Associated time intervals range from c. 25,000 to 18,000 BP, but broadly centre upon 21,000 BP 10,11. Within Switzerland, the last glacial advanced occurred sometime after 30,000 BP 1. Local geomorphological evidence and speleothem δ 18 O minima suggest maximum ice extent may have been reached between 26,500 and 22,000 BP, while the onset of rapid ice decay started by c. 19,000 BP 1,2,12,13. Climate models and proxy data indicate a cold dry climate existed north of the Alps during this time period, while the formation of Alpine speleothems suggests warm air masses from the south delivered precipitation to the northern Alpine slopes 2,7,8. North of the mountains, continuous periglacial permafrost conditions existed, with tundra and steppe landscapes dominated by graminoid and forb vegetation 14,15. Nonetheless, the Alpine LGM was punctuated by sub-millennial climate fluctuations related to changing temperature and precipitation regimes, which influenced local environmental conditions and ice extent 2,16-18. Within Switzerland a positive excursion in speleothem δ 18 O occurred between 23,230 ± 37 BP and 22,759 ± 47 BP 2 , linked to changing precipitation patterns, and this appears to have coincided with a phase of recession in the Alpine ice sheet 18. The timings of these local environmental changes matches with the Greenland warm period of GI-2 (23,290 ± 596 BP to 22,850 ± 573 BP 9), within dating uncertainties. This suggests that the warming in Switzerland may have been associated with continental-scale processes. The Greenland record of GI-2 is interrupted by a brief climatic cooling lasting around 200 years (Greenland Stadial 2.2) and centring on approximately 23,100 BP 9. The expression of this event in the Swiss record is less clear but may occur between 22,971 ± 46 BP and 22,888 ± 50 BP 2. The link between GI-2 and human activity in Switzerland has previously been postulated 6. However, chronological resolution is currently poor and archaeological evidence is sparse. The dated cut-marked reindeer (Rangifer tarandus) bones from Kastelhöhle-Nord (n = 3) and Y-Höhle (n = 1) represent the only directly dateable archaeological evidence from this time period in Switzerland 5,6. Both cave sites are located within 10 km of one another, on the northeastern edge of the Jura Mountains, less than 50 km from the maximum ice sheet extent. Lithics found in association with the reindeer bones at Kastelhöhle-Nord have been attributed to the Badegoulian/Early Magdalenian 4,6 , a Late Upper Palaeolithic culture found in western-central Europe. In contrast, the cut-marked reindeer bone from Y-Höhle was found in a secondary context with no association to other archaeological remains 5. Lithics of Badegoulian character are also found in Germany (Wiesbaden-Igstadt, Rhineland, and Gera-Zoitzberg, Thuringia) 6,19 , while broadly contemporaneous evidence of human activity is also present in southern Germany (Mittlere Klause), and further east in Austria (Kammern-Grubgraben and Langmannersdorf), the Czech Republic (Stranska Skala IV) ...