Climate drove 7,000 years of dietary changes in the Central Andes
Only under the Inca Empire did sociopolitical factors dampen local
climate's influence on diet

Date:
February 9, 2022
Source:
University of Utah
Summary:
What a person eats influences a person's health, longevity and
experience in the world. Identifying the factors that determine
people's diets is important to answer the bigger questions, such
as how changing climates will influence unequal access to preferred
foods. A new study provides a blueprint to systematically untangle
and evaluate the power of both climate and population size on the
varied diets across a region in the past.



FULL STORY ==========================================================================
What a person eats influences a person's health, longevity and experience
in the world. Identifying the factors that determine people's diets is important to answer the bigger questions, such as how changing climates
will influence unequal access to preferred foods.


==========================================================================
A new study led by University of Utah anthropologists provides a blueprint
to systematically untangle and evaluate the power of both climate and population size on the varied diets across a region in the past.

The authors documented that climate had the most influence over diet in
the Central Andes between 400 and 7,000 years ago. This makes sense --
the climate determines what resources are available for people in the
area. The researchers were surprised that population size had little
impact on diet variation, despite many complex societies emerging at
various points over time that would have brought disparate communities together, fostered trade and increased competition.

The exception was during the Late Horizon (~480-418 yBP), when diets
across the region became more similar to one another. This coincides
with the Inca Empire that appears to have centralized enough political
power to reduce local dietary decisions, and therby dampen influence
of climate. The study presents a framework for exploring the relative
role of climate and other socio- demographic factors on dietary change
through time -- including in the future.

"Given the rapid climate changes happening in the world today, our study suggests that projected climactic changes will be essential to predict
health and well-being for populations in the future," said Kurt Wilson,
lead author and doctoral researcher at the U.

The study published on Monday, Feb. 7, 2022 in the journal Scientific
Reports.

The Central Andes' breathtaking terrain spans from sea level to some
of the world's tallest mountains. At each elevation, the climate and
food resources are wildly different. Coastal communities relied mainly
on marine resources, with some agriculture. Mid-elevation societies
had access to some marine resources and raised pastoral animals such as
llamas, but mainly relied on agriculture. High elevation diets consisted
of some agriculture but were dominated by pastoral animals.



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The region's demographic history undulates as wildly as the landscape,
with complex societies rising and falling at various points in
time. Changes in population size can influence sociopolitical complexity
or alter mobility patterns, both of which will influence diets.

"I am really interested in the emergence of material inequality. If
you have people eating different things based on status, there's your inequality," Wilson said. "I couldn't compare status and inequality
directly with the data that was available. So, we asked, 'How can we approximate what amount of influence sociopolitical complexity might
have on food availability?'" To do so, the authors compiled the largest dataset of past diets based on carbon (?13C 0/00) and nitrogen (?15N 0/00) isotopic values in the Americas over the last 7,000 years. Derived from
a person's bone collagen, the stable isotopes represent an individual's lifetime average diet and how much was made up of different broad
categories of plant (carbon) and animal (nitrogen) sources.

Using publicly available data, the researchers identified 1,767
individuals from published literature in Peruvian, northern Chilean and
Lake Titicaca archaeological sites. For each individual's location,
they generated variation of local climates using model simulations
of mean annual precipitation, mean annual temperatures, mean annual
seasonal temperatures and mean annual precipitation seasonality. They
also generated population size estimates for each individual using a
"dates as data" approach with a compilation of ~4,000 radiocarbon dates
by treating the number of dated sites at any one time as a proxy for
the relative population size.

"It's a pretty remarkable dataset that represents untold hours of
research generated by archaeologists over decades," said Brian Codding, associate professor of anthropology at the U and last author of the
study. Wilson led a team of undergraduate researchers, all co-authors,
to help compile these findings. "Pulling it all together, and making
it accessible, is a great example of where archaeology is headed, to
answer big questions and to make the science open and reproducible."
They compared dietary trends over time, across three elevation categories: coastal, mid-elevation and highland. This allowed them to capture how
much of diet is explained by population change and local climate, which estimates how much might be due to other social factors.



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The findings showed little dietary overlap between region in the carbon
and nitrogen isotopes for most of the 7,000 years of the study. However,
most of that variation collapses at the Late Horizon (~480 -- 418 yBP),
when the Inca Empire dominated the region.

In the Middle Horizon (~1,350 -- 950 yBP), also a period with political centralization, there's an overlap in carbon for coastal and mid-elevation individuals. During this period, both the Tiwanaku and Wari Empires
engaged in regional trade and resettlement, and contributed to expanding
maize as an important feasting component. Yet nitrogen signatures
remained distinct in elevation zones, suggesting environment continued
to dominate diet.

"Even when we're centralizing politically, people are still heavily
reliant on what's local to them. Then in the Late Horizon, the data
strongly suggest that all of a sudden, this disappears," said Wilson. "The influence exerted by the Inca Empire overrode local climate influences
on diet in ways the Wari and Tiwanaku Empires could not." This research details how most of the differences between peoples' diets, a key part
of daily life, in the Central Andes resulted from different climates. It
also suggests that in the most socio-politically, interconnected period,
social processes may override climatic effect. Next, the authors will
add data on the amount of sociopolitical influence that each individual
may have experienced, which may unveil unseen patterns in how inequality interacted with climate to impact daily life.

Researchers can apply these methods to other regions to identify how
much climate and population changes altered the diets of people over
human history.

"What people eat, and how they get it, are a massive part of a person's
daily experience," Wilson said. "Understanding what caused changes in
those behaviors in the past is important to understanding how we may
respond to changes in the future." Co-authors of the study include
Weston McCool, Simon Brewer, Nicole Zamora- Wilson, Percy Schryver,
Roxanne Lois Lamson, Ashlyn Huggard, and Joan Brenner Coltrain of the University of Utah; and Daniel Contreras of the University of Florida.

========================================================================== Story Source: Materials provided by University_of_Utah. Original written
by Lisa Potter.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Kurt M. Wilson, Weston C. McCool, Simon C. Brewer, Nicole
Zamora-Wilson,
Percy J. Schryver, Roxanne Lois F. Lamson, Ashlyn M. Huggard, Joan
Brenner Coltrain, Daniel A. Contreras, Brian F. Codding. Climate and
demography drive 7000 years of dietary change in the Central Andes.

Scientific Reports, 2022; 12 (1) DOI: 10.1038/s41598-022-05774-y ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220209154937.htm

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