There is much that we do not know about these putative immigrant farmers and about their relationship with the indigenous Mesolithic communities. There is evidence that the Mesolithic lifestyle continued at least until the opening centuries of the sixth millennium BP, and this is confirmed by recently-obtained radiocarbon dates on human and boar remains from the Cnoc Coig (CANMORE ID 37818) shell midden, which lie within the first quarter of that millennium (Charlton et al. 2016, and see also Milner 2010). The radiocarbon dates from Carding Mill Bay (CANMORE ID 22947) midden start from 6180-5740 cal BP (4230-3790 cal BC) and continue through the entire 6th millennium BP (4th millennium BC; Connock et al. 1992), while human bones of 'Neolithic' date were deposited in the Mesolithic midden at Raschoille cave (Milner and Craig 2009, Bonsall et al. 2012).
The chronological analysis undertaken by Wicks et al. (2014) support the notion of Mesolithic-Neolithic overlap, most starkly illustrated at the Mesolithic site of Storakaig (CANMORE ID 304908) on the Isle of Islay (Figure 39) that has dates that overlap with both the latest dates from the Oronsay middens and the earliest Neolithic in this part of Argyll (Figure 44). Potential chronological overlap or, at least, close temporal succession of the events taking place in these locations is especially interesting because Storakaig (CANMORE ID 304908) is a 'classic' Mesolithic site and would have sat comfortably within the residential period of settlement. Its chipped stone assemblage contains some large blades and retouched artefacts that are generally considered diagnostic of Neolithic assemblages but which are scarce in Argyll (Wicks et al. 2014). At Storakaig (CANMORE ID 304908), these Neolithic-like artefacts are scattered across the site and are indistinguishable from the diagnostically Mesolithic artefacts in their condition and patination within a tightly clustered set of radiocarbon dates (Wicks et al. 2014).
Figure 44: Overlap of dates from Storakaig with those of the Earliest Neolithic on the Isle of Islay © copyright
The radiocarbon dates from both the Oronsay sites and Storakaig (CANMORE ID 304908) have a significant overlap with the dates of the Clyde cairns, including Port Charlotte (CANMORE ID 37313) chambered cairn on Islay (Henshall 1972: ILY 1, Harrington and Pierpoint 1980), which yielded three preconstruction dates from the occupation layer under the cairn 5930-5590 cal BP, 5900-5580 cal BP and 5590-5050 cal BP (3980-3640 cal BC, 3950-3630 calBC and 3640 - 3100 cal BC. Two dates from inside the chamber of the cairn were 5460-4960 cal BP (3510-3010 calBC) and 5590-5310 cal BP (3640-3360 calBC). Very similar dates come from Newton (CANMORE ID 37769), c.5km northwest from Storakaig (CANMORE ID 304908), where two pits containing Neolithic pottery produced dates of 5890-5590 cal BP (3940-3640 cal BC) and 5750-5470 cal BP (3800-3520 cal BC) (McCullagh 1989). Although we are dealing with overlaps between substantial date ranges, which by no means prove overlap in the activities at these Mesolithic and Neolithic sites, these nevertheless provide a significant cluster of dates spanning the transition in a narrow geographic proximity.
Neolithic activity is also evident at Bolsay (CANMORE ID 37342 AND CANMORE ID 37347) , one of the most extensive Mesolithic sites on Islay. This is situated 2km to the northwest from Port Charlotte (CANMORE ID 37313) chambered cairn and an equidistance from the chambered cairn of Slochd Measach (CANMORE ID 37335) (the 'Giant's Grave'), located to the west of Bolsay (CANMORE ID 37342 AND CANMORE ID 37347) (Henshall 1972), Figure 45. The excavation at Bolsay (CANMORE ID 37342 AND CANMORE ID 37347) recovered 329,667 pieces of chipped stone, including 7000 microliths, and was interpreted as a frequently-visited hunting camp, providing a significant 'place' for Mesolithic people who returned to it repeatedly for over millennia. Mesolithic occupation is represented by an in situ horizon sealed by colluvium, which was disturbed by ploughing. This colluvium contained a huge number of artefacts of narrow blade technology, which is conventionally entirely associated with the Mesolithic period, along with small numbers of Neolithic and Bronze Age artefacts, including the fragment of a polished stone axehead.
Figure 45: Mesolithic and Neolithic sites on Islay referred to in the text © copyright
From ten Bolsay (CANMORE ID 37342 AND CANMORE ID 37347) C14 dates only three belong to the Mesolithic, providing two activity events centred on 8155 cal BP and 7650 cal BP (6205 cal BC and 5700 cal BC) and thus predating the activities at Storakaig (CANMORE ID 304908) and Oronsay. However, renewed activity at the site in the Early to Middle Neolithic is evident by three C14 dates with ranges between 5590-5320 cal BP (3640-3370 cal BC), 5580-5070 cal BP (3630-3120 cal BC) and 5300-4880 cal BP (3350-2930 cal BC) (Mithen, Lake and Finlay 2000), even though the diagnostic Neolithic artefacts are a tiny proportion of the whole. The Bolsay (CANMORE ID 37342 AND CANMORE ID 37347) site in unquestionably a palimpsest of activity from an extensive chronological range, but whether this is one of clearly differentiated events separated by extensive periods of time, or a continuous flow of similar types of activity that nevertheless falls into different cultural periods as conventionally defined remains unclear. The fact that Neolithic lithic material is not only found on a site that had been frequented during the Mesolithic, and within the same archaeological contexts raises the question of what exactly constitutes 'Mesolithic' and 'Neolithic' settlement remains in western Scotland (Armit and Finlayson 1992).
The population density for both indigenous and putative immigrant groups might have been sufficiently low that it is possible that they had successfully co-existed in relative proximity of each other for several generations, no doubt being aware of each other. The fragmented nature of the west coast of Scotland and the adjacent islands offered such diverse subsistence opportunities for the hunter-gatherer groups that the introduction of the initial small scale farming in this landscape may not have imposed any immediate threat to their way of life (Milner 2010). Nevertheless, a process of acculturation - or simply Mesolithic extinction - took place, perhaps swiftly, with the demise of the purely hunting and gathering way of life. This is starkly illustrated in the isotopic and lipid evidence relating to human diet, with no individuals having a 'Mesolithic' dietary signature being known to post-date the aforementioned Oronsay shell midden individuals. The interpretation of such dietary data remains in contention, with an invaluable review by Sheridan and Pétrequin (2014).