The bright sun makes its appearance over Rattlesnake Rock, yet again, bringing warmth again to the Grinding Rock. This old piece of sandstone rolled down here as Rattlesnake Rock pushed up, during the Eocene Epoch -- 40 or 50 million years ago, after the dinosaurs, before humans. Later, a band of the First People settled nearby. I don't know, but this is the picture I have: women sitting on top of the rock, mortar in hand, grinding acorns and perhaps other plants. Children and others roaming through the oaks, gathering the acorns and carrying them to the rock. Lots of gossip and community. Several grinding holes are still visible on top of this boulder. Jasper Ridge Biological Preserve, Trail a near the Herb Dengler Trail. 7/17/2022, 8:58 am.