Gwynnie gets to spend part of her summers protecting a unique forest preserve in the Sierra Nevada range in a valley which was once used in the summers by the Martis Indians (see The Martis Indians: Ancient Tribe of the Sierra Nevada by Willis Gortner). According to Gortner and others, the Martis occupied the region from a time of global cooling and increased rain around 2000 BC to about 500 AD, when the climate again changed and became drier. Also at about that time, more aggressive tribes like the Paiutes had developed the bow and arrow which required obsidian not found in the area. There could have been conflict with the Paiutes or the Washoe to the East, or with the gentler gatherers, the Maidu, to the North. It was the Maidu which occupied the valley after the Martis departed to an unknown fate.
The Martis Complex left their mark on the land, however, in the form of what scholars call “High Sierra Abstract-Representational petroglyphs” as shown in the picture. All petroglyphs are on horizontal or sloping granite bedrock, with none on cliff faces or boulders, and each site has an unimpeded view of at least three peaks.