Staying put: the what, when, and how of the first farmers

We’ve all thought about making lifestyle changes at some point. Joining a running group. Going on a diet. Stopping smoking. So did our hunter-gatherer ancestors. They made what would be perhaps one of the greatest lifestyle changes in the history of our species: they started what would become farming. And it caught on, having vast implications for the world we know today.

For most of our time on earth humans have practised what is known as a hunter-gathering lifestyle; a nomadic lifestyle where food, largely meat, is obtained and shared through foraging. Although there are still some groups practising this mode of subsistence, in multiple parts of the world individuals and populations underwent a massive paradigm shift to a new way of life. From the end of the Pleistocene humans began to settle; we began to cultivate the land, to herd animals and drink milk continuously into adulthood. No longer was supply in shortage but instead in surplus.

A comparative timeline of the origins of agriculture and associated technologies. Drawn by Dr. Chris Stevens as part of the ComPAg project.

A comparative timeline of the origins of agriculture and associated technologies. Drawn by Dr. Chris Stevens as part of the ComPAg project.

This way of acquiring food, and by “owning” the land they lived on, spawned social hierarchy, currency and many other socio-political and cultural changes. It was the event that perhaps changed the very nature of our species. This process occurred at least three times around the world: the Middle East, Latin America and China. Farming not only profoundly changed the face of humanity but also changed the terms of humanities relationship with the world. But what drove this change? Researchers are working hard to try and understand why this happened, why it was so successful and how it spread.

Some of the earliest evidence of farming anywhere in the world has been found in the Fertile Crescent (south eastern Turkey, north eastern Iraq, and western Iran); a crescent shaped piece of moist, cultivable land situated between the arid Arabian Desert to the South and the Armenian highlands to the North. Archaeological sites in the region tell stories of rich civilisations with evidence of early crop cultivation and crop storage. For example, the Neolithic site of Chogha Golan (Ilam Province, present-day Iran) is known for a striking record of the cultivation of wild plants and some of the earliest appearances of domesticated crop species such as wheat and barley. Stone tools from the site include mortars, pounders, pestles and grinding slabs for processing grains and other foods. There is also strong evidence for the presence of domesticated livestock in the region including goats, sheep, pigs and cows. Rather importantly, it is also thought to be one of the first places we brewed beer. Based on the archaeological record it appears that from this fertile region farming spread through Turkey, Greece and Cyprus by 6500BCE, and then spread through the Balkans, Central Europe and the Mediterranean eventually reaching Britain around 4000BCE. As a historical process this change is called the Neolithic revolution (the term Neolithic relates to the adoption of agriculture and it’s distinct culture).

Trench at the Neolithic site of Chogha Golan at the foot of the Zagros Mountains, Iran.

Trench at the Neolithic site of Chogha Golan at the foot of the Zagros Mountains, Iran.

By the rate of spread you might think that farming was a sensible idea with immediate rewards. But what remains a puzzle is that at least to begin with, farming doesn’t appear to be that beneficial. Imagine, as a hunter-gatherer, that you decided to try a new strategy and stop moving; to settle in one place and to take up a lifestyle that would become what we now know as farming. As life goes on you begin to face new challenges; living in large groups of people, close to animals, accumulating stinky bio-waste and rubbish. Disease begins spreading between you, between your animals and between your crops. The good wheat you’ve worked hard to grow and store has become ridden with pests. You’re working harder for longer hours with less reward. You think to yourself, tired and shivering with fever, was this really worth it?

So if it wasn’t immediately a good strategy, why did those first hunter-gatherers who started farming keep doing it and why did it catch on? One line of research is exploring the different factors that caused our hunter-gatherer ancestors to make the switch. Using mathematical models it is possible to theoretically simulate various situations and conditions and extrapolate what implications they may have. Using a model-based approach is particularly important in this scenario because we are investigating events that happened a long time ago: you can’t go back in time and investigate using the standard tools an anthropologist might today. Models are also useful where lots of independent factors are interacting in a way that is difficult to understand using intuition, as is the case here.

Recent research exploring the historical dynamics of farming suggests that the development and persistence of farming is most probable in a model where the first hunter-gatherers to start farming were in small groups of a handful or so individuals. They also conclude that ownership of land (property rights) is an important factor and that in some instances it is possible for a farming way of life to persist even if it results in less food than you might get from hunter-gathering – not intuitive at all! So it appears farming may initially have grown from small groups of individuals trying out new methods but where the idea of land ownership was important.

