Empirical Studies
Secure Phylogenetic Attachment, Dyadic Trauma, and Completion Across the Life Cycle
Joseph P. Riordan, Abi Blakeslee, and Peter A. Levine

Research
The Somatic Experiencing Trauma Institute has published some interesting research related to Somatic Experiencing.

The very structure of trauma, including hyperarousal, dissociation, constriction and helplessness, is based on the evolution of predator/prey survival behaviours.
Dr. Peter Levine