What would you do with a third thumb?

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 IN The University of Cambridge does not think this is quite enough.

Experts have created the ‘Third Finger’ – a controllable prosthesis that attaches to the edge of the right hand.

It allows users to pick up objects, open drink bottles, shuffle 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 “advance 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 true thumb
2. It’s connected to a sensor on the wrist that connects wirelessly to a strap around the ankle
3. Microcontrollers on the ankle strap are connected to pressure sensors under the big toes
4. Pressure from the right finger pulls the prosthetic digit along the hand, and pressure from the left finger pulls it toward the fingers.

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

Although they don’t see a future where humans naturally ‘grow big thumbs’ due to evolution, their robotic version could make people’s lives easier.

It can be especially valuable for amputees who have lost, for example, an arm and have difficulty performing daily tasks with just one hand.

“Our everyday lives are already consumed by wearable technologies and we are now seeing an increasing number of specific augmentation technologies,” study author Lucy Dowdall told MailOnline.

“The third finger can be used to extend the function of the hand – so any task that requires holding many objects at the same time, or stabilizing one item while performing one task with another.”

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

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

Both toe sensors, which are wirelessly connected to the big toe, control various movements by instantly responding to subtle changes in pressure from the toes.

Pressure from the right finger pulls the prosthetic digit across the hand, while pressure from the left finger pulls it toward the fingers, and the released pressure returns it to its original position.

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

The thumb was given in different sizes so that they could fit the hands of children and adults.

Participants performed two tasks – first, they grabbed pins and placed them in a basket, and second, they manipulated and moved five or six different foam objects of different sizes.

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

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

Older and younger adults had a similar level of skill when using the device, although further investigation only within the age group of older adults revealed a decline in performance with increasing age.

“This effect may be due to the general degradation in sensorimotor and cognitive abilities associated with aging,” the team says.

“Furthermore, these effects may also reflect a generational relationship with 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 “could pave the way for setting a standard” for other “immersive” human-centric devices.

“Future growth technologies may have a broad impact on society and benefit many people,” they write.

Scientists reveal how humans ended up with five fingers

A study has identified two genes responsible for the formation of human pectoral and toe rays, which ‘clearly creates a molecular link’ between them.

But the fossil record shows that our ancestors were polydactyls, meaning they had more than five digits per hand, which has left experts wondering why we only have five.

In 2016, researchers discovered that this major morphological change did not occur occur through the addition of new genes, but from a mutation that has occurred within them.

After the earliest hominins—which includes all members of the genus Homo—began walking on two legs about six million years ago, the hand evolved a big toe.

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

This ‘dual movement’ – on the ground, through the trees – remained the norm for another four million years.

As our ancestors abandoned their arboreal shelter, their fingers began to straighten, paving the way for the creation and use of tools.

“Hands were freed from movement in trees so they could be strictly specialized in manipulation,” said researcher Manuel Dominguez-Rodrigo.

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

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