As we’ve said this shift created a corresponding need for new technologies and with it a culture change. Some key definers of Neolithic life include developments in architecture, tools, figurines and jewellery. Pottery was also important, with large jars created to store excess grain becoming more decorated as the Neolithic persisted, allowing many archaeological sites to be defined chronologically based on the kinds of pottery vessels discovered. Burial practice and mythology also changed shown through the appearance of ceremonial monuments including the famous Stonehenge. And of course monuments of this kind only make sense if you live a sedentary life-style. Why bother creating such a spectacle if you have to move on in search of the next meal soon after?

The world famous monument of Stonehenge was erected in the Late Neolithic around 2500BCE.

The world famous monument of Stonehenge was erected in the Late Neolithic around 2500BCE.

Farming didn’t just change us culturally but also genetically and so analysis of DNA is another important tool in exploring this transition. The debate that continued for many years was how farming spread in to Europe from the Near East. Did plucky groups of inventors develop this new way of life and it was swiftly copied throughout Europe by way of word of mouth (the “cultural diffusion” model)? Or did those first farmers migrate to new areas with their novel technology displacing and replacing the existing hunter-gatherer groups they met along the way (“demic diffusion” model)? Although these models should not be regarded as mutually exclusive they do offer a testable hypothesis for geneticists.

One way geneticists have been trying to answer these questions is using DNA extracted from remains of some of the very first European farmers (ancient DNA). By comparing the DNA of early farmer individuals to the DNA of people alive today these competing ideas can be explored. It might seem simple but it turns out that working with very old DNA is fraught with difficulties. When an organism is alive, DNA repair enzymes work hard to maintain the integrity of DNA. After death however these enzymes stop working and the DNA immediately begins to degrade breaking up strands into smaller and smaller pieces and changing the genetic code. This process continues over time and is sped up in warm and wet climates. What’s more, particularly when working with human ancient DNA, there is a high risk of contamination. When the degraded DNA you are trying to work with closely resembles that of you, the researcher in the lab, the excitement of your new discovery is quickly quashed by the realisation you have cross-contaminated your sample! That being said, with improved technology such as next generation sequencing, the field of ancient DNA research is expanding rapidly. One key development was the discovery that the petrous bone of the inner ear contains a startling amount of DNA, hidden, relatively untouched by contaminating bacteria and somewhat immune to the effect of warm temperatures, lying deep within the skull.

Human skeleton from an archaeological excavation in Northern Greece (Paliambela Excavation Project Archive - credit K. Kotsakis and P.Halstead).

Human skeleton from an archaeological excavation in Northern Greece (Paliambela Excavation Project Archive – credit K. Kotsakis and P.Halstead).

DNA extracted from the petrous bone of human remains found in Anatolia and Greece (some of the earliest farming sites) has been used to directly test the hypotheses of demic versus cultural diffusion models. By comparing the DNA of Europeans alive today with DNA from these very early Anatolian and Greek farmers it has been shown that all Neolithic farmers look genetically similar to present day Southern Europeans and that the patterns of shared ancestry extend all the way back to North-West Anatolia. This suggests a wide-spread migration and replacement by farmer individuals moving into Europe and that the change to farming in Europe was mediated by moving people rather than primarily by the spread of ideas.

The story gets more complicated if we consider the genetic status of the first farmer individuals beyond Anatolia. Despite the challenge of the warm climate of the Near East ancient DNA has recently been obtained from human remains from the heart of the Fertile Crescent – those individuals that lived right at the very dawn of farming. Recent work involving three research groups compared DNA from very old human farmer remains found in Fertile Crescent to DNA from other early farmers, late hunter-gatherers and modern individuals. Very strikingly, considering the genetic status of individuals from this region, it was found that there were in fact genetically distinct groups of early farmers occupying this region.

Genetic analyses showed that these early Iranian farmers were not the ancestors of farmers in Europe and instead closely resemble modern day groups from Armenia, Pakistan and India. What is more, ancient DNA samples from early farmers in the Southern Levant (Israel and Jordan) were different again, likely spreading their farming culture southwards in to East Africa. It seems this revolution was brought about by groups of people who were extremely genetically different. These new finds will direct researchers to look for more archaeological sites in order to better characterise how these distinct groups have contributed to present day genetic diversity and what this means for how farming spread to other parts of the globe.

Ancient DNA from human remains in Iran (blue) and Anatolia (red) show very different genetic affinities to modern day populations suggesting multiple origins for farming and evidence of an eastwards expansion (adapted from Broushaki et al. 2016).

Ancient DNA from human remains in Iran (blue) and Anatolia (red) show very different genetic affinities to modern day populations suggesting multiple origins for farming and evidence of an eastwards expansion (adapted from Broushaki et al. 2016).

