The Mystery Of Why Neolithic British Peoples Switched From Seafood To Milk For 4,000 Years

NeolithicA University of Bristol Past Horizons release notes that recent research has determined that British Neolithic farmers preferred milk over fish as sustenance.

The article observes that farming culture had spread from its origins in the Near East around 12,000 years ago to the northwestern extremes of Europe by the fourth millennium BC or shortly thereafter, and that various models have been proposed to explain the Neolithisation of northern Europe. Resolving these various theories has proved problematic due to poor faunal preservation and a need to have a quantitative methodology to examine disparate locations.

However, the article cites new research by archaeologists and chemists from the University of Bristol and Cardiff University, and published in Proceedings of the Royal Society, that attempts to answer the question of dietary change utilizing multiple evidence strands, and which qualitatively and quantitatively maps subsistence dietary change in the northeast Atlantic archipelagos from the Late Mesolithic into the Neolithic and up to 1400 AD.

The Open Access report, published in Proceedings of The Royal Society B this month, entitled “Immediate replacement of fishing with dairying by the earliest farmers of the northeast Atlantic archipelagos” is co-authored by Lucy J. E. Cramp, Jessica Smyth, Helen Whelton, and Richard P. Evershed of the Organic Geochemistry Unit, School of Chemistry, University of Bristol, UK; Jennifer Jones, Jacqui Mulville, and Niall Sharples of the School of History, Archaeology and Religion, Cardiff University, Cardiff, UK; and Alison Sheridan of National Museums Scotland.

The paper’s coauthors note that their study presents new multi-proxy evidence that qualitatively and quantitatively maps subsistence change in the northeast Atlantic archipelagos from the Late Mesolithic into the Neolithic and beyond. A model involving significant retention of hunter–gatherer–fisher influences was tested against one of the dominant adoptions of farming using a novel suite of lipid biomarkers, including dihydroxy fatty acids, alkanoic acids and stable carbon isotope signatures of individual fatty acids preserved in cooking vessels.

They maintain that these new findings, together with archaeozoological and human skeletal collagen bulk stable carbon isotope proxies, unequivocally confirm rejection of marine resources by early farmers coinciding with the adoption of intensive dairy farming — a pattern of Neolithization that contrasts markedly to what was occurring contemporaneously in the Baltic, suggesting that geographically distinct ecological and cultural influences dictated the evolution of subsistence practices at this critical phase of European prehistory.

The study paper notes that key evidence derived from stable carbon isotope signatures from Mesolithic and Neolithic human bone collagen reveal a marked difference in diet between Mesolithic and Neolithic coastal inhabitants, with assays of bone from the former suggesting a significant marine protein component, while Neolithic individuals display predominantly terrestrial values.

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The co-authors observe that while the faunal assemblages and strong marine isotopic signature in skeletal remains from coastal Late Mesolithic Britain are unambiguous, criticism has been leveled at the interpretation of low or non-existent contributions of marine products to the Neolithic diet. They suggest that this is owing, in part, to lack of sensitivity of the bulk collagen stable isotope approach for low-protein diets combined with possible scrambled routing of dietary carbon, which could render low quantities of marine protein (less than 20%) isotonically invisible [6,7]. Moreover, they note that it has been argued that possible Neolithic shell middens from Ireland and Scotland point to continued marine resource consumption, and the possibility has been raised that the skeletons investigated isotopically were not representative of the Neolithic population of Britain. However, they say these critiques have been robustly rebutted.

In view of this controversy, the researchers sought independent evidence based on the biomolecular and isotopic compositions of lipids preserved in prehistoric pottery from insular and coastal locations from the eastern North Atlantic, including mainland Britain, the Scottish isles and the isles of Man, and Ireland. This is a highly sensitive means of investigating the significance of marine product processing in pottery. Although the characteristic long-chain polyunsaturated fatty acid (PUFA) distributions of fresh marine fats and oils are lost from degraded marine lipids owing to rapid oxidation and polymerization, their recent work has identified more stable marine biomarkers, including alkanoic acids and vicinal dihydroxy acids originating from degradation of poly- and monounsaturated fatty acids, respectively. Although these products may exist only at low concentrations, operating the gas chromatograph/mass spectrometer (GC/MS) in selected ion-monitoring mode greatly enhances sensitivity of the analyses and makes picogram per gram concentrations routinely detectable.

The Bristol team used a compound-specific carbon isotope technique they have developed to identify the actual fats preserved in the cooking pots, showing that dairy products dominated the menu right across Britain and Ireland as soon as cattle and sheep arrived.

The researchers note that determination of the values of n-alkanoic acids provides a robust signature of sources of dietary carbon and metabolism of organisms. Specifically, ruminant species (cattle, sheep and goats) are separable from non-ruminants (e.g. pigs). Milk fats, moreover, are separable from carcass fats, owing to more depleted isotopic signature 13 C values exhibited by octadecanoic acid in the former, resulting from its different biosynthetic origins. Fats and oils of marine origin would exhibit higher 13 C values than terrestrial species, which is confirmed by the scientists’ investigation of approximately 100 aquatic organisms from the North Atlantic. Together, they say these molecular and stable carbon isotope methods constitute a powerful multi-proxy approach for testing theories relating to marine and terrestrial resource processing in pottery vessels.

evershedRThe research team, led by Professor Richard Evershed of the University of Bristol’s School of Chemistry, developed new techniques in an effort to identify fish oils in the pots.

