Archaeological study of 24 ancient Mexican cities reveals that collective forms of governance, infrastructural investments, and collaboration all help societies last longer

 Some cities only last a century or two, while others last for a thousand years or more. Often, there aren’t clear records left behind to explain why. Instead, archaeologists piece together clues from the cities’ remains to search for patterns that help account for why certain places retained their importance longer than others. In a new study published in the journal Frontiers in Ecology and Evolution, researchers examined 24 ancient cities in what’s now Mexico and found that the cities that lasted the longest showed indications of collective forms of governance, infrastructural investments, and cooperation between households.

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The shared central plaza of Monte Alban, a city that lasted for more than 1,300 years.

CREDIT

Photo by Linda M. Nicholas

“For years, my colleagues and I have investigated why and how certain cities maintain their importance or collapse,” says Gary Feinman, the study’s lead author and MacArthur Curator of Anthropology at the Field Museum in Chicago.

In previous studies, Feinman and his colleagues cast a wide net in terms of the cities they looked at, ranging across Mesoamerica over thousands of years. They found a broad pattern of societies with good governance that fostered the well-being of their people lasting longer than ones with autocratic leaders and big disparities in wealth. This new study tightens the focus on cities from similar places and times: all 24 of the cities analyzed were in the western half of Mesoamerica and were founded between 1000 and 300 BCE.

To a non-archaeologist, looking at ancient ruins and trying to extrapolate what its government was like might seem like an impossible task. But remnants of the cities’ buildings, ground plans, plazas, and monuments contain clues.

“We looked at public architecture, we looked at the nature of the economy and what sustained the cities. We looked at the signs of rulership, whether they seem to be heavily personalized or not,” said Feinman. Art and architecture celebrating larger-than-life rulers point to more autocratic or despotic societies, whereas the depiction of leaders in groups, often masked, is more indicative of shared power arrangements.

Feinman and his co-authors, David Carballo of Boston University, Linda Nicholas of the Field Museum, and Stephen Kowalewski of the University of Georgia, found that among the 24 ancient cities they analyzed, the ones with more collective forms of governance tended to remain in power longer than the autocratically ruled cities, sometimes by a thousand years. However, even among places that likely had good governance, some cities outlasted others.

To get at why these similarly governed cities fared differently, the researchers examined other aspects of their makeup including infrastructure and indications of household interdependence. “We looked for evidence of path dependence, which basically means the actions or investments that people make that later end up constraining or fostering how they respond to subsequent hazards or challenges,” says Feinman.

Early efforts to construct dense, interconnected residential spaces and the construction of large, central, open plazas were two of the factors that the authors found contributed to greater sustainability and importance of the early cities.

To examine sustainability in the past, most research looks for correlations between specific climatic or environmental events and the human responses. This approach may make sense, but it is hard to know whether the timing is reliable. Such studies often emphasize a correlation between environmental crisis and collapse without also considering how other cities successfully navigated the challenges and continued as major population centers.

The authors use a different tack. Knowing residents faced hazards, including drought, earthquakes, periodic hurricanes/heavy rains, challenges from competing centers and groups, they examined the durational history of the 24 centers and what factors fostered their sustainability. The finding that governance had an important role in sustainability shows that “responses to crises and disasters are to a degree political,” says Linda Nicholas, an adjunct curator at the Field Museum and co-author of the study.

The cities that lasted the longest had a combination of infrastructural investments and collective governance. It’s a lesson still relevant today. “You cannot evaluate responses to catastrophes like earthquakes, or threats like climatic change, without considering governance,” says Feinman. “The past is an incredible resource to understand how to address contemporary issues.”

 

The world’s first horse riders

 

 

IMAGE: GRAVE OF A HORSE RIDER DISCOVERED IN MALOMIROVO, BULGARIA view more 

CREDIT: MICHAŁ PODSIADŁO

The researchers discovered evidence of horse riding by studying the remains of human skeletons found in burial mounds called kurgans, which were between 4500-5000 years old. The earthen burial mounds belonged to the Yamnaya culture. The Yamnayans had migrated from the Pontic-Caspian steppes to find greener pastures in today´s countries of Romania and Bulgaria up to Hungary and Serbia.

