CT scans showing flattening in an Iron Age skull

M.A. Beck De Lotto et al.

Flat head syndrome, commonly associated with modern parenting practices, especially placing babies to sleep on their backs, may have been common at least 2800 years ago.

Because humans are born with soft heads, their skulls can get shaped by pressure. Today’s use of cots and prams tends to create prolonged pressure on the back of the head, which can deform the normally round surface – sometimes for life. The condition is primarily an issue of aesthetics, and isn’t generally considered to affect the brain or cause other symptoms.

Now, an investigation of ancient adult skulls in central Italy suggests that early Iron Age parents may also have placed their babies’ heads against flat surfaces for prolonged periods.

While babies’ heads sometimes get flattened in the womb, many cases of flat head syndrome – also called positional or developmental plagiocephaly – result from long and repeated periods of lying in the same position. Medical attention to the syndrome rose dramatically in the 1990s and early 2000s in the wake of “Back to Sleep” campaigns, designed to help prevent sudden infant death syndrome (SIDS) by having babies sleep on their backs rather than their chests or sides. In a 2018 study in Italy, for example, 38 per cent of infants between 8 and 12 weeks had flat head syndrome.

But the earliest history of developmental plagiocephaly – which appears to be a uniquely human phenomenon – remains unknown. Thus far, researchers have found two plagiocephalic heads in Pakistan dating from 4000 years ago. In Europe, the condition has been identified in 4th-century BC Switzerland and the medieval Czech Republic.

In the new study, Michael Beck De Lotto at Sapienza University of Rome and his colleagues inspected 26 well-preserved skulls from two burial grounds discovered in the 1990s in Matelica, Italy, linked to the Picenes people of the 8th and 9th centuries BC. They found flattened areas on the backs of 11 heads from seven men and four women, making them the earliest known examples of developmental plagiocephaly outside Asia.

For more in-depth analyses, the researchers ran CT scans on the skulls and created 2D and 3D virtual models of each one. None of the skulls showed signs of deformation before birth or after death, meaning it must have occurred in the first year of life before head shape solidified, De Lotto says.

Unlike modern flat head syndrome – which is mostly concentrated across the back of the head – these Iron Age skulls had a variety of flattening patterns, representing different positions. That could be because modern infant-care recommendations are more standardised, says De Lotto.  

While there is no record of childcare practices from this culture, the head shapes suggest parents may have been placing their babies to sleep on their backs with their heads propped up on pillows, he says. They might also have swaddled their babies – as depicted on Roman and Etruscan votive objects – or placed them in cradles.

Even so, the exact mechanisms remain unclear. “The skull alone cannot tell us with certainty whether an infant was tightly swaddled, or was positioned in a particular type of cradle,” he says.

The findings align with an existing “evolutionary mismatch” theory about ancient childcare, says Herbert Renz-Polster, a paediatrician and independent researcher in Germany. As hunter-gatherers moved towards a less mobile lifestyle, he explains, they also transitioned from carrying and co-sleeping with their babies to a “crib and cradle” parenting practice in which babies were placed in bed alone with “sleep aids” like swaddling. That led to babies spending long periods immobile on their backs with extended pressure on their heads.

“The infant skull is a developmental wonder, as it needs to resist gravity, be protective yet flexible, and [be] as lightweight as possible,” says Renz-Polster. “This wonder certainly works well in the expected evolutionary environment where the immature human sleeps in close proximity to the mother and is transported on a human body – influences which all go along with flexible head position and frequent head repositioning. But it must fail when a baby spends most of the day with restricted movements.”

“The idea that everyday sleeping position, swaddling, feeding practices and infant handling may leave skeletal signatures offers a much more intimate glimpse into the lives of children and caregivers in the past,” says Siân Halcrow at the University of Otago, New Zealand, who wasn’t involved in the study.

Another study published this week suggests that two ancient human species, Homo erectus and Homo floresiensis, also had cases of flat head syndrome.