Because of differences in craniofacial morphology and dentition between the earliest American skeletons and modern Native Americans, separate origins have been postulated for them, despite genetic evidence to the contrary. We describe a near-complete human skeleton with an intact cranium and preserved DNA found with extinct fauna in a submerged cave on Mexico's Yucatan Peninsula. This skeleton dates to between 13,000 and 12,000 calendar years ago and has Paleoamerican craniofacial characteristics and a Beringian-derived mitochondrial DNA (mtDNA) haplogroup (D1). Thus, the differences between Paleoamericans and Native Americans probably resulted from in situ evolution rather than separate ancestry.

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The nearl)-complete, well-preser_,ed skeleton of a Paleoarnerican male was found by chance near Kennewick, Washington, in I996. A though analysts was quickly suspended by the U.S. government, initial osteological, archaeological, and geological studies provide a ghmpse into the age and life of this individual. A radiocarbon age of 8410 _ 60 B.P., stratigraphic position in a wideIy-dated alluvial terrace, and an early-Cascade sty!e projectile point healed into the peh,is date the find to the late Early Holocene. Initial osteological analysis describes the man as middle-aged, standing 173.1 +_3.6 cm tall and weighing approximate,! 3 76-75 kg. I-lealthv as a child he later sufjered repeatedly from injuries to his skull, left arm, chest, and hip, in addition to minor osteoarthr tis and periodontal disease. His physical features, teeth, and skeletal measurements show him to i be an outlier relative to modern human populations, but place him closer to Pacific 1slanders and Ainu than to Late Prehistoric Amerinds or an 3 other modern group. Despite his umque es_ relative to modern peoples, he is not significantly different fromother Paleoamerican males in most characteristics.Elesqueletopreservado)casicompletodeun ombrepaleoamericanofuedescubiertooorcasualidadcercadeKennewick, Washingron, en 1996. Aunque el andlisis fue rapidamente suspendido por el gobierno de los Estados Unidos. estudios osteol6gicos, arqueoldgicos, y geol6gicos iniciales proveen informaci6n sobre la edad 3' vida de este individuo. Una edad radiocarb6nica de 840 ± 60 A.P., la posicidn estratigrdfica en una terraza aluv a de edad conocida, y una puma de proyectil de estilo Cascade temprano en la pelvis datan este halla=go aI Holoceno temprano. El andlisis osteol6gico inicial describe a un hombre de edad media. de173.1 +-3.6 cm de alto 3 de 70-75 kg de peso. Sus rasgos fisicos dientes, 3' mediadas esqueletales lo ponen rods cerca de los habitantes de las islas pacfficas que de los amerindios prehistdricos lardfos o de cualquier otra poblaci6n moderna. Sano en su juvemud, el sufrl6 heridas en su crdneo, brazo izquierdo, pehc9 v cadera, ademds de osteoartrltis y enfermedad periodontal. No se ha determinado la causa de su muerte, pero sus hueso proveen un visidn rara y pasajera de la vida de los paleoamericanos y sugiere pregunta_ sobre la complejidad y el tiempo del poblamiento de Amdrica.

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An understanding of the response of a fluvial system to past climatic changes is useful for predicting its response to future shifts in temperature and precipitation. To determine the response of the Columbia River system to previous climatic conditions and transitions, a well-dated sequence of floodplain development in the Wells Reservoir region was compared with the paleoenvironmental history of the Columbia River Basin. Results of this comparison indicate that aggradation episodes, occurring approximately 9000-8000, 7000-6500, 4400-3900, and 2400-1800 yr B.P., coincided with climatic transitions that share certain characteristics. The inferred climates associated with aggradation had at least moderate rates of precipitation that occurred mainly in winter coupled with moderate winter temperatures. Such conditions would have resulted in the buildup of snowpacks and a high frequency of rain-on-snow events. The warming and precipitation increases predicted for the Pacific Northwest under most CO2-doubling scenarios are likely to repeat these conditions, which could increase the frequency of severe, sediment-laden floods in the Columbia River Basin.

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