Maritime Hunter-Gatherers Adopt Cultivation at the Farming Extreme of Northern Europe 5000 Years Ago

The dynamics of the origins and spread of farming are globally debated in anthropology and archaeology. Lately, numerous aDNA studies have turned the tide in favour of migrations, leaving only a few cases in Neolithic Europe where hunter-gatherers might have adopted agriculture. It is thus widely accepted that agriculture was expanding to its northern extreme in Sweden c. 4000 BC by migrating Funnel Beaker Culture (FBC) farmers. This was followed by intense contacts with local hunter-gatherers, leading to the development of the Pitted Ware Culture (PWC), who nonetheless relied on maritime prey. Here, we present archaeobotanical remains from Sweden and the Åland archipelago (Finland) showing that PWC used free-threshing barley and hulled and free-threshing wheat from c. 3300 BC. We suggest that these hunter-gatherers adopted cultivation from FBC farmers and brought it to islands beyond the 60th parallel north. Based on directly dated grains, land areas suitable for cultivation, and absence of signs of exchange with FBC in Sweden, we argue that PWC cultivated crops in Åland. While we have isotopic and lipid-biomarker proof that their main subsistence was still hunting/fishing/gathering, we argue small-scale cereal use was intended for ritual feasts, when cereal products could have been consumed with pork.


Introduction to supplementary materials
The supplementary results are mainly presented in Supplementary tables 1-11. Radiocarbon dates from the sites studied in this paper are presented in Supplementary table 1. Dated cereals are presented in Supplementary table 2. A compilation of archaeobotanical sites with consistent Early Neolithic and/or Middle Neolithic dates with more than ten plant remains is presented in Supplementary table 3. Detailed results of archaeobotanical analyses from sites published in this article are presented in Supplementary results and Supplementary tables 4-11. Supplementary information on sites is based on published materials and excavation reports from the archives of Ålands Museum in Mariehamn and the Finnish National Board of Antiquities in Helsinki.

Supplementary information on sites Kloddberget
Kloddberget is currently located in a forested and swampy valley with a subsoil of fine-grained till between two steep N-S-oriented hills with exposed bedrock. It is an Early Comb Ware site, and according to C14 dates, it was occupied c. 5200-4300 BC. Patchy and partly overlapping signs of settlement indicate that the site was visited repeatedly. Around c. 4500 BC (55 masl), the site was situated on an approximately 3×4 km island. Kloddberget was situated in a sheltered bay that opened to the south. Contemporaneous sites are situated on other parts of the island. Small amounts of ceramics, lithics of local origin, and whetstones were found at Kloddberget. Archaeobotanical samples derive from Rudolf Gustavsson's excavations in 2007 (ÅM 737) 1 .
Anthracological and archaeobotanical analyses were carried out for three samples by Roger Engelmark 2 . Hearth A contained charcoal from Juniperus sp., Betula, and Alnus and five charred copse-bindweed seeds (Fallopia dumentorum). Hearth B contained charcoal from Juniperus, Alnus, and Pinus.
N/E (WGS84): 60.318685, 20.111137 Typological dating: Early Comb Ware Present research: archaeobotanical study of 12 soil samples with a total volume of 20.5 litres.

