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TEDxLakeComo 2009 - Paolo Ajmone Marsan

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Good evening, ladies and gentlemen, tonight we’ll travel in time to shed light on an interesting event of past human history. We’ll use a biological time machine: cattle DNA. The DNA is the code of life. It contains all the information needed for the correct functioning of living organisms. Geneticists represent it as an alphabet, with four letters. These letters and the associated code are transmitted from parents to progeny, across generations. The DNA duplication machinery is not error free. Letters may be mistyped and errors transmitted to progeny. These mutations create the genetic variation that is at the row material shaped by evolution and speciation. Some of these errors have dramatic consequences and cause severe diseases. The investigation of these errors also permits the reconstruction of genealogies, in humans as well as in animals, and to reconstruct the evolutionary history of species. DNA forms the chromosomes, contained in the cell nucleus. A second genome is present in mitochondria, organelles devoted to the production of energy. Mitochondrial DNA has a number of interesting features. Among these is its mode of transmission, along the maternal lineage, from mother to progeny. Hence, the investigation of mitochondrial DNA variants permits to reconstruct the “female history” of species. Let’s go back to bovines. The history of domestic cattle started with domestication, at the onset of agriculture, about 10,000 years ago. Agriculture marked the beginning of a new era, the Neolithic, and represented a fundamental step in the evolution of modern society by fostering the conversion of hunter-gatherers into farmers. Farmers created stable settlements. Stability and food availability permitted a demographic expansion of human populations and their stratification in classes, most having occupations other than food hunting, the seed of complex modern societies. Archaeological and archaeobiological records indicate the existence of two and perhaps four sites of cattle domestication. The most ancient site is in the Fertile Crescent, dated about 8,500 years BC, in an area at the border of Iran, Iraq and Turkey. Here Bos Taurus, the European type cattle we see in our farms, was domesticated from the wild ancestor Bos primigenius, a very dangerous animal of extraordinary strength. The second main site is in Pakistan, along the Indo river valley. Bos indicus, the zebu, was domesticated here about 7,000 years BC. The zebu is the humped cattle widely diffused in South Asia and Africa. Two other possible domestication sites in North Africa and Far East Asia are presently under debate. What information on domestication is contained in cattle mitochondrial DNA? The spheres you see here represent animals that are grouped in geographic areas. You can see a geographic map and group of spheres in South West Asia, Anatolia, Central Europe, Africa, etc. You also see colours. A same colour represents groups of animals having similar mitochondrial DNA sequence. Different colours indicate animals having different mitochondrial sequences. Colours indicate genealogies. The reds are a large family, the yellows another large family and so on. Branches of spheres are present within colours, indicating the existence of variants also within genealogies, the wider the branching, the greater the variability of mitochondrial DNA sequences within a family. How can these pattern be interpreted? In Anatolia and South-West Asia the genetic variability is higher than in Europe and Africa. You may see the presence of all colours and wide branching here. In Europe this variability decreases and almost all animals possess red variants of the mitochondrial DNA, while in Africa the yellow family predominates. Why variability was lost? The variability captured with domestication was lost during Europe and Africa colonization. The expansion of Agriculture occurred through serial short range migrations. Let’s imagine the genetic variability captured by domestication as a bowl of spheres of different colours. Early farmers moved out of domestication centre at a speed of about 1 Km per year. At each movement they were taking a handful of spheres, that is animals, funding a new settlement and then multiplying spheres in a new bowl. Following demographic expansion, the progeny of the farmers moved again, taking a handful of spheres from the second bowl. This pattern repeated from generation to generation. Each new handful didn’t contain all colours present in the previous bowl and this caused a gradual loss of variability. Hence mitochondrial DNA agrees with archaeological and archaeobiological data and indicates a cattle domestication in South-West Asia, where the highest variation is observed. Let’s use a magnifying lens on Italy now. I remind you that we observe a high genetic variation in South-West Asia and a low variability in Europe. In Italy the pattern of cattle diversity is quite strange. In Southern and Northern Italy patterns are very similar to Central Europe, while many colours and wide branching are present in Central Italy, a pattern resembling that of South-West Asia. Surprisingly, the Central Italian explosion of diversity is delimited in the North and in the South by Europe-like low diversity patterns of the expected red genealogy. We know from archaeobiological data that after domestication cattle moved through the Balkans and colonized Europe Northward along the Danube river, and Westward along the Mediterranean coasts. It is possible to calculate distances between animals comparing DNA letters and counting how many of them are different. Genetic distance can be calculated also between groups of animals. Genetic distances between maternal DNAs confirm what previously suggested by diversity patterns. North and