A Natural Example of a Functioning Gear Mechanism Discovered in an Insect

Scientists from the University of Cambridge have discovered a natural example of a functioning gear mechanism in an insect.

Previously believed to be only man-made, a natural example of a functioning gear mechanism has been discovered in a common insect – showing that evolution developed interlocking cogs long before we did.

The juvenile Issus – a plant-hopping insect found in gardens across Europe – has hind-leg joints with curved cog-like strips of opposing ‘teeth’ that intermesh, rotating like mechanical gears to synchronise the animal’s legs when it launches into a jump.

The finding demonstrates that gear mechanisms previously thought to be solely man-made have an evolutionary precedent. Scientists say this is the “first observation of mechanical gearing in a biological structure”.

Through a combination of anatomical analysis and high-speed video capture of normal Issus movements, scientists from the University of Cambridge have been able to reveal these functioning natural gears for the first time. The findings are reported in the latest issue of the journal Science.

The gears in the Issus hind-leg bear remarkable engineering resemblance to those found on every bicycle and inside every car gear-box. Each gear tooth has a rounded corner at the point it connects to the gear strip; a feature identical to man-made gears such as bike gears – essentially a shock-absorbing mechanism to stop teeth from shearing off.

The gear teeth on the opposing hind-legs lock together like those in a car gear-box, ensuring almost complete synchronicity in leg movement – the legs always move within 30 ‘microseconds’ of each other, with one microsecond equal to a millionth of a second.

 A Natural Example of a Functioning Gear Mechanism Discovered in an Insect

An Issus nymph.

This is critical for the powerful jumps that are this insect’s primary mode of transport, as even miniscule discrepancies in synchronization between the velocities of its legs at the point of propulsion would result in “yaw rotation” – causing the Issus to spin hopelessly out of control.

“This precise synchronization would be impossible to achieve through a nervous system, as neural impulses would take far too long for the extraordinarily tight coordination required,” said lead author Professor Malcolm Burrows, from Cambridge’s Department of Zoology.

“By developing mechanical gears, the Issus can just send nerve signals to its muscles to produce roughly the same amount of force – then if one leg starts to propel the jump the gears will interlock, creating absolute synchronicity.

“In Issus, the skeleton is used to solve a complex problem that the brain and nervous system can’t,” said Burrows. “This emphasizes the importance of considering the properties of the skeleton in how movement is produced.”

“We usually think of gears as something that we see in human designed machinery, but we’ve found that that is only because we didn’t look hard enough,” added co-author Gregory Sutton, now at the University of Bristol.

“These gears are not designed; they are evolved – representing high speed and precision machinery evolved for synchronization in the animal world.”

Interestingly, the mechanistic gears are only found in the insect’s juvenile – or ‘nymph’ – stages, and are lost in the final transition to adulthood. These transitions, called ‘molts’, are when animals cast off rigid skin at key points in their development in order to grow.

It’s not yet known why the Issus loses its hind-leg gears on reaching adulthood. The scientists point out that a problem with any gear system is that if one tooth on the gear breaks, the effectiveness of the whole mechanism is damaged. While gear-teeth breakage in nymphs could be repaired in the next molt, any damage in adulthood remains permanent.

It may also be down to the larger size of adults and consequently their ‘trochantera’ – the insect equivalent of the femur or thigh bones. The bigger adult trochantera might allow them to can create enough friction to power the enormous leaps from leaf to leaf without the need for intermeshing gear teeth to drive it, say the scientists.

Each gear strip in the juvenile Issus was around 400 micrometers long and had between 10 to 12 teeth, with both sides of the gear in each leg containing the same number – giving a gearing ratio of 1:1.

Unlike man-made gears, each gear tooth is asymmetrical and curved towards the point where the cogs interlock – as man-made gears need a symmetric shape to work in both rotational directions, whereas the Issus gears are only powering one way to launch the animal forward.

While there are examples of apparently ornamental cogs in the animal kingdom – such as on the shell of the cog wheel turtle or the back of the wheel bug – gears with a functional role either remain elusive or have been rendered defunct by evolution.

The Issus is the first example of a natural cog mechanism with an observable function, say the scientists.

Reference: “Interacting Gears Synchronize Propulsive Leg Movements in a Jumping Insect” by Malcolm Burrows and Gregory Sutton, 13 September 2013, Science.
DOI: 10.1126/science.1240284

Image: Cog wheels connecting the hind legs of the plant hopper, Issus. Credit: Burrows/Sutton

16 Comments on "A Natural Example of a Functioning Gear Mechanism Discovered in an Insect"

  1. Beautiful and elegant.

    I can’t wait for the ID nut cases to jump all over this one!

    • Darwin theory-had-massive-holes | September 13, 2013 at 10:19 am | Reply

      Joy, Not only is Evolution more absurd than scattering the parts of a 747 across the Universe + another 20 billion years, you have a flying 747, but adds the complexity of having no plans for the 747, no parts for the 747, but still getting a flying 747!
      Now who are the nutcases really?