Överby
Överby is situated below a hill of barren bedrock. The site is located in a flat area with sandy subsoil that is mostly devoid of stones. Överby is an Early Comb Ware site, and a C14 date indicates that it was occupied during c. 3900-3600 BC. Repeated use of lithics and heating of stones points towards the site being used for longer periods of time. The site was situated on an approximately 1×1 km island, which belonged to a group of small islands, in 4000 BC (50 masl). Överby was situated in a bay facing southwest, sheltered by a nearby cape and islets. Soil samples derive from a hearth dug into the subsoil. Finds from the hearth consist of lithics, a hammerstone, and bones. Archaeobotanical samples derive from Rudolf Gustavsson (Supplementary table 1). When Glamilders was settled in c. 2500 BC (34 masl), it was situated on the westernmost parts of two islands separated by a narrow sound, with a total size of 10×6 km. The site was situated on a southwardpointing cape in a sheltered small bay surrounded by a larger bay. Archaeobotanical material derives from excavations by Rauno Vaara in 2004 11 .
The samples discussed in this article come from trench A in the lower part of the settlement (Fig. 2). Part of the samples were studied by Engelmark et al. 12 The upper part of the settlement has been excavated at various times during the 20 th century. Excavations at Glamilders unearthed intact cultural layers, hearths, house depressions, and postholes. Samples studied from the site originating from the uppermost layer, with recent finds, are not included in this paper. Finds at the site consist of ceramics, lithics, amber, bones, hazelnut shell fragments, and red ochre. Ground stone tools found at the site are numerous and include axes, chisels, a rhomboid-shaped pendant, an awl, whetstones, and a stone with a frog-like relief carving. Flint and amber indicate the presence of imported objects. Partly burned and partly unburned bone material has not been studied in detail, but a preliminary analysis has shown the presence of seals, fish, birds, and possibly also cattle or elk, and pigs.  The Åby site is dominated by Pitted Ware material, and the C14 dates fall between c. 3250 and 2300 cal. BC. The dated material is primarily carbonized seeds and hazelnut shells. The site is situated 26-29 m above sea level, which means that at the time of the settlement, the site was near the seashore, on a low promontory close to the mouth of a narrow bay. More than 50 Pitted Ware sites are currently known about along the coastline east of Åby.
The excavations have yielded many different structures, such as large pits, huts, and graves. In 2014, several large pits with large amounts of pottery, some possible circular hut structures with postholes, and pits with red ochre that we interpret as graves were excavated. However, no human bones were preserved. There seem to be 4-5 areas with a similar set of features -a grave, one or two large pits, and a possible hut. Perhaps these reflect different households.
The archaeological record is dominated by large amounts of pottery (Pitted Ware): 145 kg of pottery was collected in the 2014 excavation, and earlier excavations have resulted in more than 500 kg of pottery. Most of the pottery is of the Fagervik III or Fagervik IV type. Some of the sherds have wear that indicate a secondary use as tools. Also, some animal figurines made of clay were found. The lithics consist of debitage of quartz, quartzite, greenstone, porphyrite, sandstone, and flint and include tools such as greenstone axes and adzes, some flint points, and slate and grinding stones made of sandstone. Some burnt clay and a few fragments of amber have also been found.
The osteological material consists of approximately 1 kg of heavily fragmented and mainly burnt animal bones (c. 10,000 fragments). Fish bones make up 42% of the material and derive mainly from cod with inclusions of pike, eel, salmon, perch, carp, turbot, and herring. Mammal bones make up 36% of the material and derive mainly from beaver and seal, with inclusions of a few ruminants, marten, boar, and medium carnivores. Unidentifiable bones make up 22% of the material.
N/E (WGS84): 58.663475, 16.177410 Typological dating: Late Pitted Ware Present research: Archaeobotanical study of 113 soil samples with a total volume of 208 litres, a study of plant impressions, and radiocarbon dating.

Tråsättra
Tråsättra 15 lies on a sandy, gently sloping terrace that is situated 26-33 metres above sea level. South of the site, the slope has a steeper gradient towards a pasture with clayey soil situated approximately 18 metres above sea level. The sandy terrace is delimited towards the east and west by cliffs that sheltered the location. Towards the north, there are also higher forested areas with bedrock near the surface or even exposed bedrock. The area has never been cultivated since its PWC occupation, and therefore, finds and constructions are well preserved. Several Neolithic sites (c. 4000-2300 BC) are situated near Tråsättra. When the site was in use (c. 2900-2300 BC), the sea level was situated at around 27 masl, and the area was rich in islands. Tråsättra was then located in the outer archipelago on an island measuring approximately 3×4 km. The site lay on a southward-pointing cape in a bay sheltered by nearby islands.
At Tråsättra, the whole site was excavated, and in the central area the cultural layer was sieved in its entirety. The samples discussed in the article come from different parts of the site, but mainly from the area around the houses and the central area between these constructions (Supplementary fig. 7). A rich and varied inventory of finds from the site consists of ceramics, lithics, and bones. Hazelnut shells were collected during the excavations. The ceramics consist of pots with a rim diameter of 3-50 centimetres, and a rich variety of clay figurines has also been found depicting humans, seals, bears, pigs, snakes, elks, and birds. The lithics consist of picks, awls, chisels, scrapers, saws, axes, whetstones, arrowheads, knives, and other types of tools. On the site, there are both burned bones and a small number of unburned bones. Osteological analysis has shown that seals and fish bones predominated, but a large array of bird and terrestrial mammal bones have also been found. Terrestrial species consisted of cattle, dogs, pigs, beaver, wild cats, otter, elk, brown bears, mountain hares, red foxes, polecats, red squirrels, and pine marten. Birds included tufted duck, red-breasted merganser, great crested grebe, northern shoveler, Eurasian wigeon, common scoter, grey heron, and common eider. Fish consisted of perch, pike, cod, carp, salmon, pikeperch, cyprinids, herring, whitefish, and roach. Maritime mammals consisted of harp seals, ringed seals, and porpoises.
N/E (WGS84): 59.472128, 18.350873 Typological dating: Pitted Ware Present research: Archaeobotanical study of soil samples, 46 soil samples in all with a total volume of 138 litres, using a 0.5 mm sieve, and nine samples with a total volume exceeding 225 litres with a 2 mm sieve, a study of plant Impressions, and radiocarbon dating.

