Chichén Itzá is a ruined ancient city occupying an area of 4 square miles (10 square km) in Mexico.
It was originally built by the Maya people around 1,500 years ago.
The site first saw settlers in AD 550, who were likely drawn there due to easy access to water via caves and sinkholes in limestone formations, known as cenotes.
At its peak, Chichén Itzá would have been home to 35,000 people, but it was abandoned in the 15th century.
Source: Encyclopaedia Britannica
The study was led by researchers at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.
Chichén Itzá is one of the New 7 Wonders of the World – but it was once a thriving city, originally built by the Maya people around 1,500 years ago.
Mayans engaged in the brutal act of human sacrifice because they though blood was a potent source of nourishment for their gods – and that they'd get rain and fertile fields in return.
Chichén Itzá is already known for ritual killings, evident from remains of both sacrificed people and art, including 'tzompantli' (stone engravings of skulls).
Back in 1967, remains of more than 100 young children were found in a 'chultun' – a bottle-shaped chamber designed for underground storage – at Chichén Itzá.
Such subterranean features were viewed at the time as connection points to the underworld – the supernatural world of the dead.
For their new study, the researchers performed genetic analysis on remains of 64 of these individuals to reveal their sex.
'When we analyse the genome, there are regions that are part of the Y chromosome, which is found only in male individuals,' study author Rodrigo Barquera at the Max Planck Institute told MailOnline.
'So if we find those regions as part of our genetic data, we can confidently say the sex of that individual is male.'
Until now, there's been a widespread belief among academics that mainly females were sacrificed at Chichén Itzá.
This is largely due to early 20th century accounts that popularized 'lurid tales' of young women and girls as the victims.
But the new genetic analysis unexpectedly shows 'with certainty' that all 64 tested individuals were boys – and includes two pairs of identical twins.
'As such twins occur spontaneously in only 0.4 per cent of the general population, the presence of two sets of identical twins in the chultun is much higher than would be expected by chance,' the authors point out.
In fact, results suggest at least a quarter of the children were closely related to at least one other child in the chultun.
Their 'close biological kinship' could somehow have been thought of by the Mayans as a better offering to the gods.
Twins are especially 'auspicious' in Mayan mythology and twin sacrifice is a central theme in the sacred K’iche’ Mayan Book of Council, the 'Popol Vuh'.
What's more, these young victims – all drawn from local Maya populations – had consumed similar diets, the analysis shows, suggesting they were raised in the same household.
They were likely killed as part of twisted public spectacles before their bodies were placed in the chultun.
Dating of the remains also revealed that the chultun was used for mortuary purposes for more than 500 years, from AD 600 to 1,100.
Most of then were killed and interred during the 200-year period of Chichén Itzá's 'political apex' between AD 800 to 1,000.
Originating around 2600 BC, the Maya civilisation thrived in Central America for nearly 3,000 years, reaching its height between AD 250 to 900.
Noted for the only fully developed written language of the pre-Columbian Americas, the Mayas had advanced art and architecture as well as mathematical and astronomical systems.
But the findings give the greatest insights yet of the poor young victims who died at the hands of their aberrant rituals.
The study – 'Ancient genomes reveal insights into ritual life at Chichén Itzá' – has been published today in the journal Nature.
The Maya civilisation thrived in Central America for nearly 3,000 years, reaching its height between AD 250 to 900.
Noted for the only fully developed written language of the pre-Columbian Americas, the Mayas also had highly advanced art and architecture as well as mathematical and astronomical systems.
During that time, the ancient people built incredible cities using advanced machinery and gained an understanding of astronomy, as well as developing advanced agricultural methods and accurate calendars.
The Maya believed the cosmos shaped their everyday lives and they used astrological cycles to tell when to plant crops and set their calendars.
This has led to theories that the Maya may have chosen to locate their cities in line with the stars.
It is already known that the pyramid at Chichen Itza was built according to the sun’s location during the spring and autumn equinoxes.
When the sun sets on these two days, the pyramid casts a shadow on itself that aligns with a carving of the head of the Mayan serpent god.
The shadow makes the serpent's body so that as the sun sets, the terrifying god appears to slide towards the earth.
Maya influence can be detected from Honduras, Guatemala, and western El Salvador to as far away as central Mexico, more than 1,000km from the Maya area.
The Maya peoples never disappeared. Today their descendants form sizable populations throughout the Maya area.
They maintain a distinctive set of traditions and beliefs that are the result of the merger of pre-Columbian and post-Conquest ideas and cultures.