Where are the missing boatyards? Steaming pits as boat building sites in the Nordic Bronze Age

: The boat stands out as a prominent symbol of the Nordic Bronze Age, depicted at thousands of rock art sites and on several metal objects throughout Scandinavia. Paradoxically, direct evidence of these boats is scarce, and the locations where boats were constructed remain largely elusive. In this paper, we put forth the proposition that many ostensibly mislabelled cooking pits along the coast might actually be remnants of steaming pits employed in boat building. By drawing on analogous parallels from eth-nography and examining three Bronze Age cases from the western coast of Sweden and Eastern Norway, we hypothesize that sizable pits near the sea, characterized by fire-cracked stones and charcoal, are indicative of prehistoric boat building sites. Additionally, these results align with a broader objective of our paper, aiming to challenge the prevailing terrestrial narrative in archaeology, which has impeded the interpretive potential for comprehending maritime societies throughout prehistory.


Introduction
The importance of the sea and waterways during the Nordic Bronze Age have been emphasized as a focal point for progresses and changes in political and social organization, the forming of alliances and networks, and for the control of goods as well as of people1.A martime mode of production has lately been suggested as a way to regulate Scandinavian Bronze Age societies.2Thus, the significance of boats in these societies cannot be overstated, and both direct and indirect evidence of boats has been extensively studied3.However, sites or features that can be related to prehistoric boatbuilding remain extraordinarily rare to the point of almost being absent in the archaeological record4.But is this really the case?Could it be that there are finds and features that need to be re-examined and reinterpreted?We argue that the process of boat building has been overlooked by many archaeologists and that there exist more finds, materials and features that can be related to this phenomenon.
In this paper we will focus on one particular feature that traditionally been coined as cooking pits.We propose that some of these features are more likely to be associated steaming or heating processes in connection to boatbuilding in prehistory, for example for expanding logs or bending wooden planks.We support this hypothesis through the analysis of four case studies.The first regards ethnographical data that accounts for the use of steaming or heating pits for boat budling building in different regions around the world.The following case studies are based on archaeological recordings of such features from the west coast of Sweden, i. e. the counties of Bohuslän and Halland, as well as the costal county of Østfold in southeastern Norway.Before delving deeper into this topic, we'll provide a brief review of the direct and indirect evidence supporting ancient boats and boat building in northern Europe.

Background
As coasts and seas are high energy environments, archaeological evidence of ancient boats and boat building is rare and often hard to identify.In northern and north-western Europe, direct archaeological evidence of prehistoric boats is primarily based on a rich collection of logboat material, but also a single bark boat from riverine or estuarine contexts, with logboats featuring the longest continuity from the c. 9th millennium BCE onwards, whereas the bark boat is dated to c. 800 cal.BCE5.There are also the remains of some 14 plankbuilt vessels from various coastal British and Scandinavian locations, in time ranging from c. 2000-100 cal.BCE6 (Fig. 1).In addition to the above direct evidence of actual boat finds boats, there is also the indirect evidence of a rich hide boat tradition from mainly British waters from at least the 6th century BCE but possibly extending back to the Mesolithic7.
Apart from only one or two sites found so far within the entire northern and north-western Europe8, sites or features that can be related to prehistoric boat building remain extraordinarily rare.Nevertheless, many archaeological boat finds bear clear signs of having been worked with woodworking tools such as axes, adzes and drills, of types that have clear parallels within the local or regional archaeological record and could perhaps be used to identify boat related practices9.In addition, comparisons with ethnographic data on various boat building tools, methods and practices might offer ways to better understand particular processes of prehistoric boat building in Northern Europe10.
However, indirect evidence does exist of boat building and maintenance activity in Scandinavia during the Bronze Age.Tars, resins, and animal fats were critical components of boat building practices as they were needed to waterproof seams between planks11.These materials were also used in combination with moss to plug holes and conduct maintenance on ancient boats12.In Scandinavia, over 70 tar, resin, and pitch loaves have been found in contexts which could date to the Bronze Age13.Bronze Age loaves are circular and have a small hole in the center, indicating they were carried on a rod or string (Fig. 2).Multiple loaves were likely transported together, and their distribution is closely tied to the coast, indicating they were transported by boats14.Evidence of transom built logboats and repair "kits" that include bark, 3-ply string and a lump of resinous moss has e. g. been found in Danish contexts dating already from the 6 th millennium BCE15.A lump of a pure oil-based substance has also been found on the c. 350 BCE Hjortspring boat, found in a bog on the Island of Als, Denmark, in 1922, where the same substance was found to have been mixed with some sort of animal fat in the caulking material covering the seams in-between the planks16.
Other indirect evidence that indicates the importance of boats are found within the local rock art tradition in Scandinavia, featuring over 20 000 boat images, as well as the remains of large stone monuments, so called ship-settings, laid in the shape of boats and with those dated to the Bronze Age likely to represent the shape and size of authentic vessels17.(Fig. 3-4) The aforementioned information renders the pursuit of novel approaches to pinpoint locations associated with the building and maintenance of prehistoric vessels.Nonetheless, the question remains as to where exactly boats were built and whether these locations can be identified in the archaeological record.
In the subsequent discussion, we contend that some characteristics that have conventionally been categorized as cooking pits might be reevaluated as features employed for the purpose of heating or steaming specific timber elements within the field of boat building.We base this assumption on the location of these features in landscape, their content, form, and chronology, as well as via the use of similar features based on ethnographical evidence.We argue that these features could be defined as steaming or heating pits for boatbuilding and that the identification of these features can add a new line of evidence to our understanding of maritime traditions in prehistoric northern Europe.

