[Imagination involves creating a mental image of something that is
not present. Imagination is one of the key abilities that make us
human. But where did it come from?]
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TO IMAGINE IS HUMAN: AN EVOLUTIONARY HISTORY  
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Andrey Vyshedskiy
February 23, 2023
The Conversation
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_ Imagination involves creating a mental image of something that is
not present. Imagination is one of the key abilities that make us
human. But where did it come from? _

, agsandrew/Shutterstock.com

 

You can easily picture yourself riding a bicycle across the sky even
though that’s not something that can actually happen. You can
envision yourself doing something you’ve never done before – like
water skiing – and maybe even imagine a better way to do it than
anyone else.

Imagination involves creating a mental image of something that is not
present for your senses to detect, or even something that isn’t out
there in reality somewhere. Imagination is one of the key abilities
that make us human. But where did it come from?

I’m a neuroscientist
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who studies how children acquire imagination. I’m especially
interested in the neurological mechanisms of imagination. Once we
identify what brain structures and connections are necessary to
mentally construct new objects and scenes, scientists like me can look
back over the course of evolution to see when these brain areas
emerged – and potentially gave birth to the first kinds of
imagination.

From bacteria to mammals

After life emerged on Earth
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ago, organisms gradually became more complex. Around 700 million years
ago, neurons organized into simple neural nets
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and spinal cord [[link removed]] around 525 million
years ago.

Eventually dinosaurs evolved around 240 million
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mammals emerging a few million years later
[[link removed]]. While they shared the
landscape, dinosaurs were very good at catching and eating small,
furry mammals [[link removed]].
Dinosaurs were cold-blooded, though, and, like modern cold-blooded
reptiles, could only move and hunt effectively during the daytime when
it was warm [[link removed]]. To avoid
predation by dinosaurs, mammals stumbled upon a solution: hide
underground during the daytime
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Not much food, though, grows underground. To eat, mammals had to
travel above the ground – but the safest time to forage was at
night, when dinosaurs were less of a threat. Evolving to be
warm-blooded [[link removed]] meant
mammals could move at night. That solution came with a trade-off,
though: Mammals had to eat a lot more food than dinosaurs per unit of
weight in order to maintain their high metabolism
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inner body temperature around 99 degrees Fahrenheit (37 degrees
Celsius).

Our mammalian ancestors had to find 10 times more food
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time, and they had to find it in the dark of night. How did they
accomplish this task?

To optimize their foraging, mammals developed a new system to
efficiently memorize places where they’d found food: linking the
part of the brain that records sensory aspects of the landscape –
how a place looks or smells – to the part of the brain that controls
navigation. They encoded features of the landscape in the neocortex,
the outermost layer of the brain. They encoded navigation in the
entorhinal cortex. And the whole system was interconnected
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called the hippocampus. Humans still use this memory system
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events, such as your car and where you parked it.

Groups of neurons [[link removed]] in the
neocortex encode these memories of objects and past events.
Remembering a thing or an episode reactivates the same neurons
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mammals likely can recall and re-experience previously encoded objects
and events by reactivating these groups of neurons. This
neocortex-hippocampus-based memory system that evolved 200 million
years ago became the first key step toward imagination.

The next building block is the capability to construct a “memory”
that hasn’t really happened.

Involuntary made-up ‘memories’

The simplest form of imagining new objects and scenes happens in
dreams. These vivid, bizarre involuntary fantasies are associated in
people with the rapid eye movement (REM) stage of sleep.

Scientists hypothesize that species whose rest includes periods of REM
sleep also experience dreams [[link removed]].
Marsupial and placental mammals do have REM sleep, but the egg-laying
mammal the echidna does not, suggesting that this stage of the sleep
cycle evolved after these evolutionary lines diverged
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fact, recording from specialized neurons in the brain called place
cells [[link removed]]
demonstrated that animals can “dream” of going places they’ve
never visited before [[link removed]].

In humans, solutions found during dreaming can help solve problems
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scientific and engineering solutions spontaneously visualized during
sleep.

The neuroscientist Otto Loewi dreamed of an experiment that proved
nerve impulses are transmitted chemically
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immediately went to his lab to perform the experiment – later
receiving the Nobel Prize for this discovery.

Elias Howe, the inventor of the first sewing machine, claimed that the
main innovation, placing the thread hole near the tip of the needle,
came to him in a dream
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Dmitri Mendeleev described seeing in a dream “a table where all the
elements fell into place as required
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down on a piece of paper.” And that was the periodic table.

These discoveries were enabled by the same mechanism of involuntary
imagination first acquired by mammals 140 million years ago.

Imagining on purpose

The difference between voluntary imagination and involuntary
imagination is analogous to the difference between voluntary muscle
control and muscle spasm. Voluntary muscle control allows people to
deliberately combine muscle movements. Spasm occurs spontaneously and
cannot be controlled.

Similarly, voluntary imagination allows people to deliberately combine
thoughts. When asked to mentally combine two identical right triangles
along their long edges, or hypotenuses, you envision a square. When
asked to mentally cut a round pizza by two perpendicular lines, you
visualize four identical slices.

This deliberate, responsive and reliable capacity to combine and
recombine mental objects is called prefrontal synthesis. It relies on
the ability of the prefrontal cortex located at the very front of the
brain to control the rest of the neocortex.

When did our species acquire the ability of prefrontal synthesis?
Every artifact dated before 70,000 years ago could have been made by a
creator who lacked this ability. On the other hand, starting about
that time there are various archeological artifacts unambiguously
indicating its presence: composite figurative objects, such as
lion-man [[link removed]]; bone needles with an eye
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adorned burials suggesting the beliefs in afterlife
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Multiple types of archaeological artifacts unambiguously associated
with prefrontal synthesis appear simultaneously around 65,000 years
ago in multiple geographical locations. This abrupt change in
imagination has been characterized by historian Yuval Harari as the
“cognitive revolution
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Notably, it approximately coincides with
[[link removed]] the largest _Homo
sapiens_‘ migration out of Africa [[link removed]].

Genetic analyses suggest [[link removed]] that
a few individuals acquired this prefrontal synthesis ability and then
spread their genes far and wide by eliminating other contemporaneous
males with the use of an imagination-enabeled strategy and newly
developed weapons.

So it’s been a journey of many millions of years of evolution for
our species to become equipped with imagination. Most nonhuman mammals
have potential for imagining what doesn’t exist or hasn’t happened
involuntarily during REM sleep; only humans can voluntarily conjure
new objects and events in our minds using prefrontal synthesis.[The
Conversation]

Andrey Vyshedskiy
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Professor of Neuroscience, _Boston University
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This article is republished from The Conversation
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the original article
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* Science
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* Evolution
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* human origins
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* psychology
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