Yamnayans were mobile cattle and sheep herders, now believed to be on horseback.

“Horseback-riding seems to have evolved not long after the presumed domestication of horses in the western Eurasian steppes during the fourth millennium BCE. It was already rather common in members of the Yamnaya culture between 3000 and 2500 BCE”, says Volker Heyd, Professor of Archaeology at the University of Helsinki and a member of the international team, which made the discovery.

These regions west of the Black Sea constitute a contact zone where mobile groups of herdsmen from the Yamnaya culture first encountered the long-established farmer communities of Late Neolithic and Chalcolithic traditions. For decades, the Early Bronze Age expansion of steppe people into southeastern Europe was explained as a violent invasion.

With the advent of ancient DNA research, the differences between these migrants from the east and members of local societies became even more pronounced.

“Our research is now beginning to provide a more nuanced picture of their interactions. For example, findings of physical violence as were expected are practically non-existent in the skeletal record so far. We also start understanding the complex exchange processes in material culture and burial customs between newcomers and locals in the 200 years after their first contact”, explains Bianca Preda-Bălănică, another team member from the University of Helsinki. 

Horse riding is a pivotal moment in human history

The use of animals for transport, in particular the horse, marked a turning point in human history. The considerable gain in mobility and distance had profound effects on land use, trade, and warfare. Current research has mostly focused on the horses themselves. However, horse-riding is an interaction of two components – the mount and its rider – and human remains are available in larger numbers and more complete condition than early horse remains. Since horseback riding is possible without specialized equipment, the absence of archaeological finds with regard to earliest horsemanship does not come unexpected.

Traces of horsemanship can be found in the skeletons

“We studied over 217 skeletons from 39 sites of which about 150 found in the burial mounds belong to the Yamnayans. Diagnosing activity patterns in human skeletons is not unambiguously. There are no singular traits that indicate a certain occupation or behavior. Only in their combination, as a syndrome, symptoms provide reliable insights to understand habitual activities of the past.”, explains Martin Trautmann, Bioanthropologist in Helsinki and the lead author of the study.

The international team decided to use a set of six diagnostic criteria established as indicators of riding activity (the so-called “horsemanship syndrome”):

1. Muscle attachment sites on pelvis and thigh bone (femur);

2. Changes in the normally round shape of the hip sockets;

3. Imprint marks caused by pressure of the acetabular rim on the neck of the femur;

4. The diameter and form of the femur shaft;

5. Vertebral degeneration caused by repeated vertical impact;

6. Traumata that typically can be caused by falls, kicks or bites from horses.

To increase the diagnostic reliability, the team also used a stricter filtering method and developed a scoring system that takes into account the diagnostic value, distinctiveness and reliability of each symptom. Altogether, out of the 156 adult individuals of the total sample at least 24 (15.4%) can be classified as 'possible riders', while five Yamnaya and two later as well as two possibly earlier individuals qualify as 'highly probable riders'. “The rather high prevalence of these traits in the skeleton record, especially with respect to the overall limited completeness, show that these people were horse riding regularly”, Trautmann states.

If the primary use of horseback riding was as a convenience in a mobile pastoral lifestyle, in allowing a more effective herding of cattle, as means of swift and far-ranging raids or just as symbol of status needs further research.

Could it all have happened even earlier?

“We have one intriguing burial in the series” remarks David Anthony, emeritus Professor of Hartwick College USA and also senior co-author in the study.

“A grave dated about 4300 BCE at Csongrad-Kettöshalom in Hungary, long suspected from its pose and artifacts to have been an immigrant from the steppes, surprisingly showed four of the six riding pathologies, possibly indicating riding a millennium earlier than Yamnaya. An isolated case cannot support a firm conclusion, but in Neolithic cemeteries of this era in the steppes, horse remains were occasionally placed in human graves with those of cattle and sheep, and stone maces were carved into the shape of horse heads. Clearly, we need to apply this method to even older collections.”

