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| Percentuali di popolazione locale che possono bere latte (in nero le percentuali più alte: vedi articolo). |
The Neolithic 'milk' revolution.
Fino a circa 8.000 anni fa, a differenza di ciò che accade oggi, gli esseri umani (tutti) erano in grado di digerire il lattosio solo nel periodo post-natale. In età adulta essi perdevano la capacità di produrre la lattasi (l'enzima necessario a digerire il lattosio): questo significa che l'adulto fisiologicamente smetteva di gradire il latte, a seguito di quella che diventava un'intolleranza alimentare fisiologica e normale e non assumeva più latte.
- 1) Il procedimento attraverso il quale si ottengono formaggio e yogurt dal latte riduce efficacemente le quantità di lattosio originalmente contenute nel latte. Questo fatto permise di ottenere un alimento utile, abbastanza tollerabile per tutta la popolazione.
- 2) Poco prima che gli agricoltori allevatori si stanziassero in Europa, comparve - nella popolazione umana - una mutazione genetica che permetteva ai portatori di continuare a produrre la lattasi: si trattava di persone che potevano continuare anche in età adulta a bere il latte e che a maggior ragione potevano assumere qualsiasi latticino senza sintomi d'intolleranza.
Trattandosi di una 'mutazione vantaggiosa', essa si affermò nella popolazione con sorprendente velocità: gli individui che producevano lattasi per tutta la loro vita, pertanto, divennero sempre più numerosi nell'Europa Centrale e Settentrionale.
- I due passaggi segnalati sopra furono proprio uno di quei fattori che permisero agli agricoltori /allevatori di spargersi con successo per tutta l'Europa (il vecchio scenario di scontri bellici e stragi diventa sempre più superato) a svantaggio dei cacciatori/raccoglitori, che avevano abitato per millenni prima quelle stesse regioni.
Riporto di seguito l'articolo in Inglese tratto da una pubblicazione recentissima comparsa su Nature, che riporta studi archeologici a conferma di questi fatti.
Oggi, circa il 60% della popolazione umana è portatrice di quella mutazione e si considera 'normale', mentre il restante 40% si definisce intollerante al latte e si considera in qualche modo malata. La persistenza di lattasi si è sparsa a partire dalle regioni che più probabilmente hanno riguardato la migrazione in Europa degli allevatori: zone in cui si focalizzano gli studi oggi sono l'Anatolia ed il Caucaso.
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| Il percorso seguito nel tempo e nello spazio dalla mutazione 'lattasi persistenza' , ricostruito sulla scorta dei risultati archeologici e genetici: gli studi sono ancora in corso e si focalizzano sul Caucaso e sull'Anatolia, come ipotetiche possibili zone di prima comparsa. |
La distribuzione della mutazione è ineguale, con un massimo nelle zone d'origine ed un minimo nelle aree più distanti: questo è il motivo per cui - per esempio - in Cina essa virtualmente non esiste ed infatti non si consumano né latte né derivati: esiste solo il Tofu, che non è derivato dal latte.
Scientists have brought to light the spread of dairy farming in Europe and the development of milk tolerance in adult humans. It was after the transition from a hunter-gatherer society to that of a settled farming culture in the Neolithic period that dairy-related animal husbandry first evolved, and this practice spread from the Middle East to all of Europe.
The processing of milk to make cheese and yogurt contributed significantly to the development of dairy farming, as this represented a way of reducing the lactose content of fresh milk to tolerable levels, making a valuable foodstuff available to the human population.
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]
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| 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]
