Wallace Line to the west of the Philippines. Wallace's studies in Indonesia demonstrated the emerging theory of evolution, at about the same time as Joseph Dalton Hooker and Asa Gray published essays also supporting Darwin's hypothesis. Understanding of the biogeography of the region centers on the relationship of ancient sea levels to the continental shelves. Wallace's Line is visible geographically when the continental shelf contours are examined; it can be seen as a deep-water channel that marks the southeastern edge of the Sunda Shelf which links Borneo, Bali, Java, and Sumatra underwater to the mainland of southeastern Asia. Australia is likewise connected
Front line Front line A front line (alternative forms: front-line or frontline) in military terminology is the position(s) closest to the area of conflict of an armed force's personnel and equipment, generally referring to maritime or land forces. When a front (an intentional or unintentional boundary) between opposing sides form, the front line is the area where the armies are engaged in conflict, especially the line of contact between the opposing forces. In a military conflict, then, when facing the front line, you face the enemy. All branches of the U.S. armed services use the related technical terms, Forward Line of Own