 

 

Short fact box: Who were the Yamnayans?

The Yamnayans were a population and culture that evolved in the Pontic-Caspian steppes at the end of the fourth millennium BCE.

By adopting the key innovation wheel and wagon, they were able to greatly enhance their mobility and exploit a huge energy resource otherwise out of reach, the sea of steppe grass away from the rivers, enabling them to keep large herds of cattle and sheep. Thus committing to a new way-of-life, these pastoralists if not first true nomads in the world expanded dramatically within the next two centuries to cover more than 5000 kilometers between Hungary in west and, in form of the so-called Afanasievo culture, Mongolia and western China in the east. Having buried their dead in grave pits under big mounds, called kurgans, the Yamnayans are said to be the first having spread proto-Indo-European languages.

More information on the research:

https://www.helsinki.fi/en/researchgroups/the-yamnaya-impact-on-prehistoric-europe

Israel: the origin of the world's grapevines

A recent study on the genetic makeup of grapevine has revealed fascinating insights into its domestication and evolution. The study, published in the journal Science, suggests that the harsh climate during the Pleistocene era resulted in the fragmentation of wild ecotypes, which paved the way for the domestication of grapevine about 11,000 years ago in the Near East (Israel) and the Caucasus.

The research team sequenced the genomes of 3525 grapevine accessions (2503 V. vinifera (domesticated) and 1022 V. sylvestris (wild) accessions of grapevine, to identify the genetic changes that occurred during domestication and evolution of grapevine in Euro-Asia.

According to the study, the Near East (Israel) wild grapevine population (Syl-E1) is the source for the domestication of table grapes, which then dispersed into Europe with early farmers, introgressed with ancient wild western ecotypes, and diversified into unique western wine grape ancestries by the late Neolithic.

Furthermore, the study shows that hybridization with local V. sylvestris was common in creating extant European wine grapes. However- when these introgression events occurred, remain unknown.

Dr Elyashiv Drori, Head of the Samson Family Grape and Wine Research Centre at Ariel University and Eastern Regional R&D Center says, "Our findings provide important insights into the domestication and evolution of grapevine, which is a religiously, culturally and economically important crop.

The indigenous grapevine population we have collected in the last 12 years, containing both wild and domesticated subpopulations, have central importance in this research. The Israeli wild grapevines (Syl -E1) were found to be the source of domestication for all the cultivated group of table grapes (CG1), which includes the Israeli domesticated grapevines. This initial group of grapevine varieties then were dispersed to eastern and western Europe, to form most of the known winegrapes.  We now aim to deeply study the characteristics of Israel's indigenous grapevine, which were developed in the dry and harsh conditions of the Levant, and may pose a repository for resistance genes.

With climate change and emerging diseases threatening vineyards worldwide, the study's findings may help in developing new strategies to protect and sustain the wine industry for future generations.

Prof Ehud Weiss, head of the archaeobotanical lab at Martin (Szuss) Department of Land of Israel, Bar Ilan University, a specialist in the domestication of crops and archaeobotany, gave important insights as to the domestication history. Prof Weiss adds "this is a research breakthrough in the field of the beginning of agriculture as well. The accepted view was that annual crops, like wheat, barley, and legumes, were domesticated some 10,000 years ago, while perennials were domesticated thousands of years later. Current research changes this view and demonstrates these transitions occurred simultaneously, and moreover, with the same species, some 1,600 kilometers apart – a phenomenon we have never met."

Two Israeli scientists collaborated with Dr. Drori's team in this project. Prof Ehud Weiss collaborated with Dr. Drori to identify the varieties used by ancestors in the land of Israel using genetic and morphological tools. Dr. Sariel Hubner from Migal is a bioinformatician. Dr. Hubner is working with Dr. Drori's group on the population genetics of the Israeli wild and domesticated grapevines. This collaborative research group published the first research paper describing the possible local domestication of grapevine in Israel in 2021 (Sivan 2021). 

