Note: since these have already been discussed by the present author in some detail in previous publications (most recently Sheridan 2012a, and see also Sheridan 2004a), the reader is recommended to consult those for a fuller discussion. It is clear that once both sets of putative immigrant farming groups (i.e. the Breton ‘strand’ and the ‘Carinated Bowl Neolithic strand’) became settled in Argyll and Bute, they flourished and spread. This is seen, for example, in the construction (probably around 3600 BC) of a bigger, ‘better’ passage tomb at Achnacree (CANMORE ID 23223), not far from Achnacreebeag (CANMORE ID 23253) (Henshall 1972, 355-7), and the expansion of passage tomb building to the Hebrides, the NW and NE mainland of Scotland, and the Northern Isles (Sheridan 2004b; 2014a). It is also seen (with regard to the ‘CB Neolithic’) in the construction of the simple stone chamber at Ardnadam (CANMORE ID 40746), Mid-Argyll (Henshall 1972, 331, 333) and, subsequently, of ‘Clyde’-type chamber tombs in Argyll and Bute (eg Nether Largie South (CANMORE ID 39460): ibid, 338-40 and Cladh Andreis (CANMORE ID 22360) on the Ardnamurchan peninsula: Harris et al. 2014). Both forms may indeed be present as sequential phases in the construction of the chamber tomb at Blasthill (CANMORE ID 38677) on the Kintyre peninsula (Cummings and Robinson 2015a and b). These represent translations into stone of the timber funerary monument tradition brought by the earliest CB Neolithic communities, and to judge from the currently-available dating evidence, the ‘Clyde cairn’ format was being constructed by the mid- to late-38th century BC, with clear evidence for use during the 37th and 36th centuries BC. Other ‘CB Neolithic’ constructions include the cursus monument at Upper Largie (CANMORE ID 39486) in Kilmartin Glen (Sheridan 2012a, 170).
Interaction between the ‘Breton’ and ‘CB Neolithic’ communities is abundantly clear from the sharing of ceramic designs, with a distinctive, fluted or burnished tall-necked carinated bowl type of pot, probably dating to the 36th century BC, being found both in the Achnacree passage tomb (CANMORE ID 23223) and in the Nether Largie South (CANMORE ID 39460) Clyde Cairn, for instance (ibid, 170) (Figure 54). This type of pot has also been found on Balloch Hill (CANMORE ID 38340), near the tip of the Kintyre peninsula, in what may well be a domestic context (Peltenburg 1982, Figure 12). There is also abundant evidence for the exchange of ideas, designs, objects and probably also people between Argyll and Bute and Ireland for most of the Neolithic period, as seen for example in ceramic similarities and in the sharing of the ‘Clyde cairn’ constructional tradition (which is expressed as ‘court tombs’ in Ireland) (Sheridan 2004a). Further afield, at Clettraval (CANMORE ID 10196) on North Uist, a dramatic example of the melding of the two ancestral Neolithic traditions can be seen in the design of a chamber tomb that combines elements of both the passage tomb and Clyde cairn traditions (Henshall 1972, 506-511).
Relatively little is known about developments between c 3500 BC and c 3000 BC in Argyll and Bute (Sheridan 2012a, 171) even though palynological evidence from Kilmichael Glen indicates a strong signal for barley cultivation from 3600 BC (Tipping et al. 2011, 161), and there is evidence for the continuation of extensive exchange networks, such as had been involved in the transportation of the Antrim porcellanite axehead – and perhaps also its associated wooden haft – found at Shulishader (CANMORE ID 71061), Lewis, during the second half of the fourth millennium: Sheridan 1992. It is during this period that farming communities were flourishing in the Outer Hebrides.