Origins of the First Californians

Transcription

1 Setting the Stage for the Peopling of the Americas Origins of the First Californians John R. Johnson Anthropology 131CA Mal ta Peopling of Siberia was episodic between 35,000 and 15,000 years ago. Middle Upper Paleolithic, 33,000 to 24,000 BP, people pushed further north. Last Glacial Maximum (LGM), 24,000 to 21,000, people retreated southward to refugia. Different technologies, earliest microblades in northern Japan (not at Mal ta) Late Upper Paleolithic (post-lgm) high tool diversity, first evidence for domestic dogs, medium to largebodied game are focus. Three Stage Colonization Model for the Peopling of the Americas The Siberian Connection 1. Divergence from ancestral Asians abt. 40,000 years ago. 2. Occupation of Beringia between 30,000 to 16,000 years ago, population isolated. 3. Expansion into the Americas approximately 16,000 years ago. 4. Effective population size of Proto-Amerinds estimated at 6,000 to 10,000 individuals Questions regarding migration: What were the routes traveled? When was migration possible? North American Late Pleistocene Fauna ca. 14,000 yrs. BP 1

2 How Bad Was It? Clovis Points End Pleistocene ( ~13,000 ka) - the last catastrophic faunal extinction in geologic past Coincides with the deglaciation between the last glacial episode and the present Holocene interglacial Timing of the extinctions are well constrained between the end of last glacial episode and the beginning of the Younger Dryas (~1,500 yrs), following the Clovis human occupation Theories for the Cause of this Extinction Human overhunting - isotopic studies suggest a more diverse diet - diverse hunting strategies needed to exterminate such a wide variety of taxa - specialization in big game hunting rare - game rich landscapes with few people - other taxa clearly exploited (e.g. bison) actually survived the extinction Climate change - Mammal extinction is coincident or close to abrupt Younger Dryas cooling event - Within the context of late Quaternary climate history abrupt cooling not an uncommon event occurring frequently over last 80 kyrs - Younger Dryas cooling event less severe compared to earlier events in the Quaternary with no associated extinction event Combination - overhunting/climate change Black Mat Distribution of early Younger Dryas Age Santa Rosa Island Black Mats (from Vance Haynes, 2005) 2

3 Black Mat above Clovis/Extinction layer Evidence for an Impact Event? Titanium-rich Magnetic Spherules Algal Mat Top Clovis ~13,000 ka extinction ET debris Glass-like Carbon Murray Springs, AZ, photograph provided by A. West Carbon Spherules The Younger Dryas Boundary (YDB) Cosmic Impact Hypothesis Where is the Crater? Daisy Cave Firestone and West

4 Bathymetic Map of Gulf of St. Lawrence Corossol Crater, Gulf of St. Lawrence Articulated pygmy mammoth skeleton discovered in

5 Mouth of Arlington Canyon, Santa Rosa Island Excavations by Phil Orr, 1960 Arlington Man s bones in situ,

6 Stratigraphic Location of Human Bone Locations of Dated C-14 Samples Sample No. AS AS AS AS AS AS C-14 Samples Collected in 2001 Material/Provenience Sediment above "Black Band" Sediment near top of "Black Band" Sediment near bottom of "Black Band" Charcoal immediately above layer with human bone Charcoal beneath layer with human bone Charcoal from lowest stratum sampled Lab No C-14 Age (B.P.) 9,985 ± 40 10,315 ± 40 10,725 ± 40 11,250 ± 40 11,580 ± 45 11,640 ± 40 Approx. Calendar Years (B.P.) 11,300 12,200 12,900 13,200 13,500 13,800 GPR survey quadrants, June 2005 Datum A B C 6

7 Landscape reconstruction of the Arlington Springs vicinity based on GPR survey Quadrant C Quadrant B Quadrant A Scott Newhall and Doug Hechter with Scaled Sediment Core Poster 7

8 Application of Sea Level Curve to the Arlington Springs Sedimentary Record Younger Dryas Black Layer Pebble Layer Triplet Younger Dryas Black Layer Just Beneath YDB Arlington Man & Rodent Bone Bed Below Arlington Man Layer Dated Layers from Lower Strata in Sediment Cores AMS 14 C Dating of Late Pleistocene/Early Holocene Sediments at Arlington Springs 11,000 12,000 13,000 14,000 15,000 16,000 Johnson et al., 2007 Calendar Years Before Present (2 sd) 8

9 Arlington Canyon Late Pleistocene alluvium (Cal BP 13,130 to 12,800) Date from piece of pine wood (Yellow pine group) Arlington Canyon (AC-003) Carbon Spheres Magnetic Spheres & Disks Courtesy of Douglas Kennett, UO Images of Carbon and Metallic Spheres from Arlington Canyon Late Pleistocene Alluvium AC-003 Carbon Spherules Nanodiamonds TEM Image Reticulate Interior Diamond Diffraction Pattern Photos courtesy of Doug Kennett and Allen West Courtesy of Douglas Kennett, UO Summary - Arlington Springs The Channel Islands were connected as a single landmass in the late Pleistocene, but were separated from the mainland. The stratigraphy on Santa Rosa Island is largely undisturbed by bioturbation and other soil mixing processes. GPR aided in reconstructing the ground surface during the Younger Dryas Period, because of the change in stratigraphy caused by the black layer. The YDB at Arlington Springs has been dated between 12,900 and 12,200 Cal BP. Arlington Man s skeletal remains were recovered from a period of alluvial fill that dates to about 13,000 to 13,200 years ago, where some chert microflakes have also been discovered. Initial attempts at sampling the YDB at Arlington Springs yielded very few carbon spherules but some glass-like carbon. A second location (upcanyon) was discovered that dated to the beginning of the Younger Dryas that yielded abundant carbon spherules and pollen indicative of a pine-cypress forest that disappeared at the end of the Pleistocene. Abundant evidence of an extinct species of Deer Mouse was present before the Younger Dryas and disappeared along with the pine-cypress forest. 9