But we don’t just have to look at humans. Farming involved the domestication of crops and animals and this leaves its own genetic signature. One active line of enquiry is analysing archaeological remains and performing genetic analyses comparing the DNA from present day domestic species to Neolithic plant and animal remains. Barley, for example is largely regarded as a founder crop of Neolithic agriculture. Recent work, which extracted the genome sequences of five 6,000 year-old barley grains (the oldest plant genome reconstructed to date) discovered at Yoram Cave in Israel, found that these first domesticated barley grains are surprisingly genetically similar to modern day domestic barley but strikingly different genetically to the wild forms grown in the Levant today. This suggests that barley was indeed domesticated within the upper Jordan Valley of the Fertile Crescent, which agrees well with known archaeological sites.

The same can also be said of animals. The Zagros region of Iran has largely been regarded as the site of domestication of the goat from the wild Bezoar goat to a domesticate form more like we know today. Ancient DNA analysis, this time of mitochondrial DNA (DNA passed down exclusively through the female line) from goat remains, reveals that this region is the likely progenitor of the domestic goat and that the mitochondrial DNA lineage of goats from this region is the same as that responsible for population expansions into West Iran, the South Caucasus and beyond.

Dry preservation of plant remains from excavations (left) and a well preserved, desiccated barley grain found at Yoram cave (right)

Dry preservation of plant remains from excavations (left) and a well preserved, desiccated barley grain found at Yoram cave (right)

Neolithic goat jaw bone from Göytepe (Image courtesy of Nagoya University).

Neolithic goat jaw bone from Göytepe (Image courtesy of Nagoya University).

So farming was adopted multiple times in the Fertile Crescent by small groups of hunter-gatherers that were remarkably genetically distinct from one another. The spread of farming involved the movement of people who took with them new domesticated forms of plants and animals as well as new technologies, social organisations, culture and ideas. And it was this that profoundly changed the world in which we live today.

Written by Lucy van Dorp (@LucyvanDorp)

Edited by Jan Freedman (@JanFreedman)

Further Reading:

Broushaki, M.G Thomas, V. Link et al. (2016). ‘Early Neolithic Genomes from the Eastern Fertile Crescent’. Science. 353, 6298. pp.499-503. [Abstract only]

Dounias, & A. Froment. (2011). ‘From foraging to farming among present-day forest hunter-gatherers: consequences on diet and health.’ International Forestry Review. 13, 3. pp.294-304. [Abstract only]

Gallego Llorente, S. Connell, E.R. Jones et al. (2016). ‘The genetics of an early Neolithic pastoralist from the Zagros, Iran.’ Scientific Reports. 6. p.31326. [Full article]

Hofmanova, S. Kreutzer, G. Hellenthal et al.,(2016). ‘Early farmers from across Europe directly descended from Neolithic Aegeans.’ PNAS. 113(25). pp.6886-91. [Full article]

Gallagher, S. Shennen, & M.G. Thomas, (2015). ‘Transition to farming more likely for small, conservative groups with property rights, but increased productivity is not essential.’ PNAS. 112(46). pp.14218-23. [Abstract only]

Kadowaki, K. Ohnishi, S. Arai, et al.,(2016). ‘Mitochondrial DNA Analysis of Ancient Domestic Goats in the Southern Caucasus: A Preliminary Result from Neolithic Settlements at Göytepe and Hacı Elamxanlı Tepe.’ International Journal of Osteoarchaeology. pp.1099-1212. [Abstract only]

Lazaridis, D. Nadel, G. Rollefson et al., (2016). ‘Genomic insights into the origin of farming in the ancient Near East.’ Nature. 536. Pp.419-424. [Abstract only]

F.H. Mazdarani, M.T. Akbari, R.M.N. Fard et al., (2014). ‘Molecular dentification of Capra hircus in East Chia Sabz, an Iranian pre-pottery Neolithic site, central Zagros, based on mtDNA.’ The Journal of Animal & Plant Sciences. 24(3). pp.945-950. [Full article]

Mascher, V.J. Schuenemann, U. Davidovich et al., (2016). ‘Genomic analysis of 6,000-year-old cultivated grain illuminates the domestication history of barley.’ Nature Genetics. 48. pp.1089-1093. [Abstract only]

Mathieson, I. Lazaridis, N. Rohland et al., (2015). ‘Genome-wide patterns of selection in 230 ancient Eurasians.’ Nature. 528. pp.499-503. [Abstract only]

Omrak, T. Gunther, C. Valdiosera et al. (2016). ‘Genomic Evidence Establishes Anatolias the Source of the European Neolithic Gene Pool.’ Current Biology. 26(2). pp.270 [Abstract only]

Riehl, M. Zeidi, & N. J. Conard, (2013). ‘Emergence of Agriculture in the Foothills of the Zagros Mountains of Iran.’ Science. 341. pp.65–67. [Abstract only]

Willcox. (2013). ‘The Roots of Cultivation in Southwestern Asia.’ Science. 341. pp.39-40.[Abstract only]

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