 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 rock, or even larger primates – such as humans.

The division of units across the brain was also totally indistinguishable, following the same rules with mathematical precision. And the number of nerve cells was the same.

Paper author Fred Wolf – of the Max Planck Institute in Gottingen, Germany – predicted that a decade ago universal mathematical principles would drive the evolution of visual systems, but even he said he was amazed at the degree of immutability found.

“55 million years of separation on different continents is a very long evolutionary road to travel,” he added.

‘I would have expected a mix of general similarity and characteristic differences between species in these neural modules. But the fact is just like that [that] it is practically impossible to tell them apart. ‘

Researchers from Switzerland said that, despite their small size, the endangered gray mouse lemur's visual system is as large as that of other primates.

Researchers from Switzerland said that, despite their small size, the endangered gray mouse lemur's visual system is as large as that of other primates.

Researchers from Switzerland said that despite their small size, the endangered gray mouse lemur’s visual system is just as large as that of other primates.

The Findings 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 the same skills as ours from the beginning.

It also cannot be compressed or miniaturized. A fixed number of neurons is required to ensure optimal functionality.

“For small primate species with excellent vision, such as the mouse lemur, the visual system must therefore be relatively large, compared to the size of their entire brain, to accommodate a sufficient number of visual processing units,” said Prof Huber..

The full findings of the study have been published in the journal Current Biology.

The evolution of human vision can be traced to the very first primates that evolved 55 million years ago, a study of a small mammal from Madagascar found

The evolution of human vision can be traced to the very first primates that evolved 55 million years ago, a study of a small mammal from Madagascar found

The evolution of human vision can be traced to the very first primates that evolved 55 million years ago, a study of a small mammal from Madagascar found

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