How did people grow their food 5000 years ago? In search of answers, Brandenburg scientists have travelled through time with the aid of computer simulations and made amazing discoveries.
The people of the Neolithic, who inhabited the
alpine upland between Upper Swabia, Lake Constance and the Swiss Jura mountains
from approximately 4300 BC to 2500 BC, built stilt houses on the shores of
lakes and fens. Their houses were built of wood and clay, offering space for
sleeping and cooking, for hunting and fishing equipment and even for storage.
For their diet, people already kept cows, pigs, sheep and goats, they hunted
game and fish, gathered nuts, berries and mushrooms. During excavations, archaeobotanists
also found traces of cereals, pulses, flax and poppies – testimony to arable
production. But how did they work their fields? Did they use natural
fertilizers, did they pull up weeds, indicating they were gardeners and
farmers, or did they continually decamp, where they would clear or burn down a
new piece of forest and thus obtain fertile land? Scientists from the Swiss
University of Basel have been examining the lives of people in the New Stone
Age (Neolithic) for decades. One of the great unresolved questions: Why did the
people of that time relocate their settlements approximately every 10 to 25
years? Did the fields not yield enough to feed the villagers? In order to find
more precise answers to the »how« of arable farming, the Swiss researchers
approached the Institute for Landscape Systems Analysis of the Leibniz Centre
for Agricultural Landscape Research (ZALF) under the leadership of Dr. Claas
Nendel.
Archaeobotany meets agricultural simulation
The scientists based in
Müncheberg in Brandenburg have specialised in using computer models to simulate
plant growth dependent upon soil, climate, water and nutrients. »We use MONICA
to calculate how climate change could affect the cultivation of wheat, maize or
soya, whether an increase in temperature is positive or negative for crop
yields. We develop models for carbon-efficient methods of cultivation and
advise ministries and associations«, is how Dr. Claas Nendel explains his
team’s work. MONICA is a simulation model developed by the scientists from
ZALF. They are continually testing the program, performing field trials,
feeding the models with data and observing whether the results calculated
correspond to reality.
»So far we have made forecasts with MONICA for the
future of agriculture. But we never made a journey into the past before.« The
scientists at ZALF began to feed MONICA with the data saved by their Swiss
colleagues. The researchers chose emmer, one of the oldest known grains still
occasionally cultivated today, as a study object. As emmer has hardly altered
through cultivation over the millennia, comparisons with today’s plants are
possible. Climate experts confirm that the weather 5000 years ago was similar
to today. The soil on which emmer was cultivated at that time was almost certainly
cleared forest soil. Assuming these basic conditions, the researchers allowed
their computer to play out different scenarios. »We wanted to know how long a
field would have remained fertile.«
The first hypothesis: The people would burn
the future area for cultivation using a »slash-and-burn method«, which brings
very high yields in the short term. They sowed and reaped what grew on the
field – no additional soil management was undertaken. »After one or two
harvests, the soil would have been so poor in nutrients that cultivation would
no longer be worthwhile on these areas and the settlers would have to exploit
new forest areas using slash-and-burn tillage.« The agricultural modellers
calculate that with this method of cultivation, the fields would be continually
moved further from the center of the settlement – after 25 years this would
already be an hour’s walk. »In order to feed themselves, the people would have
to constantly relocate« explains Nendel. There are findings which contradict
this hypothesis, suggesting that only a part of the group of settlers actually
moved. Therefore the researchers investigated a second hypothesis: The fields
were cultivated intensively at that time already, and farmed to achieve a
longer period of use lasting several years at least. »The archaeobotanists
found weeds that only grow on cultivated soils. The people of that time also
fertilized with cow dung. Our calculations show that they did not have enough
dung from their cows to fertilize all the land, but for some of it,« explains
Nendel. After running through various models, the more probable variant
emerged: The people of the alpine upland 5000 years ago were already
strategically thinking farmers.
By using all of the knowledge available to them
– mixed cultivation with peas, fertilization with cow dung, compliance with
fallow periods – they could have lived in one spot for several decades. So
there must have been another reason for their relocation. The results of the
simulations by ZALF are now flowing into the Swiss scientists’ attempts at
reconstruction and are contributing to a reappraisal of the life of the people
from the stilt houses in the Neolithic period and the drawing of new
conclusions about the history of their settlements and agriculture.
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