A summary of research in the southern Channel Islands of California is presented. This research shows that these islands have been occupied for nearly 10,000 years. Residential structures and the distribution of a type of marine shell bead suggest that sedentism and a regional interaction sphere arose in this region as early as 5,000 years ago. Additional information is presented on chronological trends and the impact of humans on nearshore ecosystems, including fish and shellfish populations. These data are leading archaeologists to reassess the age and origins of marine cultural traditions in southern California.