Short and inbred prehistoric Maltese: genetics explains decline of temple builders

Scientists in the ancient DNA laboratory in Trinity College Dublin have sequenced the genomes of 4,500-5,000 year-old Maltese humans from Xaghra Circle cave burials.

The findings suggest that without migration and seafaring, Malta’s ancient humans were highly inbred and even shorter than their Neolithic counterparts due to being cut-off on the islands. 

Trinity scientists, along with international colleagues, explored the importance of sea travel in prehistory, by examining the genomes of ancient Maltese humans and comparing these with the genomes of this period from across Europe.

The genetic data seems to have answered why the use of Maltese temples declined towards the end of the third millennium BC: Malta’s ancient humans lacked some of the signatures of genetic changes that swept across Europe in this period, because of their island separation.

Indeed, the sea was a central barrier to genetic exchange. The study, published in the journal Current Biology, finds Malta’s ancient Mediterranean islanders were unusual for their time: an inbred, small, restricted population size due to their genetic isolation.

Researchers’ outstanding finds included the offspring of second-degree relatives, a highly inbred individual uncommon even for ancient times, making this ancient Maltese the second most inbred individual yet detected from the Neolithic world.

The scholars found that ancient Neolithic people from Malta experienced an unusual drop in their size, perhaps because of the deterioration of the local environment and economy.

“Was the sea a barrier or a highway in connecting regions during ancient times? Our research shows that seafaring increased the differentiation between populations from islands and mainland Europe,” said Bruno Ariano, PhD student at Trinity and the first author of the study.

“Thanks to the analysis of hundreds of ancient genomes we discovered a level of structure among populations that correlates with their geographic location. This unprecedented level of resolution will most likely lead to new theories about migration and seafaring.”

The first settlers in the Maltese islands were Neolithic, dated by Queen’s University from the sixth millennium BC.

Maltese culture flourished from 3600 BC with distinctive craft and architecture only found on the islands: one example are the elaborate mortuary structures such as the Xagħra circle in Gozo. This monumentalized, underground tomb yielded the remains of hundreds of individuals and underwent remodelling and enlargement until around 2500 BC when it was abandoned, possibly as part of a wider population decline or replacement.

Prof. Caroline Malone of Queens University Belfast, said prehistoric Maltese builders showed enormous resilience and creativity for over a thousand years, but the new biological evidence demonstrates “that they were also challenged by the maritime distance of their island home”.