TEDxLakeComo – Paolo Ajmone Marsan – 11/04/09

Translator: Michele Gianella
Reviewer: Denise RQ 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. They are chemical basis,
represented as 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,
thus tracking back the evolutionary history of species. DNA forms the chromosomes,
contained in the cell nucleus. A second genome, maybe some of you didn’t know, is in the mitochondria, organelles devoted
to the production of energy. Mitochondrial DNA has a number
of interesting features. Among these is its mode of transmission, only 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 bovine. When did the history of domestic cattle start? 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, 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 the wild ancestor Bos primigenius, a very dangerous animal of extraordinary strength, got domesticated as Bos Taurus, the European type cattle
we see in our farms. Another very important site is Pakistan. The first evidences date back
to 7,000 years BC in the Indo Valley, where they domesticated “Bos Indicus”,
the zebu, the humped cattle now widely spread in South Asia and Africa. Two other possible domestication sites, North Africa and Far East Asia, are still under debate. What information on domestication is contained in cattle mitochondrial DNA? The coloured spheres you see here
represent animals, grouped in geographic areas:
you can see a geographic map and group of spheres in different areas: South West Asia, Anatolia,
Central Europe, Africa, etc. You also see colours. A given colour represents groups of animals having similar
mitochondrial DNA sequence. Different colours indicate animals
with 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 in 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. At each movement, early farmers
moved out of domestication centre at a speed of about 1 Km per year. 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. Each new handful
didn’t contain all the colours 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 repeat: there’s more genetic variation
in South-West Asia and less 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 Central Italy shows
many colours and wide branching, much like South-West Asia. Surprisingly, the Central Italian
explosion of diversity is delimited by “normal” North and South, with the expected red genealogy. We know from archaeological data
that after domestication cattle moved either through the Balkans
and colonized North Europe along the Danube river, or along the Mediterranean coasts. It is possible to calculate distances
between animals comparing DNA letters
and counting how many times the same letter is in the same position, and how many times is in a different one. This so-called genetic distance can also be calculated 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 S-W Asia and Anatolia,
while reds from North and South Italy are close to Central Europe. So, something happened: these animals, surrounded by other “normal ” animals, arrived to Central Italy 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, and both in South and North Italy, high in Central Italy, whose animals look
like those in the domestication centre. They arrived on our shores but they’re
unable to sail by themselves, so somebody must have shipped them. To guess who, we should understand when did these animals
dock to Central Italy. Historical records report on Central Italian bovines. Columella, a Roman expert in Agriculture,
describes them in the I 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, agriculture also 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, it became possible to date the ancestors shared by 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… They arose in Central Italy in the first
millennium BC, exactly in that area. Look, we found a real proof of this… I’m kidding, no scientific journal
would take it as an evidence, however we found an Etruscan fibula representing a Maremmana-like bull, a male one. You see female horns are lyre-shaped, while male ones are crescent-shaped. 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 their period
of highest development is referred to as the Oriental Period-
but they think they’re local. European Experts are divided between local origin
with Eastern influence and purely Eastern origin. Archaeologists have different opinions, as linguists do. We only understand
a few words of their language, and we know the Etruscan alphabet. But no analogous to the Rosetta Stone,
that could allow us to understand Egyptian hieroglyphic,
was ever found. Interestingly, some Etruscan words
seem to have more sense when interpreted according to the Semitic rather than Indo-European languages. Herodotus, in his “Stories”
reports that Etruscans were Lydians, 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 critical in
interpreting our results, we seek advice from re-known human geneticists. And since we were no longer talking about Etruscan cattle, but people, we went to Cavalli Sforza
and his colleagues. Antonio Torroni at that time was working
on human DNA from people living in small villages
of Etruscan heritage. This because people in large cities are probably mixed
and have 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, 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 bovines docked to Tuscany, sailing from S-W Asia. This also confirms how the Italian wisdom “take wife and cattle from your homeplace” is now totally implemented. Since domestication, animals always accompanied humans during migrations, wars and conquers. They have been silent witness
of human history, but until recently they have been
impossible to query. Now, thanks to DNA analysis,
they can tell us their story. Thanks for your attention. (Applause)

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