Profile of a mandible from a Southern Italian Neolithic sample (~5.000 BC). Credit: Andrea Quagliariello
During the Neolithic period, human groups around the world shifted from migratory communities of hunter-gatherers to settled groups relying on agriculture. This change happened about 12,000 years ago and is commonly known as the “Neolithic Revolution”.
We know that this agricultural revolution greatly affected dietary habits, narrowing the diversity of food sources and promoting crop derived supplies. But how the dietary shift affected the human oral microbiome is still unclear. Scientists from the University of Padua, in collaboration with Universities of Florence, Rome, Bari and Naples, have analysed 67 dental calculi samples from the Neolithic to Copper Age periods to study the evolution of the ancient oral microbiome, as well as related health conditions1.
“Studying the ancient DNA in these plaques enables us to explain how human microbiomes evolved over time, and shed light on past societies, cultures and life conditions” explains Andrea Quagliariello from the University of Padua, one of the authors.
The Neolithic revolution brought many changes in human lifestyle, from subsistence methods to technology. Previous studies on ancient Neolithic microbiomes have relied on small groups of samples from broad geographical areas. This makes it difficult to separate the impact of ecological and geographical factors from cultural and technological ones. In this study, however, researchers examined a larger sample relative to 76 individuals, collected at various sites in central and southern Italy. The samples cover almost 30,000 years, from 31,000 BC to 2,200 BC. “We integrated dietary and cultural information with genomic data and microscopic analysis” says Quagliariello “learning about taxonomical and functional characteristics of these ancient microbiomes”.
Two previously undescribed shifts in the microbiome composition were discovered. The first one was related to the introduction of an agricultural lifestyle, and resulted in a partial modification of previous oral microbiomes from hunter-gatherers, retaining some of their features. According to the study, this may be because the transition was gradual and region-specific, depending on locally available resources, rather than a drastic change to a homogenous diet.
The second shift happened in the late Neolithic and is probably linked to the disappearance of animal and plant species typical of the hunter-gatherer environments, and to the preference for other food sources derived from farms. Scientists found that, overall, the hunter-gatherer diet was richer in fat and protein, and that hunter-gatherer microbiomes remained very similar even through long periods of time and a possible population replacement.
On the other hand, post-agricultural revolution microbiomes have biochemical and bacterial components derived mainly from carbohydrates and starches, with possible intake of fermented products or milk. This diet change fostered the proliferation of many bacteria that significantly threatened the health of Neolithic farmers.
“I believe that the sample examined is a real game-changer in this regard, as it describes at incredible resolutions the shifts in the human oral microbial composition associated with the change in subsistence strategies and dietary habits,” says Claudio Ottoni from the University of Rome, Tor Vergata, who was not involved in the study.
