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  • The human brain is one of the most sophisticated organs in the world,

  • a supercomputer made of billions of neurons

  • that processes and controls all of our senses, thoughts, and actions.

  • But there was something Charles Darwin found even more impressive:

  • the brain of an ant,

  • which he called one of the most marvelous atoms of matter in the world.

  • If you find it hard to believe that something so tiny

  • could have a complex brain,

  • you're not alone.

  • In his project to classify and describe all living things,

  • Swedish naturalist Carl Linnaeus assumed insects had no brains at all.

  • He was wrong, but understandably so.

  • Insect brains are not only miniscule,

  • but in many respects, they function differently than our own.

  • One of the most noticeable differences

  • is that an insect that loses its head can still walk,

  • scratch itself,

  • breathe,

  • and even fly.

  • This is because while our nervous system works like a monarchy,

  • with the brain calling the shots,

  • the insect nervous system works more like a decentralized federation.

  • Many insect activities, like walking or breathing,

  • are coordinated by clusters of neurons, also known as ganglia,

  • along their bodies.

  • Together with the brain, these local ganglia form the insect nervous system.

  • While an insect can do a lot with just its local ganglia,

  • the brain is still crucial for its survival.

  • An insect's brain lets it perceive the world through sight and smell.

  • It also chooses suitable mates,

  • remembers locations of food sources and hives,

  • regulates communication,

  • and even coordinates navigation over huge distances.

  • And this vast diversity of behaviors

  • is controlled by an organ the size of the head of a pin,

  • with less than one million neurons,

  • compared to our 86 billion.

  • But even though the insect brain is organized very differently from ours,

  • there are some striking similarities.

  • For example, most insects have smell detectors on their antennae,

  • similar to those found in human noses.

  • And our primary olfactory brain regions look and function rather similarly,

  • with clusters of neurons activated and deactivated in precise timing

  • to code for specific scents.

  • Scientists have been astonished by these similarities

  • because insects and humans are not very closely related.

  • In fact, our last common ancestor was a simple worm-like creature

  • that lived more than 500 million years ago.

  • So how did we end up with such similar brain structures

  • when our evolution took almost entirely different paths?

  • Scientists call this phenomenon convergent evolution.

  • It's the same principle behind birds, bats, and bees separately evolving wings.

  • Similar selective pressures can cause natural selection

  • to favor the same evolutionary strategy

  • in species with vastly different evolutionary pasts.

  • By studying the comparison between insect and human brains,

  • scientists can thus understand which of our brain functions are unique,

  • and which are general solutions to evolutionary problems.

  • But this is not the only reason scientists are fascinated by insect brains.

  • Their small size and simplicity makes it easier to understand

  • exactly how neurons work together in the brain.

  • This is also valuable for engineers,

  • who study the insect brain to help design control systems

  • for everything from self-flying airplanes to tiny search-and-rescue roach bots.

  • So, size and complexity are not always the most impressive things.

  • The next time you try to swat a fly,

  • take a moment to marvel at the efficiency of its tiny nervous system

  • as it outsmarts your fancy brain.

The human brain is one of the most sophisticated organs in the world,

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TED-ED】昆虫の脳はなぜすごいのか - Anna Stöckl (【TED-Ed】Why the insect brain is so incredible - Anna Stöckl)

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    Alvin He に公開 2021 年 01 月 14 日
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