This is a ground-breaking study also in the field of the beginnings of agriculture. This is the first research proof that the domestication of a perennial plant happened at the same time as the domestication of annuals, wheat, barley, legumes, and flax. Until today, it was common to say that fruit trees were domesticated several thousand years later. In addition, the double domestication of the same species into two varieties, in our case the edible grape variety and the wine grape variety, happened at the same time in two separate geographical centers - a phenomenon we had not known until now.

Ice Age survivors

 

Large-scale genomic analysis documents the migrations of Ice Age hunter-gatherers over a period of 30,000 years – they took shelter in Western Europe but died out on the Italian peninsula

Peer-Reviewed Publication

MAX PLANCK INSTITUTE FOR EVOLUTIONARY ANTHROPOLOGY

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IMAGE: RECONSTRUCTION OF A HUNTER-GATHERER ASSOCIATED WITH THE GRAVETTIAN CULTURE (32,000-24,000 YEARS AGO), INSPIRED BY THE ARCHAEOLOGICAL FINDINGS AT THE ARENE CANDIDE SITE (ITALY). view more 

CREDIT: TOM BJOERKLUND

The team analysed the genomes of 356 prehistoric hunter gatherers from different archaeological cultures – including new data sets of 116 individuals from 14 different European and Central Asian countries. Modern humans began to spread across Eurasia around 45,000 years ago but previous research showed that the first modern humans that arrived in Europe did not contribute to later populations. This study focuses on the people who lived between 35,000 and 5,000 years ago and that are, at least partially, the ancestors of the present-day population of Western Eurasia, including – for the first time – the genomes of people who lived during the Last Glacial Maximum (LGM), the coldest phase of the last Ice Age, around 25,000 years ago.

Climatic refugium or dead end?

Surprisingly, the research team found that populations from different regions associated with the Gravettian culture, which was widespread across the European continent between 32,000 and 24,000 years ago, were not closely related to each other. They were linked by a common archaeological culture: they used similar weapons and produced similar portable art. Genetically, however, the populations from western and southwestern Europe (today's France and Iberia) differed from contemporaneous populations from central and southern Europe (today's Czech Republic and Italy).

Furthermore, the gene pool of the western Gravettian populations is found continuously for at least 20,000 years: their descendants who are associated with the Solutrean and Magdalenian cultures stayed in southwestern Europe during the coldest period of the last Ice Age (between 25,000 and 19,000 years ago) and later spread north-eastward to the rest of Europe. "With these findings, we can for the first time directly support the hypothesis that during the Last Glacial Maximum people found refuge in the climatically more favourable region of southwestern Europe" says first author Cosimo Posth.

The Italian peninsula was previously considered to be another climatic refugium for humans during the LGM. However, the research team found no evidence for this, on the contrary: hunter-gatherer populations associated with the Gravettian culture and living in central and southern Europe are no longer genetically detectable after the LGM. People with a new gene pool settled in these areas, instead. "We find that individuals associated with a later culture, the Epigravettian, are genetically distinct from the area‘s previous inhabitants," says co-author He Yu. "Presumably, these people came from the Balkans, arrived first in northern Italy around the time of the glacial maximum and spread all the way south to Sicily." 

Large-scale genetic replacement

The analysed genomes also show that the descendants of these Epigravettian inhabitants of the Italian peninsula spread across the rest of Europe about 14,000 years ago, replacing populations associated with the Magdalenian culture. The research team describes a large-scale genetic replacement that may have been caused, in part, by climatic changes that forced people to migrate: "At that time, the climate warmed up quickly and considerably and forests spread across the European continent. This may have prompted people from the south to expand their habitat. The previous inhabitants may have migrated to the north as their habitat, the ‘mammoth’ steppe, dwindled," says Johannes Krause, the study's senior author.