Steaming Pits as Boat Building Features
Evidence of the use of fire and steam as part of the boatbuilding practice in western and northern Europe can be traced back to the 1st century CE18.Evidence of fire found in connection to many prehistoric logboats is usually associated with 18 Crumlin-Pedersen/Jensen 2018.small fireplaces, perhaps used for preparing food, keeping warmth or as part of fishing strategies.However, the findings of charcoal dated to c. 5400 cal.BCE in connection to a logboat of lime tree (linden) from Hardinxveld De Bruin in the Netherlands could be evidence of fire used as part of the hollowing out process when building this particular boat19.Apart  from this boat, Arnold20 has argued that an almost 9-meter long logboat of oak, dated to c. 4700 cal.BCE and found on a palaeo-channel of the river Seine, was expanded using heated water and steam.Thus, some fragmentary evidence does exist in the archaeological record of ancient Europe for the potential use of steam to expand and modify boats21.
Traditionally, the process of steaming was carried out using an open fire.The boatbuilder would briefly submerge the wood in water or utilize recently cut or split fresh timber.The wood was then heated over an open flame until it reached a pliable state which allowed it to be twisted and curved to fit neatly in the boat.This procedure involved subjecting the wood to fire, resulting in a lightly charred surface, at the same time enhancing its resistance to decay.This is a technique which remains viable today as an alterntive to wood impregnation22.
Evidence of steaming sites associated with boat building should be identifiable in the archaeological record.Of  Thyselius et al. 1923Thyselius et al. -1937, 758. , 758.special interest are sites with pits with stones affected by sever heat and a large amount of soot, charcoal or burnt wood at ancient seaside locations, dated from Neolithic times onwards in Scandinavia23 (Fig. 5).Ethnographic studies document similar features at similar seaside locations used to steam, bend and expand timber and planks for both dugout canoes and plank-built boats, we will discuss this more below24.Various interpretation models have been applied to these pits over time from drying of foodstuffs such as grain and meat, some function in connection with crafts, such steaming of wood or ritual sauna baths or as territorial markers25.
The hypothesis that shore-connected cooking pits dated to the Bronze Age in Tanum in western Sweden may have been utilized for the purpose of building or repairing boats was first proposed by Petersson26, who supported this argu-   ment by noting that the wood discovered in these features was suitable for the process of steaming or heating wood for construction.This hypothesis received additional support from a fieldwork and literature survey conducted in British Columbia27.In the following, we present a hypothesis that suggests a connection between these features and the construction and repair of boats.We support this hypothesis through the analysis of ethnographic examples and three case studies from the Nordic Bronze Age.

Ethnographic Examples
The possibility that steaming pits in northern Europe were used to build boats can be supported through comparison to abundant ethnographic and ethnohistoric examples of boatbuilding from around the world.Across North America and the Pacific Ocean, many boat building cultures used fire to hollow out logs during the construction of both dugouts and larger plank canoes28.Steam was also used to soften logs and allow for the shaping and widening of canoes29.
27 Ling et al. 2021. 28 Best 1925;Goldenweiser 1940;Kroeber 1976;Olson 1927;Wood 2018. 29 Arima 1983;Ling et al. 2020;Moss 2008.Canoe construction also often required large amounts of tar and pitch for caulking and waterproofing, which would have needed to be melted, mixed, and kept soft through the use of fire30.All of these activities could have involved the use of fire pits similar to those found in coastal Scandinavia and showcase the importance of fires and firepits for traditional boatbuilding practices (Fig. 6).
One of the most common uses of fire in the construction of traditional canoes involved burning out the centre of a log prior to shaping the form of a dugout canoe using a stone adze.In New Zealand, for example, the British explorer Captain James Cook described canoes he observed in Mercury Bay as "trunks of a single tree hollowed out by fire"31.In Polynesia, canoes were often hollowed out by building a fire on top of a split log.Māori writer W. B. Otorohanga described the burning out of a log by saying "a fire is built along its centre, lengthwise, and slaves stand ready with water-gourds and watch where it over-croaches to quench it.The fire dies: the charred wood is chipped off, and so the body is rough-hollowed"32.Fire was also used to hollow out logs for dugout canoes in indigenous California 30 Fauvelle 2011; Hudson et al. 1978. 31 Best 1925, 128. 32 Best 1925, 59. and on the Pacific Northwest coast33.During ethnographic fieldwork carried out on the Haida Gawii Island in British Columbia, Haida boatbuilder Christian White conveyed to Ling and colleagues that traditional methods involved using fire to heat stones which were placed in water to create steam.34The steam from the heated water was then used to bend wood used in the construction of boats.White specified that firepits were placed near boat construction sites for this purpose.Similar hollowing out practices were also used by indigenous people in the Mississippi region of North America, where fires were also built under logs to split them, and red-hot stones were sometimes places onto split logs to assist with hollowing them out35.These ethnographic practices strongly parallel the pattern seen for Bronze Age Scandinavia, where fire pits are placed near beach landings that would have made perfect sites for boat building.
In addition to hollowing out canoes, fire was also used to create steam to assist with bending and expanding canoe sides36.This process involves filling a hollowed-out canoe with water and placing hot stones inside the canoe to produce large amounts of steam.Pressure is then applied on the sides of the canoe to slowly expand it until it reaches the desired width and form.Steam widening of canoes was a common practice on the Pacific Northwest coast of North America and was the means through which the large war and trading canoes of Haida, Tlingit, Kwakiutl and Bella-Coola were constructed37.Modern canoes are still built by indigenous people on in the Pacific Northwest using the same methods38.In order to produce the numerous hot rocks needed for this process, large fire-pits similar to those found in Bronze Age Scandinavia would have been needed.After canoe construction, these stones are often left fire-affected and cracked, much like similar stones found in archaeological contexts.
Fire would have been required to melt and apply the pitches and tars necessary to caulk and waterproof plankbuilt boats.Tar and pitch were often stored in the form of dried cakes, which would have needed to be melted before application39.As a great deal of tar would have been needed to waterproof a whole boat, this process would have required large and sustained fire pits40.In some cases, hot  Hudson et al. 1978.rocks were used to melt tar.The Chumash of Southern California, for example, heated stones in fire pits which were then added to pots of pitch and bitumen to keep the mixture warm and malleable while adding it to the planks of sewn canoes41.This practice produced firepits similar to those needed for steaming canoes.
We believe that several archaeological sites in Scandinavia may correspond to ethnographic descriptions of steaming and fireplaces used for boat building.The presence of steaming pits in proximity to coastal sites fits well with the ethnographic analogies described above and is documented from numerous regions of Scandinavia.In the following we present evidence from three areas in western Sweden and southern Norway (cp Fig 5).

