What would you do if you had a THIRD thumb? Robotic prosthetics allow people to open bottles, pick up objects, and even peel a banana with one hand

By Jonathan Chadwick for Mailonline

10:24 30 May 2024, updated 10:38 30 May 2024

Human hands have had 10 digits for millions of years.

But it seems that scientists on The University of Cambridge thinks this is not enough.

Experts have created a “Third Thumb” – a controllable prosthetic that attaches to the edge of the right hand.

It allows wearers to lift objects, open drink bottles, deal playing cards, peel a banana and even thread a needle – all with just one hand.

In their study, human volunteers quickly got used to the extra digit – which could “push our motor skills beyond current biological limitations”.

How does it work?

1. The third thumb is worn on the opposite side of the palm to the actual thumb
2. It is connected to a sensor on the wrist that connects wirelessly to the strap around the ankle
3. Microcontrollers in the ankle strap are connected to pressure sensors under the big toes
4. Pressure from the right big toe pulls the prosthetic finger across the hand and pressure from the left big toe pulls it toward the fingers

The study was led by researchers from the MRC Cognition and Brain Science Unit at the University of Cambridge and was published in Science Robotics.

Although they don’t see a future where people naturally ‘develop extra thumbs’ through evolution, a robotic version of them can make people’s lives easier.

This could be particularly valuable for amputees who, for example, have lost an arm and have difficulty performing daily tasks with only one hand.

“Our daily lives are already consumed by wearable technology and we are now seeing an increasing number of purpose-built augmentative technologies,” study author Lucy Dowdall told MailOnline.

“The third thumb can be used to extend the function of the hand – so any task requiring carrying multiple objects at once or stabilizing one object while performing a task with another.”

Designer Dani Clode, a research engineer at UCL’s Plasticity Lab, began developing Third Thumb as part of a postgraduate project at the Royal College of Art.

The third toe is worn on the opposite side of the palm to the person’s actual toe and is controlled by a pressure sensor located under each big toe.

Both finger sensors, which are wirelessly connected to the thumb, control various movements by instantly responding to subtle changes in pressure from the fingers.

Pressure from the right big toe pulls the prosthetic finger across the hand, while pressure from the left big toe pulls it toward the fingers, releasing the pressure to move it back to its original position.

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In their study, the team tested 596 participants between the ages of three and 96, who were given one minute to familiarize themselves with the device.

The thumb came in different sizes to fit the hands of both children and adults.

Participants performed two tasks—first, they collected pegs and placed them in a basket, and second, they manipulated and moved five to six different foam objects of various sizes.

Overall, the thumb was successfully worn and checked by 99.3 percent of the sample, the researchers found.

And 98 percent of participants were able to successfully manipulate objects with their third thumb within the first minute of use.

Older and younger adults had similar levels of ability when using the device, although other research only in the older adults age group revealed a decline in performance with increasing age.

“This effect could be due to the general deterioration of sensorimotor and cognitive abilities that is associated with aging,” the team says.

“Furthermore, these effects could also reflect a generational relationship to technology.”

The thumb is “not commercially available,” and it’s unclear when or how academics might make their device available to the public or how much it would cost.

But they hope it “may pave the way for benchmarking” for more “inclusive” human-centric devices.

“Future augmentation technologies could have a far-reaching impact on society and benefit many people,” they write.

Scientists have revealed how humans ended up with five fingers

The study identified two genes responsible for the formation of fin rays and human fingers, which “clearly establishes a molecular link” between them.

But the fossil record shows that our ancestors were polydactyls, meaning they had more than five digits on their hands, leading experts to wonder why we only have five.

In 2016, researchers found that this major morphological change did not occur they arise from the addition of new genes, but from the mutation that took place in them.

After the first hominins – which include all members of the genus Homo – began walking on two legs six million years ago, the hand developed a longer thumb.

But the fingers remained curved, indicating that the trees remained part of their habitat.

This “dual locomotion”—on the ground, through the trees—remained the norm for the next four million years.

As our ancestors left their wooden perches, their fingers began to straighten, paving the way for the creation and use of tools.

“Hands were freed from movement on trees to become strictly specialized for manipulation,” said researcher Manuel Dominguez-Rodrigo.

“That’s where our discovery fills the gap.”

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