t all started with a goat. The unfortunate animal was born in the Netherlands in the spring of 1939 – and his prospects did not look good. On the left side of his body, a bare patch of fur marked the spot where his front leg should have been. On the right, his front leg was so deformed, it was more of a stump with a hoof. Walking on all fours was going to be, let’s say, problematic.

But when he was three months old, the little goat was adopted by a veterinary institute and moved to a grassy field. There he quickly improvised his own peculiar style of getting around. Pushing his back feet forwards, he would draw himself up until he was standing half-upright on his hind legs, and jump. The end result was somewhere between the hop of a kangaroo and a hare, though presumably not quite as majestic.

Sadly the plucky goat was involved in an accident soon after his first birthday, and he died. But there was one final surprise lurking in his skeleton.

For centuries, scientists had thought that our bones were fixed – that they grow in a predictable way, according to instructions inherited from our parents. But when a Dutch anatomist investigated the goat’s skeleton, they found that he had begun to adapt. The bones in his hips and legs were thicker than you would expect, while the ones in his ankles had been stretched out. Finally his toes and hips were abnormally angled, to accommodate a more upright posture. The goat’s frame had started to look a lot like those of animals which hop.

Today it’s an established fact that our skeletons are surprisingly malleable. The pure white remains displayed in museums may seem solid and inert, but the bones beneath our flesh are very much alive – they’re actually pink with blood vessels – and they’re constantly being broken down and rebuilt. So although each person’s skeleton develops according to a rough template set out in their DNA, it is then tailored to accommodate the unique stresses of their life.

“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.