Archaeological Case Studies
Of special importance for this study is the research on shore connected cooking pits conducted by scholars at Bohusläns museum42.These articles and reports give a substantial account and detailed description of cocking pits dated to Bronze Age and Early Iron Age in the county of Bohuslän (Fig. 7).For instance, Lönn and Claesson43 acknowledge that Sophus Müller once coined the concept "cooking pit" and argued for a functional feature connected to settlement.Later anthropological analogies have also inspired this viewpoint and these features have therefore related to cooking, as the name implies.However, the absence of charred food remains, ceramics, and other artefacts in excavated cooking pits makes it difficult to attribute them to practical uses like food preparation or crafting.Lönn and Claesson further suggest that cooking pits should have been significantly more common in prehistory if they had been used for cooking on a regular basis, which in turn challenges the notion that all these pits were used for cooking44.The question that has puzzled these researchers are why they are so common in the Bronze Age and why they are located on the seashore.
The criteria utilised by the archaeologists mentioned above for selecting places with steaming pits are of significance for our selection of case studies: -Located on the seashore next to shallow bays.
-Leeward locations by the foot of a hill or a ridge.
-Accessible location for landing and pulling up boats.
41 Hudson et al. 1978 -Mostly circular about 0.4-3 (some even larger) in diameter, 0.3-0.9meters deep, but also larger, dominated by fire cracked stones, charcoal, and soot.-Including favourable wood for the process of steaming or heating.-The pit(s) would not be used part of a secondary domestic context, but rather serve as primarily features for heating or steaming at the sites.
The subsequent case studies all share a combination of these features.The discussed sites were coastal locations that provided ideal conditions for boat construction and transportation, with convenient access to timber.Evidence of deforestation throughout the Bronze Age indicates the heavy use of wood at these sites, which may have been partially caused by boat building.The strong evidence of bronze casting in these different coastal areas indicate their significance as hubs for the production and distribution of metals.

Bohuslän
Bohuslän is a historical county located on the west coast in southern Sweden and borders the Norwegian county of Østfold to the north and the Swedish county of Halland in the south.Much of the landscape is dominated by plateaus and ridges of granite bed rock that are intersected by fissure valley terrain, formed through the process of erosion of the bedrock's joints.The abundance of plateaus also forms the archipelago that runs along the entire coast, providing a relatively sheltered area for boats to operate45.The coast of Bohuslän faces the strait of Skagerrak which connects the Baltic to the North Sea.The coastal region of Bohuslän, with its maritime location and its maritime history, ethnography, and economy, has always been associated with the sea.From here the entrance to both the Oslo fjord to the north and the access to the Danish Isles and the passage to Thy can be controlled.Most of the prehistoric remains are also oriented towards the sea.The earliest settlement sites from the Mesolithic are strongly associated with the sea-shore when marine utilization dominated the economy46.
Neolithic activity also seems to have been oriented towards the sea.Settlements and megalithic graves are often located on or in the vicinity of the contemporary shore and livelihood seems to have come from both maritime and terrestrial sources47.During the Neolithic between 3300-3000 BCE collective burial sites, so-called megalithic tombs, have been constructed concentrating along a narrow strip along Bohuslän's coast.The first phase of deforestation and expansion of heathland began around 2000 BCE in Northern   Bohsulän and lasted until about 500 BCE48.It is notable that this change in the landscape correlates with the archaeological record of bronze items, flint daggers and sickles from the Late Neolithic and Early Bronze Age.This could indicate that timber was needed for boat building, not just for household activities and metallurgy.The overall archaeological record demonstrates intense maritime interactions during the BA.It is therefore logical to assume that boats were produced on a local basis.
Several aspects of the archaeological record of Bohuslän point to the possibility of substantial boat building activities in prehistory.A total number of 1040 simple shaft-hole axes have been registered in the county of Bo-huslän49.This type of axe has been argued to have been used for timber production i. e. boat building50.Moreover, Bohuslän has Europe's largest concentration of prehistoric rock art; about 1500 sites have been recorded, no other area with South Scandinavian Bronze Age rock art presents such a rich figurative repertoire and complex compositions of images as Bohuslän (Fig. 8).Multiple compelling factors support the notion that the rock art regions may have functioned as a hub for the construction of boats51.Firstly, the rock art imagery features scenes and details that can be directly compared to the process of building the c. 350 BCE Hjortspring boat,52.Secondly, the landscape with its fissure valleys mainly running perpendicular to the sea means communication by boat would have been essential, something that the rock art boat imagery support.Coupled with evidence of deforestation within rock art areas during the Bronze Age, this could indicate that timber was needed for boatbuilding, not just for household activities and metallurgy.Boats need even more wood, because of constant maintenance for the planks not to rot or warp53.In addition, vast quantities of ropes would have been needed, not only for fastening planks, but for the general handling of boats -examples of which is also depicted in the rock art, with use of anchors.Finally, the spatial distribution of the rock art here appears to document a ritual chain of boat building from higher ground, where trees were cut for the craft, to adjacent to settlements where crafts were roughed out, and, finally, at launching sites for departure and return.

