The Neolithic 'milk' revolution
|Researchers of the BEAN Initial Training Network visiting excavations|
in western Anatolia [Credit: ©: Joachim Burger]
Until 8,000 years ago, humans were only able to digest lactose, a form of sugar present in fresh milk, during childhood because as adults they lost the ability to produce endogenous lactase, the enzyme required to break down lactose.
Shortly before the first farmers settled in Europe, a genetic mutation occurred in humans that resulted in the ability to produce lactase throughout their lives. Increasing numbers of adults in Central and Northern Europe have since been able to drink and digest milk.
"This two-step milk revolution may have been a prime factor in allowing bands of farmers and herders from the south to sweep through Europe and displace the hunter-gatherer cultures that had lived there for millennia," specifies the article in Nature with reference to the LeCHE project.
Since 2009, this EU initial training network involving 12 postgraduate students and their mentors from different disciplines, i.e., anthropology, archaeology, chemistry, and genetics, has been looking at the role played by milk, cheese, and yogurt in the early colonization of Europe and has published numerous important articles on the subject.
Anthropologist Professor Joachim Burger of Johannes Gutenberg University Mainz (JGU) was substantially involved in the establishment of the EU project and its research activities.
"To appreciate the significance of our findings, it is important to realize that a major proportion of present-day central and northern Europeans descend from just a small group of Neolithic farmers who happened to be able to digest fresh milk, even after weaning," explained Burger. His team investigated the phenomenon of lactase persistence, i.e., the ability to break down milk sugar, using skeletons from the Neolithic.
"Among the most exciting results obtained by the LeCHE group were the detection of milk fat residues in numerous Neolithic pottery remains and the ability to model the spread of positive selection of lactase persistence," said Burger.
Just 5,000 years ago, lactase persistence was almost non-existent among populations in which its modern prevalence is greater than 60 percent. The researchers assume that extensive positive selection and recurrent waves of migration were responsible for this development, which -- in evolutionary terms -- took place extremely rapidly.
Burger has now initiated an additional EU project entitled BEAN (Bridging the European and Anatolian Neolithic) to investigate the origins of the first Europeans to settle in the Balkans and western Anatolia. Adam Powell, a mathematician and population geneticist based in London, will be contributing his skills as a modeler and statistician to the team of Mainz anthropologists.
To better understand the actual world in which the early farmers lived, the BEAN researchers recently visited archaeological sites in western Anatolia on a ten-day excursion. "It became very clear to us there that the west of present-day Turkey as well as the Balkans represent two key regions when it comes to the history of the population of Europe over the past 10,000 years," stated Burger.
Source: Universität Mainz [August 28, 2013]