Furthermore, the findings show that there had been no genetic exchange between contemporaneous hunter-gatherer populations in western and eastern Europe for more than 6,000 years. Interactions between people from central and eastern Europe can only be detected again from 8,000 years ago. "At that time, hunter-gatherers with distinct ancestries and appearances started to mix with each other. They were different in many aspects, including their skin and eye colour," says He Yu.

During this time agriculture and a sedentary lifestyle spread from Anatolia to Europe. "It is possible that the migration of early farmers into Europe triggered the retreat of hunter-gatherer populations to the northern edge of Europe. At the same time, these two groups started mixing with each other, and continued to do so for around 3,000 years," Krause says.

"The data we gained from this study provides us with astonishingly detailed insights into the developments and encounters of West Eurasian hunter-gatherer groups," Posth summarises. "Further interdisciplinary research will clarify which exact processes were responsible for the genetic replacements of entire Ice Age populations.”

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JOURNAL

Nature

DOI

10.1038/s41586-023-05726-0 

Oldest human genome from southern Spain

 

IMAGE: OVERVIEW OF CUEVA DE MALALMUERZO. view more 

CREDIT: © PEDRO CANTALEJO

An international team of researchers has analysed ancient human DNA from several archaeological sites in Andalucía in southern Spain. The study reports on the oldest genome to date from Cueva del Malalmuerzo in southern Spain, as well as the 7,000 to 5,000-year-old genomes of early farmers from other well-known sites, such as Cueva de Ardales.

The Iberian Peninsula plays an important role in the reconstruction of human population history. As a geographic cul-de-sac in the southwest of Europe, it is on one hand considered a refuge during the last Ice Age with its drastic temperature fluctuations. On the other hand, it may have been one of the starting points for the recolonisation of Europe after the glacial maximum. Indeed, previous studies had reported on the genomic profiles of 13,000 to 8,000-year-old hunter-gatherers from the Iberian Peninsula and provided evidence for the survival and continuation of a much older Palaeolithic lineage that has been replaced in other parts of Europe and is no longer detectable.

After an organism’s death, its DNA is only preserved for a certain period of time and under favourable climatic conditions. Extracting DNA from ancient remains from hot and dry climates is a huge challenge for researchers. In Andalucía, in the south of present-day Spain, climatic conditions are similar to those in North Africa - however, DNA has successfully been recovered of 14,000-year-old human individuals from a cave site in Morocco. The new study fills crucial temporal and spatial gaps. Researchers can now directly investigate the role of the southern Iberian Peninsula as a refuge for Ice Age populations and potential population contacts across the Strait of Gibraltar during the last Ice Age, when sea-levels were much lower than today.

In the right place at the right time

The genetic ancestry of individuals from central and southern Europe who lived before the Last Glacial Maximum (24,000 to 18,000 years before today) differs from the ones who recolonised Europe afterwards. However, the situation in western Europe has not been clear until now due to a lack of genomic data from critical time periods. The 23,000-year-old individual from Cueva del Malalmuerzo near Granada finally adds data from the time when large parts of Europe were covered by massive ice sheets. The study describes a direct genetic link between a 35,000-year-old individual from Belgium and the new genome from Malalmuerzo. “Thanks to the high quality of our data we were able to detect traces of one of the first genetic lineages that settled Eurasia 45,000 years ago. Importantly, we found similarities with a 35,000-year-old individual from Belgium whose ancestry we can now trace further to the 23,000-year-old individual from southern Iberia”, explains first author Vanessa Villalba-Mouco of the Max Planck Institute for Evolutionary Anthropology.