Steaming Pits
Around 40 sites of steaming pits dated to the Neolithic or Bronze Age have been identified in Bohuslän that can be related to this case study54.We will focus on a specific case from Tanum but also account for some other sites in the region.
On the western part of the Island of Orust, at the site Morlanda 354, a total of seventeen steaming pits were in-vestigated55.The pits were about 1-2.5 meters in diameter and 0.25-0.9meters deep, they included no evidence food remains just some scattered flints and ceramics.There is no information on which type of wood was used for carbon dates, although, they fulfil most of the other said criteria's for our case.Eight of these features were carbon dated to the Early and Late Bronze Age and were thus located just at the seashore during this phase56.We hold that the steaming pits on the former sea shores indicates that it could have served as place or building or repairing boats for during the entire Bronze Age.The site in question was then located on a highly communicative passage, in middle of a strait that cut through the island on the western part with Bronze Age cairns leading through from the southern part to the north (Fig. 8).
The site of outermost interest for this study are located in Tanum, In the Bronze Age it was situated on a beach strip adjacent to the entrance to an old sea inlet that linked Tanumsslätten, the largest concentration of Bronze Age rock art in Europe57 (Fig. 8-9).The first phase of deforestation and expansion of heathland began around 1800 BCE in Tanum58.It is notable that this change in the landscape correlates with the archaeological record of imported bronze items, flint daggers and sickles from Jutland to Tanum, dated from the Late Neolithic and to the Bronze Age.This interaction would have demanded locally produced boats and the deforestation that took place in Early Bronze Age could indicate that timber was needed for boatbuilding, not just for household activities and metallurgy.One possible location for this production could be the site 1835 at Tanum.A total of 32 cooking pits were discovered at this location and the 14 C date suggests that these were predominantly used in the Late Bronze Age (Fig. 10)59.The dimensions of the pits were about 1-3 metres in diameter and 0.2-0.6 metres in depth, including soot, charcoal, and fire cracked stones.The  art site, located 5 km south of here, which includes a big pole or mast with warriors attached to it or hanging from it (Fig. 13).In the Bronze Age the site was made at the water's edge it has therefore been suggested that the image represents a maritime initiation rite, conducted either before, during or after a major event at sea61.Such a scenario could 61 Ling 2014, 87; 136.Additionally, several shallow likely postholes were discovered in the part of the of the site62.These postholes were arranged in a semicircular pattern, with a central post hole and hearth base located within the semicircle (Fig. 12).This feature was identified as the remnants of a man-made construction, potentially serving as a windbreak according to 62 Petersson 2009.
Petersson63.However, it is also tempting to suggest that this construction likewise could have been some sort of a simple "naust" i. e. a boat house that could house a boat of about 8-12 meters in length.Looking at the proportions of boats and crew depicted on the rock art compared to real boats, suggest that the most common vessel was about 8-12 meter in length and held a crew of about 6-1064, which we argue  favours the idea of that this construction could be meant for a boat.
Thus, the location of the site in the landscape, at the seashore and at leeward location at the foot of a large hill and at the inlet of the big bay favours also a place for boatbuilding ( 14).The timber for boat building could partly have been sourced from the uppermost part of the extensive ridge that offered shelter to the area, now densely forested with towering pine (Pinus), trees.In addition, timber might have been obtained from the several streams originating from the densely forested areas in the east, converging at this shallow bay during the Bronze Age.Regarding the contents of the pits at the site, Petersson65 offers an intriguing comment in relation to the steaming and heating of wood for boats.The analysis of wood shows that most of the pits contained charcoal from pine66.This type of wood is suitable for making boats, as firewood for steaming and heating, but pine is also a resin-rich tree ideal to produce tar.All these features favour the idea that these pits were the results of building or repairing boats.

Halland
The coastal county of Halland is situated in Southwestern Sweden.The province comprises a landscape of valleys, ridges and of an extensive web of rivers and streams.The province is characterized by four major rivers, stretching from the long coastal zone in the west, through a coastal plain and an undulating intermediate area, ending in the South Swedish highlands and the far-reaching woodlands in the east.In contrast to the northern part of Halland, which forms a rift valley landscape with rugged cliffs and sea meadows, the gently undulating southern area encompasses extensive sandy beaches and plains.These geological alterations may have offered a diversity of resource capacities, creating comparative advantages for different groups throughout the Bronze Age.
The geographical characteristics of the landscape have provided opportunities for communication over sandy ridges and along the coast and river systems, providing connectivity between groups for exchange of goods, resources and various necessities.The extensive deciduous woodlands have provided possibilities for resource utilization with good access to timber and likelihoods for production of resin and tar.An expanding deforestation during the Bronze Age caused by an increase in arable land and emergent heaths, as evidenced in pollen analyses67, may also have occurred due to an excessive need for timber.Over 500 shafthole axes of stone have been recorded in the province68, a tool prominent for wood working, felling trees and cleaving wood69, suggesting an extensive resource utilization of the woodlands.This distinct need may be caused by the building of larger three-aisled timber consuming longhouses at the beginning of the Bronze Age and for casting of bronze70 but also the building of boats, in order for groups to be able to partake in, and access goods through, long distance trade.

