5.3.1 The chronological pattern of human activity

Establishing the chronology of human activity and an indication of population levels, in either relative or absolute terms, are key research questions for any period of archaeological study. For the Mesolithic of western Scotland, Wicks and Mithen (2014) undertook this task by adopting the activity event approach for all 32 radiocarbon dated Mesolithic sites in western Scotland, as available at the time of study. These had provided 227 radiocarbon dates. When those dates were screened to remove any that appeared unreliable or fell outside the defined chronological range of the Mesolithic the sample was reduced to 137, 69% of which are from Argyll. The activity event analysis identified 74 Mesolithic activity events, occurring at the 32 sites. The majority of sites were characterised by a single activity event, often because there was no more than a single reliable radiocarbon date. Recent fieldwork and dating programmes allows a further 26 radiocarbon dates to be added to the sample used by Wicks and Mithen (2014). Twenty-three of these dates came from Creit Dubh (Isle of Mull) and three from Rubha Port an t-Seilich (CANMORE ID 98306) (Isle of Islay; Mithen et al. 2015), providing an additional four activity events (three and one at the sites respectively). One further activity event located at Rubha Port an t-Seilich can be added. This is represented by a small collection of chipped stone artefacts with technological and typological characteristics of the Late Glacial rather than Mesolithic and dated by association with tephras to c. 12,000 BP (Mithen et al. 2015).

The chronological distribution of those 78 activity events by 400-year time steps throughout the Mesolithic period is presented in Figure 31. More than three quarters (77%, n = 16) of these events were located within Argyll. The first activity event is dated to c. 12,000 at Rubha Port an t-Seilich (CANMORE ID 98306), and hence formally placed within the Late Glacial and Palaeolithic period. There is no more evidence of activity within either Argyll or western Scotland in general until c. 10,230 cal BP at Creit Dubh on the Isle of Mull. There are no further documented activity events for c. 800 years, but as from c. 9400 cal BP there is a gradual and then a steep increase in their number. They reach a peak in the time-period between 8600-8200 cal BP with 25 activity events, located between Northton on the Isle of Lewis in the north and Rubha Port an t-Seilich (CANMORE ID 98306) on the Isle of Islay in the south. This is followed by a dramatic decline in the number of activity events, until there are only three activity events in the time period 7800-7400 cal BP, located at Bolsay (CANMORE ID 37342 AND CANMORE ID 37347) and Rockside, both on the Isle of Islay, and at McArthurs Cave (CANMORE ID 23066) near Oban. The number of activity events begins to increase again after 7000 cal BP, reaching 10 in the time period 6200-5800 cal BP. Their location is heavily concentrated on the tiny island of Oronsay and adjacent islands of Colonsay and Islay, although there is a single event at An Corran on the Isle of Skye. Activity events then decline in number and then cease at the end of the defined Mesolithic time period.

Figure 31: Histogram of activity events in western Scotland between 15,000 cal BP and the start of the Neolithic © copyright

The 18 non-Argyll activity events within this distribution are spread throughout its geographical range, although having a limited chronological presence (a single activity event) after 7000 cal BP. As such, the pattern for Argyll is not significantly different for western Scotland as whole, other than its apparent locus for settlement towards the end of the Mesolithic. Figure 32 represents the same data using a summed calibrated probability distribution (SCPD). These are increasingly used in archaeology as a proxy for human population levels (Williams 2012), even though the use of radiocarbon dates in this way has been argued to be problematic (eg Sheridan and Pétrequin 2014). The SCPD for Mesolithic Scotland increases the degree of bimodality of the activity event distribution, making both the rise and fall of human activity/population on either side of 8200 cal BP more intense.

Figure 32: Climate curve (GICCO5 ?18O isotope curve), sea level change, vegetation history from Loch an t-Sagairt, Isle of Coll and summed calibrated probability distribution of human activity in western Scotland between 12,000 cal BP and the start of © copyright

It is not possible to estimate the size of the population directly from the archaeological evidence. Estimates based on ethnographic analogies range from one to nine persons/100Km2 (Smith 1992; Gamble 1999). If we take western Scotland to encompass approximately a third of Scotland's entire landmass of c. 79,000 Km, then the Mesolithic population of western Scotland may have varied between c. 260 and 2370 people. As indicated in Figure 31, the chronological distribution of Late Glacial and Mesolithic activity can be divided into five temporal phases, each of which pose specific research questions.