Svinvallen
Svinvallen is situated on the same gently sloping sandy hill as Glamilders. The area is currently forested and partly damaged by a sandpit. Svinvallen contains mainly Pitted Ware ceramics. Two radiocarbon dates from Svinvallen (2859-2495 cal BC and 997-551 cal BC) point to a long period of use. During the Pitted Ware phase of Svinvallen (2500 BC, 34 masl), it was situated in the same bay as Glamilders. By around 1000 BC (20 masl), the island had grown much larger and was approximately 12×7 km. The environment had also become much more sheltered. Svinvallen has been excavated at various times, and the soil samples derive from the excavations of 2015. Small-scale excavations revealed a pit, and finds consisted of ceramics, lithics, a whetstone, a clay idol fragment, bones, and hazelnut shell fragments. Both seal and fish bones were identified during a preliminary analysis.

Tengo Nyåker
Tengo Nyåker is situated on the SE slope of a sandy ridge on a southward-facing small sandy spit. Large parts of the slopes are cultivated. Clay areas lie below the site. The site has been typologically dated to the Corded Ware period. Tengo Nyåker was situated 400 m NW of a lakeshore around c. 2500 BC (25 masl), and the closest seashore was a bay near the site of Kauhala, 2 km to the east.
The majority of the material derives from Aarne Äyräpää's excavation in 1926 (NM 8709) 16 and Torsten Edgren's excavation in 1982 (NM 21501) 17 ; the latter excavation was partly unavailable for this study. Structures on the site consist of two hearths, possible postholes, pits, and cultural layers. One of the hearths was possibly used for producing ceramics. Finds from Tengo Nyåker consist of 18 kg of pottery, clay spoon fragments, lithics (axes, adzes and quartz), and a single burned bone.
Ancient lipids from ceramic sherds found at Tengo Nyåker have revealed the remains of dairy fats and ruminant carcass fats 18

Kauhala Oxhaga
Kauhala Oxhaga 19 is situated on the western slope of a sandy NE-running ridge of sandy till. The slope was cultivated during the 20 th century and currently is partly forested and partly a meadow. Clay areas are situated at lower elevations surrounding the site. The site has been typologically dated to the Corded Ware period. Kauhala Oxhaga was situated 300 m NW of the seashore on a sheltered bay at around 2500 BC (25 masl).
Material from Oxhaga has been collected from the fields and nearby forested areas. The finds consists of lithics and Corded Ware ceramics 19

Bäljars 2
Bäljars 2 is a dwelling and cultivation site situated on a sandy ridge in the NW part of Lake Lepinjärvi 20 . At around c. 300 BC, Bäljars was situated in a sheltered bay with access to the Baltic Sea. The area has been cultivated, but it is now covered with buildings. Various pit features, hearths, and ard marks were discovered during the excavations. The finds consisted of ceramics, flint, quartz, and burnt bones. Ceramics consisted mainly of the Morby type, and ceramic sherds with textile impressions and ceramics with striated surface were also found. Geochemical, archaeobotanical, and anthracological analyses were conducted for samples taken during the excavations. Radiocarbon dates from the site range from the Bronze Age to the Medieval Period (Supplementary table 1