Steaming Pits
Based on data collected from contract archaeological exca-vations71, more than 60 excavated sites contain features known as cooking pits, 14 C-dated to the Nordic Bronze Age.Due to high standard deviations the calibrated 14 C-dated features in the study includes the second part of the Late Neolithic, extending the period ca 2000-500 cal BCE (BP 3450-2430)72.
Cooking-pits are commonly occurring on Bronze Age settlements in Halland and are often not 14 C-dated, hence the amount of known cooking pits is even higher.They are often considered a typical Bronze Age feature.However, 14 C-dated cooking pits show a much broader chronological time frame from the Mesolithic to the Viking Age, though the absolute major usage of cooking pits sets to the middle Bronze Age73.
Excavated cooking-pits often lack archaeobotanical remains, ceramics or other finds wherefore they are problematic to relate to functional activities such as food preparation or crafting.Although evidence for specialized activities related to cooking pits, such as for instance preparation and roasting seeds do occur74, however, the majority of features lack proofs for such remains.Among the excavated cooking-pit sites, nine sites may hypothetically be related to boatbuilding, i. e. features containing no evidence of food preparation, situated in close proximity to waterways or the coast, and evidence of tools for cleaving and cutting wood in the vicinity or on the site.Seven of these sites are situ-  The riverine site of Arlösa75 was situated on a slightly sloping west facing bank of the river Nissan, in the southern part of Halland.The area is known for its hollow ways, suggesting an important crossroads and passage over the river in prehistoric and historic times.The site comprised two nearby sites with one steaming pit and two hearths (L2022:7208), and five steaming pits and two pits (L2022:7207). 14C-dates of one steaming pit on each site suggests a contemporary use of the sites during the Middle Bronze Age (1056-898, 2σ Cal. BCE;1013-836, 2σ Cal.BCE).The size of the pits on these sites were between 0.6 and 1.5 meters in diameter and a depth between 0.3 and 0.8 meters.The steaming pits were filled with fire-cracked stones and charcoal, and in one case with two distinct layers of charcoal suggesting reuse (Fig. 15).Except for one steaming pit with rusticated ceramics with a crust, no other finds or archaeobotanical remains are related to the excavation at the sites.However, a simple shaft-hole axe of stone, a stone axe, an arrowhead, scrapes, a sickle and several other flint flakes and bladelets have been found at a site in close vicin-75 Carlsson 2023a; 2023b.ity to the steaming pit sites (L1997:2551), suggesting crafting in the area that may be related to the steaming pit sites.
Woodworking in the area is suggested by the axes and the analyzed charcoal from the steaming pits, is partly comparable to wood-species used to construct the Roman Iron Age boat from Slusegård, dated to the 1st and 2nd century CE and the 3rd-6th century CE Germanic Iron Age boat from Björke76.The charcoal from one of the steaming pits comprised hazel (Corylus) and in one of, mainly, fir (Pinus), but also oak (Quercus), hazel (Corylus), maple (Acer) and rowan (Sorbus)77.This may suggest the usage of spare wood from the actual boat/s for the fires in the steaming pits.
The second site was situated on flat ground at Träslövsläge78, approximately 0.6 kilometers from the Bronze Age shoreline, in the middle part of Halland.Within the excavated site, seven round features known as cooking pits were uncovered, containing fire-cracked stones, charcoal, and soot.Distinct layers of charcoal also suggest reuse of the features.Six of the features were between 2 and 2.5 meters in diameter and had a depth of 0.6-1.0meters.One feature was slightly smaller, extending 0.84 meters in diam-  eter with a depth of 0.3 meters.No finds were found within the features but several flint flakes, a bladelet and two flake end-scrapers were found on site, close to the cooking pits.No archaeobotanical remains were found in the fillings of the pits and although the high amount of charcoal, no wood species analyses were being made.However, usewear analyses on the flint material have provided results suggesting woodworking and cutting fish.The scrapers and two of the flakes were used for scraping and cutting wood, and the bladelet and four of the flakes were used for cutting fish.The processing of fish on the site is also correlating with results from a conducted soil phosphate analysis.In between and under some of the features, phosphates indicate a higher degree of organic residue, most probably originating from meat and/or fish79.
As hypothesized, heating and steaming wood for extending logs or bending planks in boat building demands 79 Johansson 2000.fire, stones, and water80.As evidenced by pollen analyses, deforestation during the period suggests a timber consuming society where the need for wood, including wood for the purpose of boatbuilding may have had an impact on the environment.Although in a farther distance from the shoreline, the site at Träslövsläge holds interesting details that may be discussed further in relation to boat building.As in the case of the steaming pit sites in Arlösa, shaft-hole axes in the vicinity of the site of Träslövsläge, may further suggest woodworking in the area.No other remains of settlement related features or finds at the site, as for instance ceramics or house structures; the reuse of the features; and the evidence of woodworking, based on the use wear analyses, and the close spatial relation to the shoreline, may in fact adhere to the suggestion of the features as remains of hypothetical steaming pits used in boat building.