South Italy are close to Central Europe, while Central Italy is closer to South West Asia and Anatolia. Even for the European red genealogy cattle from Central Italy are closer to South Western Asia and Anatolia, while reds from Northern and Southern Italy are close to Central Europe. So, something happened. These animals, surrounded by animals carrying European-type mitochondrial DNA, arrived to Central Italy arrived from the sea rather than via the land route. Let me introduce you these breeds. The first one is Maremmana, here you may see a female, with typical lyre shape horns. Males have crescent-shaped horns. The Chianina, the largest cattle in the world. The famous sire Donetto reached a weight of over 1700 kilograms. American colleagues get mad, since we hold this primacy... Calvana, a beef breed and Cabannina, a small size dairy breed. What happened then? We have high diversity in South West Asia, low in Europe, low in South and North Italy, high in Central Italy, with Central Italian Animals similar to those in the domestication centre. These animals arrived via the sea route but, since they were unable to sail by themselves, somebody must have shipped them. To guess who, we should understand when these animals docked to Central Italy. Historical records report on Central Italian bovines. Columella, a Roman author expert in Agriculture, describes Central Italian bovines in the first century BC. Other fonts report that even before the Roman king Numa Pompilio used to offer huge white bovines to gods in religious ceremonies. Hence, these animals were in Central Italy before Roman times. However, also agriculture arrived to Italy way before Romans. In fact, the Neolithization of Italy occurred about 6000 years BC. How to narrow down the arrival period of these cattle? Mitochondrial DNA, our time machine, helps also in this case. By reconstructing genealogies and knowing DNA mutation rate, was it possible to date ancestors common to modern Central Italian and South West Asian cattle. These ancestors lived in South West Asia and a branch of their progeny moved to Tuscany. The molecular clock dated their arrival around 2,000 BC. So we have some evidence on a possible relationship with the Etruscans: geography, date, the sea route... This civilization arose in Central Italy in the first millennium BC exactly in that geographic area. Look, we found a real proof of this…… I’m kidding, no scientific journal would obviously accept this as an evidence, however we found an Etruscan fibula representing a bull resembling Maremmana bulls, you may recall that females have horns having a lyre shape. These are bulls, with crescent-shaped horns. The origin of Etruscan civilization is still debated. The Italian school supports the local origin of Etruscans even if a clear influence from Eastern culture is acknowledged, so that the period of highest development of this civilization is referred to as the Oriental Period. European Experts are divided between Eastern origin and local origin with Eastern influence. Archaeologists have different opinions, as linguists do. We know the Etruscan alphabet but we only understand a few words of their language. No analogous to the Rosetta Stone, that permitted to understand Egyptian geroglyphic, was ever found. Interestingly some Etruscan words appear to have more sense when interpreted according to the Semitic rather than Indo-European languages. Herodotus, in his “Stories” reports that Etruscans were Lidians, once settled on the coast of modern Turkey, that sailed to Tuscany and funded the Etruscan civilization. Human genetics for a long time have produced inconclusive results. Etruscan bones have been analysed. The results indicate modern Tuscans as the closest population to Etruscans and Anatolians just a little further. Since Etruscans were of primary importance in the interpretation of our results, we seeked advice from reknown human geneticists, We went to Cavalli Sforza and his colleagues. Antonio Torroni at that time was investigating mitochondrial DNA from human populations living in small villages of Etruscan heritage. This because people in large cities is probably mixed and has excessively diluted DNA signatures of ancient origin. The end of the story is that we joined bovine and human evidence. You may see on the right side Casentino and Murlo, two small villages once Etruscan settlements, both closer to South West Asia than to Europe, while in Volterra this ancient signal is now too diluted to be detected. Human and bovine mitochondrial DNAs indicate that Etruscans and Central Italian bovines docked together to Tuscany, sailing from South West Asia. This also confirms the wisdom of the traditional proverb “take wife and cattle from your homeplace”.... Since domestication, animals always accompanied humans during migrations, wars and conquers. They have been silent witness of human history and until recently they have been impossible to interrogate. Now, thanks to DNA analysis, they answer our questions. Thanks for your attention. (Applause)

Video Details

Duration: 18 minutes and 6 seconds
Country: Italy
Language: Italian
Producer: TEDx
Director: Gerolamo Saibene
Views: 302
Posted by: tradottiinitaliano on Dec 12, 2010

Divide la sua vita professionale fra insegnamento universitario e ricerca sulla genetica di piante e animali. Ha iniziato la sua esperienza nella Silicon Valley, in California, presso Escagenetic Corporation, dove ha lavorato sulla moltiplicazione in vitro di piante da frutto. Tornato in Italia, ha lavorato sul mais ed è stato tra i primi al mondo a identificare componenti del suo genoma contenenti i geni utili per aumentare la produzione. Dal 1997 lavora alla Facoltà di Agraria dell’ Università Cattolica del S. Cuore, dove dirige il laboratorio di biotecnologie animali e il Centro di Ricerca sulla Biodiversità e sul DNA antico.

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