Härdalen
Härdalen consists of 54 burnt mounds situated on the slopes of a rocky hill facing mostly southwards. The mound studied here dates back to the Bronze Age and was built over a Stone Age settlement. C14 dates span the years 900-400 cal BC. The site was situated on a small, 0.5×1 km island until 2000 BC (29 masl), when it became part of a larger, 7×2.5 km island. In 1000 BC (20 masl), the former bay east of Härdalen was cut off from the sea and became the still existing Lake Dalsträsk. A zone of fine-grained till surrounds the hill at lower elevations and the sediment in the surrounding valley bottoms is clay. Finds from the mound consist of ceramics, lithics, bones, burned clay, hazelnut shell fragments, and a piece of bronze chain and a human tooth. Archaeobotanical material derives from excavations done by Maija Nunez in 1990 and 1991 21 .
Osteological analysis has revealed the bones of harp seals, ringed seals and porpoises and a human tooth 5 . Bronze-Age levels of the mound contained cattle teeth, a sheep/goat tooth, and a horse tooth. The Pitted Ware layers contained no terrestrial mammals. Bird bones from Härdalen consisted of bones from different Anatids and especially those from the common eider (Somateria mollissima) 22

Ristimäki
Ristimäki 23 is situated in the Aurajoki river valley on a hill approximately 250 m NW of the river. Large areas of clay subsoil are present with patchy rocky areas and areas of sandy till. According to two C14 dates, Ristimäki dates back to 1190-410 cal BC 24 . At around 1000 BC (15 masl), Ristimäki was situated near an estuary and 2 km from the sea. It was thus a sheltered location providing good communication routes. Soil samples and one plant impression on a Kiukainen ware sherd (TYA 863:9) from the site were investigated.

Supplementary results
At Kloddberget, 12 samples from two hearths (A and B) dug into the subsoil were studied (Supplementary Archaeological plant finds from Jettböle II contain ten rose seeds (Rosa sp.), nine rose hips (Rosa sp.), four rose testa fragments (Rosa sp.), and one hazelnut shell fragment (Corylus avellana).
Altogether, 262 charred plant remains were found at Glamilders (Supplementary table 5 (Supplementary table 2). The most common remains were hazelnuts, of which 177 fragments were found in the soil samples. In addition, during the excavations 420 finds containing hazelnut shells were collected, comprising altogether approximately 850 grams of charred hazelnuts (most often a find contained numerous shell fragments). Other plants gathered from the wild consisted of 20 rose remains (Rosa sp.), two crab apple seeds (Malus sylvestris), three root tubers of lesser celandine (Ranunculus ficaria, cf.), and one false oat grass basal internode (Arrhenatherum elatius var. bulbosum). Cultivated plants comprised two naked barley grain (Hordeum vulgare var. nudum, cf.) and one wheat grain (Triticum sp.). Two impressions of barley were discovered in a preliminary study of the ceramics (on sherds ÅM 726:2091, 2271). Aquatic species are represented by three bur-reed seeds (Sparganium erectum, S. natans, Sparganium sp.). Arable weeds or plants growing on the shoreline are represented by one small water-pepper seed (Persicaria minor), two knotgrass seeds (Polygonum aviculare), and two false cleaver seeds (Galium spurium). One Norway spruce needle (Picea abies) from the sample has not been dated (not included in Supplementary table 4), and it might well be a recent intrusion into the sample, which also contains some earthworm cocoons.
A total of 350 charred plant remains were found at the site of Svinvallen (Supplementary table 6, Supplementary fig 6a). Of these remains, 322 were charred hazelnut shells (Corylus avellana). One rose (Rosa sp.) seed represents another gathered plant from the site. A bread/club wheat grain from Svinvallen was dated to the Pitted Ware period and a naked barley grain to the Bronze Age (Supplementary table 2). Cultivated plants are represented by a bread/club wheat grain (Triticum aestivum s.l.) and a naked barley grain (Hordeum vulgare var. nudum). The sample containing the wheat grain also contained false cleaver seeds (Galium spurium) and goosefoot seeds (Chenopodium sp.), which could represent arable weeds accompanying grain.
Ninety-seven charred plant remains were found at Åby (Supplementary tables [10][11]. The majority of these remains (75) were cereals, of which naked barley, hulled barley, and bread/club wheat were identified. In addition, 18 hazelnut shells, Trifolium sp., and Vicia sp. were discovered. Six cereal grains from Åby were dated to the Pitted Ware Period (Supplementary table 2). One impression of emmer/spelt wheat (Triticum dicoccum/spelta) and one impression of bread/club wheat (Triticum aestivum s.l.) were discovered in the ceramics from Åby.
Archaeobotanical material from Tråsättra consisted of 12 charred plant remains; hazelnuts were not quantified (Supplementary table 9). Cultivated plants consisted of barley and bread/club wheat. Wild plants, namely hazel and lesser celandine root tubers, were also found. One possible arable weed, cleaver, was found. Five cereal grains from Åby were dated to the Pitted Ware period (Supplementary table 2