“I have been a clinician for 20 years, and only in the last decade, increasingly I have been discovering that my patients have this growth on the skull,” says David Shahar, a health scientist at the University of The Sunshine Coast, Australia.

The spike-like feature, also known as the “external occipital protuberance” is found at the lower back of the skull, just above the neck. If you have one, it’s likely that you will be able to feel it with your fingers – or if you’re bald, it may even be visible from behind.

Until recently, this type of growth was thought to be extremely rare. In 1885, when the spike was first investigated, the renowned French scientist Paul Broca complained that it even had a name at all. “He didn’t like it because he had studied so many specimens, and he hadn’t really seen any which had it.”

Feeling that something might be up, Shahar decided to investigate. Together with his colleague, he analysed over a thousand X-rays of skulls from people ranging from 18 to 86 years old. They measured any spikes and noted what each participant’s posture was like.*

What the scientists found was striking. The spike was far more prevalent than they had expected, and also a lot more common in the youngest age group: one in four people aged 18-30 had the growth. Why could this be? And should we be concerned?

Shahar thinks the spike explosion is down to modern technology, particularly our recent obsession with smartphones and tablets. As we hunch over them, we crane our necks and hold our heads forward. This is problematic, because the average head weighs around 10 pounds (4.5 kg) – about as much as a large watermelon.

Text neck

When we’re sitting upright, these hefty objects are balanced neatly on top of our spines. But as we lean forwards to pore over famous dogs on social media, our necks must strain to hold them in place. Doctors call the pain this can cause “text neck”. Shahar thinks the spikes form because the hunched posture creates extra pressure on the place where the neck muscles attach to the skull – and the body responds by laying down fresh layers of bone. These help the skull to cope with the extra stress, by spreading the weight over a wider area.

Of course, bad posture was not invented in the 21st Century – people have always found something to hunch over. So why didn’t we get the skull protuberances from books? One possibility is down to the sheer amount of time that we currently spend on our phones, versus how long a person would previously have spent reading. For example, even in 1973, well before most modern hand-held distractions were invented, the average American typically read for about two hours each day. In contrast, today people are spending nearly double that time on their phones.

Indeed, for Shahar, the biggest surprise was just how large the spikes were. Before his study, the most recent research was conducted at an osteological lab in India, in 2012. That’s a lab specialising entirely in bones – as you can imagine, they have quite a lot of skulls – but the doctor there only found one with the growth. It measured 8 mm, which is so small, it wouldn’t even have been included in Shahar’s results. “And he thought it was significant enough to write a whole paper about it!” he says. In his own study, the most substantial growths were 30mm long.

Intriguingly, the strong men from the Mariana islands also tend to have growths on their skulls. They are thought to have developed for a similar reason – to support their powerful neck and shoulder muscles. The men may have carried heavy weights by suspending them from poles across their shoulders.

Shahar says it’s likely that the modern spikes will never go away. They will continue to get bigger and bigger – “Imagine if you have stalactites and stalagmites, if no one is bothering them, they will just keep growing” – but it’s rare for them to cause any trouble by themselves. If there is an issue, it will probably be caused by the other compensations that the body must make for all our hunching.