The cross disciplinary model employed in the study involved investigating sites with hunter–gatherer–fisher influences tested against one of the dominant adoptions of farming using a novel suite of lipid biomarkers and stable carbon isotope signatures of individual fatty acids preserved in cooking vessels. The researchers investigated and sampled millions of bone fragments, and the team’s team’s archaeological investigators also examined 1081 ceramic cooking potsherds and 142 associated carbonized deposits, yielding roughly 650 sufficiently well-preserved lipid residues for biomolecular and stable carbon isotopic analysis. A significant proportion of the sherds derived from 48 Neolithic assemblages were chosen to increase sensitivity at this critical time. These sherds included pottery of: (i) Carinated Bowl tradition, before 3700 BC; (ii) the secondary expansion of the Neolithic to insular locations and Middle Neolithic Hebridean, ‘Unstan’ and early Grooved Wares, 3600–2900 BC; and (iii) later Neolithic Grooved and Ronaldsway Ware (2900–2300 BC. Post-firing heat discoloration, the incidence of sooting and the vessel shapes are diagnostic that these types of Neolithic vessels were commonly used for cooking, probably boiling.

A longer chronological dimension was obtained from coastal and insular northern Britain, through the inclusion of 15 sites from the Bronze Age to Norse period. Existing evidence from faunal assemblages and human stable isotope information was also collated. This allowed three strands of proxy evidence for subsistence patterns to be aligned for this region, and hence chronological trends to be studied over 5000 years of prehistory.

mulvilleJThe Bristol researchers’ findings, together with archaeozoological and human skeletal analysis explored by the Cardiff group led by Dr Jacqui Mulville, confirmed that a decline in marine resource usage by early farmers coincided with adoption of intensive dairy farming, with more than 99 percent of the earliest farmer’s cooking pots lacking any marine derived residues.

The article also notes that human bone collagen contains a unique chemical signature for those eating seafood, and while the remains of early fisher folk present this signature, it is lacking in the later farmers, consistent with the absence of marine residues in period pottery artifacts.

The study’s lead author of the study, Dr. Lucy Cramp is cited noting that: “The absence of lipid residues of marine foods in hundreds of cooking pots is really significant. It certainly stacks up with the skeletal isotope evidence to provide a cramplclear picture that seafood was of little importance in the diets of the Neolithic farmers of the region.”

On her UBristol site, Dr. Cramp observes that marine fauna were likely extensively exploited by peoples of the British Isles for tens of thousands of years but finding evidence of consumption of marine resources by prehistoric populations has proved “extremely problematic,” with detection of marine lipids in archaeological pottery samples a challenge due to the rapid oxidation of polyunsaturated fatty acids, which comprise the major, and most characteristic, component of fats of a marine origin. However, Dr. Cramp notes that recent work has shown the persistence of a range of biomarkers, including isoprenoid fatty acids and alkanoic acids extracted from archaeological pottery that had been used to process marine commodities. This process employed involves development of biomarker proxies via further heating experiments of polyunsaturated fatty acids and analysis of modern reference materials, and will be performed alongside large-scale analysis of organic residues extracted from Neolithic and later pottery from inland, coastal and island sites, including the UK, Ireland, France, Spain and Portugal, with the ultimate aim of investigating whether the exploitation of marine resources continued with the advent of farming, albeit at levels which may previously have been undetectable.

alisonsheridanThe ability to milk animals was a revolution in food production, since for the first time, humans did not have to kill animals to obtain food, but had to develop dairy farming and milking skills. In view of this, team member Alison Sheridan from National Museums Scotland concludes that: “The use of cattle for dairy products from the earliest Neolithic confirms the view that farming was introduced by experienced immigrants.”

A presentation by Andrew Curry published last year by the journal Nature titled “Archaeology: The milk revolution” also notes that during the most recent ice age, milk was essentially toxic to adults because after childhood weaning their bodies were unable to produce the lactase enzyme required to break down lactose, the main sugar in milk. Most of the world’s people today are still lactose-intolerant, with only 35 percent of the human population able to digest lactose beyond the age of about seven or eight, and most people who can digest milk can trace their ancestry to Europe, where Curry explains that lactose tolerance seems attributable a single nucleotide in which the DNA base cytosine changed to thymine in a genomic region not far from the lactase gene.

However, Curry observes that as farming gradually replaced hunting and gathering in the Middle East around 11,000 years ago, cattle herders learned how to reduce lactose in dairy products to tolerable levels by fermenting milk to make cheese or yogurt, and after several thousand years of this, a genetic mutation spread through Europe that gives human adults the ability to produce lactase, and therefore drink milk throughout their lives — an adaptation that opened up a rich new source of nutrition that could sustain communities when harvests failed. For more on the lactose/lactase issue, see the full Curry article here.

Viewed together the study findings show that Early British hunters ate a diet rich in venison and wild boar as well as eating quantities of seafood, including seals and shellfish. With the introduction of domestic animals some 6,000 years ago they quickly gave up wild foods and fishing was largely abandoned with people adopting a new diet based around dairying.

Dr. Cramp notes that: “Amazingly, it was another 4,000 years before seafood remains appeared in pots again, during the Iron Age, and it was only with the arrival of the Vikings that fish became a significant part of our diet.”

Why people in the British Isles changed so abruptly from a seafood to farming diet remains a mystery.

Past Horizons
University of Bristol
Cardiff University
Proceedings of the Royal Society B
Nature News

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