Østfold
The region of Østfold is situated on the eastern side of the Oslo-fjord bordering Sweden towards the east and south.The landscape is divided in two by the largest moraine ridge in Scandinavia that creates a natural separation between a coastal zone with low-lying plains and a more rugged inland zone recognized by rivers and woodland.In terms of climate, the region is mostly placed within the borenemoral vegetation zone81.This zone is today distinguished by warm summers, frequent rainfalls, and mild winters, and coniferous woodland82.
Connecting the region is the river Glomma, which stretches 654 km inland.The river flows through densely forested regions and in historical times the river acted as an important route for log driving with several sawmills 81 Moen 1999. 82 Moen 1999.operating at its mouth83.In prehistory the river would have been an important gateway into the interior landscape and judging from the spatial distribution of archaeological finds the river was actively used form the Mesolithic and onward.Although somewhat speculative, judging from some of the axe finds dated to the Late Neolithic-Bronze Age that has been discovered along the river, it is not unthinkable that the river functioned as a route for log driving as early as the Bronze Age.Apart from having easy access into the interior landscape, the region also benefitted from its coastal connectivity (Fig. 16-17).In particular, as a bottleneck for maritime trade and control combined with costal stretches of land with well-drained soils suitable for farming84.
The region's central position seems to have been capitalized on at an early stage, and already during the Late Neolithic the archaeological record point to an influx of 83 Vestheim 1998.84 Melheim et al. 2016;Sand-Eriksen 2023.new technological innovations such as cereal cultivation, animal husbandry and sedentism in the form of two-aisled and later three-aisled longhouses85.This period also marks a noticeable increase in Plantago lanceolata in the pollen diagrams86, which may be indicative of deforestation and increased use of timber resources -potentially towards an investment in ship building.This is supported by the archaeological record boasting several metal deposits, monumental coastal cairns, shore-bound metalworking site, longhouse settlements and over a thousand registered rock art sites87.The number of rock art boat images is particular noteworthy.The boat motifs symbolize a region deeply connected to a maritime way of living.The motifs share stylistic connections to other parts of Scandinavia, particularly Bohuslän, but also more far-reach-85 Sand-Eriksen/Mjaerum 2023.86 E.g.Vogt 2012.87 E.g.Melheim et al. 2016;Sand-Eriksen 2023;Tangen et al. 2022;Vogt 2012.ing coastal regions, such as Rogaland and Trøndelag88.All these regions could potentially represent coastal hubs for boatbuilding activity.

Steaming Pits
In contrast to Sweden, most pits with fire-cracked stones in Norway are dated to the Early Iron Age89.However, they are not uncommon in the Bronze Age, and pits have been dated as far back as the Mesolithic90.Pits with fire-cracked stones is a relatively common archaeological feature at archaeological excavations, but explanations tend to lean towards feasting or other ritual activities91, despite the fact that organic remains are rarely recovered.Excluding pits with mentions of burnt bone and other foodstuff there are 154 so-called cooking pits in the national registry dated to the Bronze Age in the region of Viken, which Østfold is part of.Of these, 18 are situated close the sea, of which 9 are located by a coastal leeward.If we include pits close to waterways connected to the sea, the number rises to 49.
Looking into some of the more noteworthy cases, the area around Borge stands out.The site is located relatively close to the coast but also benefit from being near a larger lake.During a development led excavation several pits where registered and excavated, however, the site also revealed two Late Bronze Age houses and a metal celt, most likely used for woodworking activities92.Over 20 fireplaces and three pits were registered at the site.Some of the registered fireplaces contained fire-cracked stones and radiocarbon dated to the Early Bronze Age, which would suggest that the site was used over a longer period of time.The pits did not contain any foodstuff or bones but did hold large amounts of fire-cracked stones and charcoal identified as broad-leaved deciduous wood such as oak93, which would be excellent for making both log and plank-built boats.The sizes of the pits were relatively large, with shapes ranging from circular to more oval.Two of the pits were radiocarbon dated to the transition Early to Late Bronze Age (2925+ 35 BP, TUa-5230, 2855 + 35 BP, TUa-5234).
Another interesting case is Hunn.The site lies at the end of a small fjord by a protective harbour and is perhaps best known for its Iron Age stone circles.Still, another equally important discovery are the excavations of a metalworking site from the Bronze Age94.Evidence of metalworking is based on the discovery of metalworking tools, such as crucibles and tuyeres made of clay.The site also contained several pits with fire-cracked stones.Some of the smaller pits were most likely used for metalworking activity, but it is less clear what the larger ones were used for.Two of the larger pits measured 1.5 × 2 m with layers containing charcoal, sand, and fire-cracked stones95.The pits have been suggested to represent charcoal production, however, considering that the site can be interpreted as a multipurpose hub for metalwork and trade with burial mounds, an urnfield, rock art and several stray finds nearby, the pits could just as easily represent activities related to ship building.
It is also important to note that to build and steam the planks of boats you also need the relevant tools.There are 810 simple shaft-hole axes registered in the county of Viken, 92 Bårdseth/ Sandvik 2007, 193-196. 93 Bårdseth/Sandvik 2007.94 Melheim et al. 2016. 95 Melheim et al. 2016, 59. most of these are located in the Østfold area (Fig. 16).The simple shaft-hole axes have been connected to clearing of land96 and would act as an important basic tool for felling trees.There have been few experimental studies of these axes but a study from 1969 does suggest that the axes were excellent for felling and cleaving trees97.It is noteworthy that the simple shaft-hole axes are distributed relatively evenly across the region while the metal axes (34 registered) are concentrated by the coast.This could potentially reflect a system where timber was exported from the interior through the river systems while the more precious metal axes were used for more finer woodworking in the shipbuilding process near the steaming pits by coast, for example, preparing planks.
The ability to build seafaring ships in this region could have an important comparative advantage.The extensive representation of boat motifs on the rock art, the great spread of axes near the coast and by inland rivers, combined with the region's connection to the inland and coast could potentially reflect a region where ship building served as an important part of the political economy and its accumulated wealth.