      • I’d say the nutcases are the ones who think that airplane parts are logical comparison to Evolutionary Theory. LEGOs or K’Nex would make far more sense, as the universe has proven to be fairly flexible. Your idea of how evolution works demonstrates your closed mind, as only a 747 could be built in your scenario. There is not just one possible form of life, natural selection molds life into the form it needs to survive in its environment. Not all planes are 747 jetliners, to thrive they need to come in all shapes and sizes.

        Evolution demands a modular approach to the concept of life, not a bunch of pre-fabricated bits that only fit together in one way. Of course, even in that scenario multiple simulations have proven natural selection still functions. https://www.youtube.com/watch?v=mcAq9bmCeR0 shows that with a pile of random parts a clock can in fact be created. So your bogus constraints are just self-defeating.

        • It’s not hard to see how levers evolved in animals and plants. It’s only a further stage for organisms to evolve a kind of gear. We’ve already seen the bacterial flagellum, so we should not be too surprised by the insectile gear. Given that, there is probably nothing inherently impossible in some organism one day evolving the use of the wheel. Perhaps we may even see a caterpillar one day with caterpillar tracks! 🙂

      • Stopping the window lickers | September 15, 2013 at 3:36 am | Reply

        I know that you are trolling but I have to say. Are you really that freekin dim.

  2. Was this a chance discovery or did they meticulously search through all the species of insects for this? Nice discovery though nevertheless.

  3. The article makes it clear how absolutely necessary synchronization is in jumping, thus the gear solution, and expects us to believe this insect type survived millions of years trying to evolve the gear solution? Even if it took only ten years this type of insect would have died out due to inability to move around precisely enough to forage food and evade predators long enough to procreate. It takes more faith to believe in evolution than in God’s ingenuity.

    • There are many insects that haven’t evolved gears. They didn’t die out. Instead they found lifestyles that didn’t require such long leaps. In geared species, the gear (probably a simple 2-toothed variety) would have come first as a mutation which allowed longer leaps and provided a selective advantage.

  4. Why should we stop with insects for this research. Even “ball and socket” joints of humans and knee cap ‘patella’ are a sound proof of mechanical engineering of evolution. Why, even in case of vertebral column, the flexibility achieved for bending by cup model of vertebrae to join with one another with a pin and hole model and the ‘shock absorber’of vertebral discs of sponges in between is a mechanical marvel of evolution. Hats off to the evolution novices . But!!! Is there a thinking mind behind all such things of unknown knowledge, which we suppose to call as ‘God almighty’? Hello! scientists can’t rule out at this stage. Their task is to untie the knots of nature one by one till they reach the apex of all such knots. Thank You.

  5. John 1:3
    All things were made by him; and without him was not any thing made that was made.

    Ecclesiastes 1:9
    That which has been is what will be,
    That which is done is what will be done,
    And there is nothing new under the sun.

  6. Typical of creationists to assume that the organism has to “try” to evolve, rather than adapt to various niches. Typical of a creationist to claim that prior to these gear adaptions the insect would have died. Haven’t they noticed there are trillions of insects without gears? Just like there are billions of four legged mammals, some of which evolved into bipeds. Then again, what am I saying? They think the world began 10,000 years ago. The ridiculous part is that these primitive zealots reap the benefits of a multitude of scientific achievements every day which were made alongside discoveries in evolution and geology, often by the same scientists. We should not have to deal with these people, whose predecessors gave Galileo life imprisonment for claiming the earth was not the center of the universe.

  7. I think the value of cogwheels as a form of efficient motion is overrated. It is more likely that the cogwheels in the Issus insect are used for efficient leverage or angularity, such as creating vertical motion between triangles of grass. Perhaps someone will investigate this.

  8. Cogs are primitive, compared to higher level reflexology. The young Issus is given more time to learn how to conduct intricate flight because the cogs prevent spastic directional outcome. Thus, survival odds are increased, later when the insects reflex actions insure that it can control flight, the cogs have served their purpose. Evolution is Intelligent Design, and visa-versa. Nature, with the exception of Humans, is incapable of Unintelligent Design.

  9. Its typical that an evolutionist cant comprehend there might be something greater than themself. I dont deny that things have evolved, the world is in constant change, but I cant believe this is all be accident.
    If our planet were any further or closer to the sun, it would be uninhabitable. If the earths axis were any different, we wouldn’t have our seasons. If the moon wasn’t positioned were it is, we wouldn’t have the gravity we currently enjoy.
    Just look around at how perfect everything works together. I just cannot believe it was all by chance.

  10. “These gears are not designed they are evolved…” Assumed the supposed unbiased science observer – after explaining how “the gears” are “designed.” This is not a scientific statement of fact but a philosophical statement of belief diguised as science.

    • “These gears are not designed; they are evolved – representing high speed and precision machinery evolved for synchronization in the animal world.”

      True science should not make such a statement, this is assumption of evolution and assumptions should not be made. Just report the facts please as the field supposed to be an “observable discipline”. Please report the findings and the utility and nothing more.


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