The Collagua, who lived in the Colca Valley of southeastern Peru, likely modified the heads of babies using bandages or special hats, in order to elongate their heads and create ‘alien-shaped’ skulls.

According to new research, these head-shaping practices may have provided a symbolic basis for the cooperation of elite groups during an era of intense conflict.

However, the class boundaries formed through head-shaping may have contributed to growing social inequality even before the period of the Incan empire’s expansion in South America.

Peruvian elites in the 1100s were easy to spot: they had abnormally elongated skulls.

Important members of the ancient Collagua group in Peru practiced head-shaping, and a stretched, elongated look became a status symbol for elite Collagua.

The Collagua, who lived in the Colca Valley of southeastern Peru, likely modified the heads of babies using bandages or special hats, in order to elongate their heads and create ‘alien-shaped’ skulls.

According to new research, these head-shaping practices may have provided a symbolic basis for the cooperation of elite groups during an era of intense conflict.

However, the class boundaries formed through head-shaping may have contributed to growing social inequality even before the period of the Incan empire’s expansion in South America.

However, historians are still unsure about what happened to the Collagua people and the neighbouring Cavanas people.

Both groups lived during a time of conflict, after the collapse of two prominent Andean societies in 1100, and before the Incan Empire’s expansion at the beginning of the 15th century.

Velasco, who has studied Collagua skull shapes spanning a 300-year period, found that the elongated skulls were increasingly linked with social status.

Velasco studied a total of 211 skulls of mummified humans buried in two Collagua cemeteries, finding evidence of the social status link.

Important members of the ancient Collagua group in Peru practiced head-shaping, and a stretched, elongated look became a status symbol for elite Collagua. The Collagua likely modified the heads of babies using bandages or special hats.

For example, chemical analyses of bones found that women with elongated heads are a wide range of foods.

In addition, Collagua women with stretched skulls were found to have suffered far less skull damage from physical attacks than women who did not have similarly modified skulls.

Until know, most of the knowledge about this practice came from written accounts from Spanish conquistadors in the 1500s.

These documents noted that some Collagua people had tall, thin skulls, while Cavanas had wide, long skulls and may have used wooden planks to do this.

Now, Velasco’s study has widened our knowledge on the nuances of these practices.

The skulls and bones were found in burial structures built against a cliff faces, which were likely only for high-status people.

By contrast, burial areas in caves and under nearby rocky overhangs were for common people.

Radiocarbon analyses of some of the samples enabled Velasco to categorise skulls into early or late pre-Inca groups.

A total of 97 skulls (including 76 from commoner burial areas) belonged to the early group (1150-1300), and 38 of these (39 per cent) had been modified.

Some were elongated, whereas others were modified into wide shapes.

14 of these skulls were elongated, and of these 14, 13 came from low-ranking people, suggesting that common people first started modifying their skulls to elongate them.

However, because only 21 skulls belonging to elite people were found in the early group, it may lead to an underestimate of the early frequency of stretched heads among elite people.

By contrast, among 114 skulls from elite burial areas in the late period (1300-1450) – 84 (74 per cent) had modified shapes, the majority of which where very elongated.

No evidence was found to determine if common people also had elongated skulls in the late period.