The individual from Cueva del Malalmuerzo not only links to earlier periods of settlement but also to the hunter-gatherers of southern and western Europe who lived long after the last Ice Age. It also confirms the important role of the Iberian Peninsula as a refuge for human populations during the last Ice Age. From there, humans migrated northwards and eastwards once the ice sheets had retreated. “With Malalmuerzo, we managed to find the right place and the right time period to trace a Palaeolithic human group back to one of the proposed Ice Age refugia. It is remarkable to find such a long-lasting genetic legacy on the Iberian Peninsula, especially since this pre-Ice Age ancestry had long since disappeared in other parts of Europe”, adds senior author Wolfgang Haak of the Max Planck Institute for Evolutionary Anthropology.

More puzzle pieces of human history

Interestingly, the authors did not find any genetic link between the southern Iberian Peninsula and North Africa – despite a distance of only 13 kilometres across the Mediterranean Sea, and parallels in the archaeological record. “In Malalmuerzo, we found no evidence of a genetic contribution from North African lineages, and conversely, there is no evidence of a genetic contribution from southern Spain in the genomes of the 14,000-year-old individuals from the Taforalt cave in Morocco”, adds Gerd-Christian Weniger from the University of Cologne. "Why the Strait of Gibraltar was a barrier at the end of the last Ice Age is still one of the unresolved questions of archaeological research in the western Mediterranean region."

The study also includes a number of younger individuals from the Neolithic, a time period when the first farmers arrived in Europe from the Near East. The characteristic genetic ancestry of Anatolian Neolithic groups is indeed detectable in the individuals from Andalucía, suggesting that these early farmers spread over large geographic distances. “Neolithic people from southern Iberia, however, show a higher proportion of hunter-gatherer lineages. Hence, interaction between the last hunters and the first farmers may have been much closer than in other regions”, says co-author Jose Ramos-Muñoz from Universidad de Cádiz.

The Iberian Peninsula’s special role during the Ice Age still resonates thousands of years later. “Surprisingly, the genetic heritage of Paleolithic hunter-gatherers is still detectable in early farmers from southern Iberia, indicating local admixture between two population groups with very different lifestyles”, concludes Vanessa Villalba-Mouco.

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JOURNAL

Nature Ecology & Evolution

DOI

10.1038/s41559-023-01987-0 

Bronze Age well contents reveal the history of animal resources in Mycenae, Greece

 

 

IMAGE: THE PETSAS WELL, WITH BONES HIGHLIGHTED. view more 

CREDIT: MEIER ET AL., 2023, PLOS ONE, CC-BY 4.0 (HTTPS://CREATIVECOMMONS.ORG/LICENSES/BY/4.0/)

A large Bronze Age debris deposit in Mycenae, Greece provides important data for understanding the history of animal resources at the site, according to a study published March 1, 2023 in the open-access journal PLOS ONE by Jacqueline Meier of the University of North Florida and colleagues.

Animals were an important source of subsistence and symbolism at the Late Bronze Age site of Mycenae in Greece, as evidenced by their depictions in art and architecture, but more research is needed on the animals that actually lived there. In this study, researchers performed a detailed analysis of a large deposit of animal remains inside a well within Petsas House, a household in Mycenae that also included a ceramics workshop.

Excavations into the well recovered ceramics, metal, stone, and other materials alongside abundant animal remains, the most common of which were remains from pigs, sheep and goats, cattle, and dogs. Based on the study of the condition of these animal remains, including evidence that many of these animals were used as food, in association with the other finds, especially pottery, the researchers reconstruct that this well was used to collect debris post destruction.

The contents of the well vary across the vertical layers within it, indicating variation in the source formation processes and in the availability of animal resources, both locally sourced and externally provided. These changes might also reflect hardships in the wake of a natural disaster, as the debris within the well appears to have come from cleanup efforts after a destructive earthquake.

The dog remains were more intact than those of the farm animals, and were deposited in the well at a different time. The authors believe this to be tentative evidence that dogs may have been treated differently in death than other animals.

This study demonstrates how detailed analysis of animal remains in well-preserved assemblages can provide insights into social dynamics of ancient settlements. Further investigation into this site will potentially elucidate patterns of food provisioning, trading, and responses to natural disasters at this important archaeological locality.

