DNA preserved in calcified bacteria on the teeth of ancient human
skeletons has shed light on the health consequences of the evolving diet
and behaviour from the Stone Age to the modern day.
The ancient genetic record reveals the negative changes in oral
bacteria brought about by the dietary shifts as humans became farmers,
and later with the introduction of food manufacturing in the Industrial
Revolution.
An international team, led by the University of Adelaide's Centre for
Ancient DNA (ACAD) where the research was performed, has published the
results in Nature Genetics Febraury 17. Other team members
include the Department of Archaeology at the University of Aberdeen and
the Wellcome Trust Sanger Institute in Cambridge (UK).
"This is the first record of how our evolution over the last 7500
years has impacted the bacteria we carry with us, and the important
health consequences," says study leader Professor Alan Cooper, ACAD
Director.
"Oral bacteria in modern man are markedly less diverse than historic
populations and this is thought to contribute to chronic oral and other
disease in post-industrial lifestyles."
The researchers extracted DNA from tartar (calcified dental plaque)
from 34 prehistoric northern European human skeletons, and traced
changes in the nature of oral bacteria from the last hunter-gatherers,
through the first farmers to the Bronze Age and Medieval times.
"Dental plaque represents the only easily accessible source of
preserved human bacteria," says lead author Dr Christina Adler, who
conducted the research while a PhD student at the University of
Adelaide, now at the University of Sydney.
"Genetic analysis of plaque can create a powerful new record of
dietary impacts, health changes and oral pathogen genomic evolution,
deep into the past."
Professor Cooper says: "The composition of oral bacteria changed
markedly with the introduction of farming, and again around 150 years
ago. With the introduction of processed sugar and flour in the
Industrial Revolution, we can see a dramatically decreased diversity in
our oral bacteria, allowing domination by caries-causing strains. The
modern mouth basically exists in a permanent disease state."
Professor Cooper has been working on the project with archaeologist
and co-Leader Professor Keith Dobney, now at the University of Aberdeen,
for the past 17 years. Professor Dobney says: "I had shown tartar
deposits commonly found on ancient teeth were dense masses of solid
calcified bacteria and food, but couldn't identify the species of
bacteria. Ancient DNA was the obvious answer."
However, the team was not able to sufficiently control background
levels of bacterial contamination until 2007 when ACAD's ultra-clean
laboratories and strict decontamination and authentication protocols
became available. The research team is now expanding its studies through
time, and around the world, including other species such as
Neandertals.
Source: Sciencedaily
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