Discussion
We started this paper by addressing the general lack of evidence of the process of building boats in prehistoric Scandinavia, especially with regards to the Bronze Age.The period is characterized by long distance exchange of metals over vast areas in Europe.For instance, the regions in Scandinavia consumed large amounts of copper and tin that in turn were imported from far-off regions such as the British Isles, the Apline region and Iberia.98.To meet these demands, Bronze Age communities in Scandinavia must have made significant investments in the maritime forces and social relations of production, such as boats and crews capable of making lengthy sea voyages to secure metals99 and several boatloads of metals must have been transported between the metal production regions in the south versus the metal consuming regions in the north.In addition to this, several regional boat journeys within the Scandinavian sphere were necessary to exchange less prestigious materials such as tar, soapstone, slate, flint, and organic materials perhaps timbers, furs, and more100.Besides the few finds of real boats dated to the Bronze Age in Scandinavia we have a vast number of boats depicted on the rocks as well as the remains of large stone monuments, ship settings.Interestingly, these prehistoric remains occur in large numbers in the regions concerned by these case studies.
But what about the sites that shows more concrete evidence of boat building?In other world regions ethnographic and ethnohistoric data highlights the importance of steaming pits for the building of plank-built boats and other traditional watercraft.Other stone features associated with boat building in the ethnographic record include fire pits for hollowing out logs and for the melting of pitch needed for caulking and waterproofing.These stone features are often large and produce identifiable archaeological signatures, even when other evidence of boat building might be lacking in the archaeological record.
We contend that the features re-examined and reinterpreted as steaming pits in this paper might be regarded as evidence of these ethnographically documented features.In the case studies from Western Sweden and eastern Norway we argue that the examined features at these sites correspond to ethnographic descriptions of steaming and fireplaces used for repairing or building boats.Of special interest here are the pits that include stones affected by sever heat and a large amount of soot, charcoal or burnt wood at ancient leeward and seaside locations, dated to the Bronze Age.The presence of steaming pits at sheltered coastal sites fits well with the ethnographic analogies described above and is documented from numerous regions of Scandinavia.The pits of notable importance in this context lack any traces of food remnants.
For instance, the case from Tanum including 16 steaming pits dated to the Bronze Age.Thus, the site's beachfront and leeward placement at the foot of a steep hill and at the inlet of a large bay promote boat building.The wood examination showed that most pits contained pine (Pinus) charcoal and this kind of wood is well-suited for constructing boats, as well as for the processes of steaming, heating, and potentially producing tar.Overall, the idea supports the notion that these pits were created as a result of boat construction or repair.Finally, the postholes found at the site may indicate the presence of a rudimentary "naust", which is a type of boat house capable of accommodating a boat measuring approximately 8-12 metres in size.
As for the case in Tanum, the riverine area of Arlösa in Halland comprised steaming pits, filled with fire-cracked stones and charcoal, dated to the Bronze Age.Another case is the one in Borge, Norway located close to the coast, the steaming pits recorded here dated to the transition Early to Late Bronze Age.They did not contain any foodstuff or bones but held large amounts of fire-cracked stones and charcoal identified as broad-leaved deciduous wood such as oak, excellent for making both log and plank-built boats.Multiple woodworking tools such as shaft-hole axes have been discovered near the steaming pit sites, indicating the presence of craftsmanship in the vicinity that might be connected to the steaming pit sites.
In this context, it is crucial to acknowledge that in order to hollow out logs or construct planks for boats, one must possess the necessary tools and numerous of woodworking tools have been recorded in all of the coastal regions we have accounted for.Likewise, the tools needed for felling and preparing timber may also have been a necessity for the procurement of resin and tar, as may the steaming pits.
An alternate possibility is that some of these pits were used for the preparation of pitch for waterproofing boats, which is likely to have taken place parallel to boat building.Large amounts of pitch were needed for the caulking of plank boats and the heating of pitch would have required stone fire features similar to those documented in this paper.The wood species documented in many Scandinavian fire affected rock features also matches those that would have been used to produce tar giving further strength to this possibility.It should be noted that archaeological finds of pitch, and especially tradable pitch loafs, increases during the Bronze Age101.We suggest that this pattern is possibly associated with the increased need for pitch to waterproof sewn plank watercraft.
Why have previous investigations overlooked the possibility that these features were boat building sites?We hold that part of this problem is due to preconceived notions and epistemological paradigms that in turn has hampered the way archeologist has interpreted, or not simply looked at, this particular material evidence.The shore connected "cooking pits" or rather as we called them "steaming pits" could be seen as a typical example of this.First of all, we have the traditional functionalistic interpretation suggesting that they were meant for the preparation of food102.However, the functionalistic strand became later criticized by scholars influenced by a post processual ritualistic strand, rightfully arguing against this idea due to the lack of evidence of food remains in these features103, Although the latter strand fell into the same pit simply by ignoring the fact that some of these features and sites potentially could be remains of prehistoric boat building.In general, this pertains to the archaeological field that has historically neglected the study of the sea and instead concentrated solely on terrestrial investigations104.The main reason for this may be that the main thrust of European prehistory has followed a fundamentally terrestrial narrative and downplayed aspects related to boats and boat building.
We contend that much, if not most, prehistoric occupation was coastal, and seas or rivers provided the most important infrastructure for transport, exchange and communica-tion105.Thus, know-how about boats and boatbuilding must have had a profound impact for these societies and not least on their social organisation as indicated by ritual monuments and iconography.In this paper we have argued that some of the features that traditionally been defined as cooking pits could be re interpreted as a steaming pits or heating pits that in turn can be seen as traces of prehistoric boat building.We argue that refocussing archaeology to include a maritime perspective that attempts to identify and re-conceptualize archaeological contexts with a view towards boats and boat-building delivers a more accurate vision of prehistoric communities and their socio-economic activities.