The authors add: “This study presents new insights about ancient animals recovered from the renowned archaeological site of Mycenae in Greece—a major political center in the Late Bronze Age, famous for references in Homer’s Iliad. Research at Petsas House, a domestic building in Mycenae's settlement used in large part as a ceramics workshop, revealed how the remains of meaty meals and pet dogs were cleaned and disposed of in a house well following a major destructive earthquake. Study of the archaeologically recovered bones, teeth, and shells from the well yielded a more nuanced picture of the diverse and resilient dietary strategies of residents than previously available at Mycenae.”

The freely available article in PLOS ONE: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0280517

JOURNAL

PLoS ONE

DOI

10.1371/journal.pone.0280517 

Waxing and waning of environment influences hominin dispersals across ancient Iran

Peer-Reviewed Publicationp

 

IMAGE: UPLAND TERRAIN IN THE ZAGROS MOUNTAINS DURING SPRING DEMONSTRATING THE ‘GREENING’ OF LANDSCAPES. view more 

CREDIT: GRIFFITH UNIVERSITY

A world-first model of paleoclimate and hydrology in Iran has highlighted favourable routes for Neanderthals and modern human expansions eastwards into Asia. 

Published in PLOS ONE, the findings reveal for the first time that multiple humid periods in ancient Iran led to the expansions of human populations, opening dispersal route across the region, and the possible interactions of species such as Neanderthals and our own Homo sapiens.  

Professor Michael Petraglia, a key researcher in the study, said historic humid periods resulted in massive changes to ecosystems and led the team to identify large lakes in areas that were formerly deserts.  

“Conversely, during glacial periods this increased aridity would have led to the expansion of deserts, led to contractions, and the isolation of hominin populations,” said Professor Petraglia, who is the Director of Griffith’s Australian Research Centre for Human Evolution.  

“This cycle of wetting and drying is shown for the first time in Iran.” 

The research team, led by PhD candidate Mohammad Javad Shoaee from the Max Planck Institute for Geoanthropology in Germany, found that during Marine Isotope Stage (MIS) 5, a warm, humid period beginning roughly 130,000 years ago, lakes and rivers enabled two pathways for human groups.  

One was a northern route through the Alborz and Kopet Dagh Mountains and north of the Dasht-I Kavir desert. The other route, first identified here, ran south along the Zagros Mountains before extending eastwards towards Pakistan and Afghanistan.  

The researchers also found evidence for a potential northern route during MIS 3, beginning about 57,000 years ago, which, given artifacts attributed to multiple tool making groups, could have permitted interactions between modern humans and Neanderthals. 

“These findings highlight the importance of Iran for our species’ dispersals out of Africa and ultimately around the globe,” said Professor Petraglia.  

“As in other regions long considered too arid for early human occupations, such as the Arabian Peninsula, recent palaeoclimatic research is changing how we understand the human story and the role that changing climates have played.” 

“We recognised a new southern route along the Zagros Mountains and extending eastwards towards Pakistan and Afghanistan. We found evidence for a potential northern route during MIS 3, which would have permitted hominin movements and species interactions in Southwest Asia,” Shoaee said. 

To find out how human groups made their way into Iran, the team developed the first spatially comprehensive, high resolution palaeohydrological model for Iran.  

They then compared their model, which showed when and where water was available, to the distribution of previously documented archaeological sites.  

The result was a clear relationship between the availability of water and the evidence of human presence.  

Not only does the current study help to explain the presence of previously documented sites, it also serves as a guide for future archaeological surveys in the region.  

“Our paleohydrological analyses identified 145,354km of rivers and 115 paleolakes calculated from 6380 paleolake deposits. Only a handful of these paleolakes have so far been studied,” Shoaee said.  

By focusing on regions where water once made human occupations possible, Professor Petraglia said “researchers could maximize the potential of finding archaeological sites".   

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JOURNAL

PLoS ONE

DOI

10.1371/journal.pone.0281872