Conclusion
The enigmatic pits, holding traces of charcoal and stones cracked by fire, have intermittently captured the attention of Scandinavian archaeologists over the past century.However, interpretations have often followed a familiar pattern, associating these structures with aspects of food-related practices, whether as functional facilities or representations of ritual feasts.This paper has aimed to present an alternative viewpoint to this prevailing consensus.By adopting a maritime perspective in our approach to these pits, we contend that at least some of them served as structures for steaming logs and constructing plank-built boats, and possibly also for producing tar during the Nordic Bronze Age.Comparing between ethnographic examples as well as archaeological case studies from and Bohuslän, Halland, and Østfold, we suggest that these features are important remains of boat building and maintenance activities which were central to the functioning of Bronze Age economies and lifeways.
The fact that these missing boatyards may have been hiding in plain sight drives home the second point that we have made throughout this paper; that a terrestrial paradigm still pervades throughout archaeological discourse.The identification of shore connected stone pits as "cooking pits" despite any material evidence of cooking or domes- tic activity is an excellent example of how this terrestrial bias can lead to clouded and potentially false archaeological interpretations.These misinterpretations can also affect broader anthropological theories, which still give primacy to terrestrial processes such as domestication and agricultural intensification as prime movers of social change.Breaking down this terrestrial paradigm might lead the identification of more unidentified maritime features that in turn could forward aspects of maritime migration, transport and exchange, as well as reveal alternative pathways to social complexity in our past.

Fig. 3 :
Fig. 3: Similarities in shape and building techniques between (top); rock art boat from Tanum dated to Early Bronze Age (1700-1500 BCE), compared with (bottom) parts of the Hjortspring boat dated to 350 BCE.Note: the arrows shows the corresponding parts of two different vessles.(After Bengtsson, B., et al., forthcoming).

Fig. 4 :
Fig. 4: Comparison between four Scandinavian Iron Age Boats (left) and (right) four ship-settings dated to the Bronze Age, demonstrating continuity in the shape and size of vessels from the Bronze Age to the Viking Age in Scandinavia.(drawing by Boel Bengtsson after Bengtsson et al., forthcoming).

Fig. 5 :
Fig. 5: Map showing the spread of shore-connected steaming pits from West Sweden and Norway during the Bronze Age.Map by Knut Ivar Austvoll.

Fig. 6 :
Fig. 6: Historical engraving dating to 1590 depicting Algonquian speaking people from present day North Carolina using fire to construct dugout canoes.Note the multiple uses of fire, both for felling trees and for hollowing them out.Engraving by Theodor de Bry.Modified from public domain image from Wikimedia Commons.

Fig. 8 :
Fig. 8: Map of Bohuslän coastline in about 1300-1100 BCE, reconstructed on basis of shore displacement data for each area.The distribution of rock art (red dots), cairns (black dots) and bronze finds (yellow dots) is also illustrated.After Ling 2014.Note the two sites with steaming pits discussed in this article are denoted by arrows.
pits are assembled in a linear formation, extending parallel to the coastline, with one to two rows (Fig.11-12).At the very centre of the site a substantial post hole was recorded that measured 0.48×0.40metres, Petersson60 argue for the notion that it could have been the remains of a large totem pole.In this context is tempting to consider the Gerum rock 60 Petersson 2009.

Fig. 9 :
Fig. 9: Map of the Tanum area in the Bronze Age showing the shoreline about 13-14 m.a.s.l.Note the site Tanum 1835 is denoted by a red circle.Red dots = rock art sites; white dots = cup mark sites; black dots = cairns; large buff triangles = settlement finds (carbon dates, ceramics, or other features) dated to the Bronze Age; small buff triangles = indicative settlement sites from the Bronze Age; yellow dots = bronze items; blue diamonds = daggers from LNI-EBA II; white flashes = sickles from LNI-EBA II (After Ling 2014)

Fig. 14 :
Fig. 14: Map of the site with the "steaming pits" at the site Tanum 1835 (L 1967: 4174), showing the close relation between the site and Late Bronze Age shore line.

Fig 16 :
Fig 16: Map showing the distribution of pits with fire-cracked stones and axes (metal and simple shaft-hole axes) in Østfold.Map by Knut Ivar Austvoll.

Fig. 17 :
Fig. 17: Map showing a section of Østfold with steaming pits from the Bronze Age.Sea level set to 17 m asl, based on an approximate level during the Bronze Age.