The sandy beds of the Cagayan River make it suitable for shellfish to thrive. Archeological studies confirm that the gathering of clams in this part of Cagayan dates back to the Neolithic age.

There are several shell middens in barangays of San Lorenzo, Catugan, and Alaguia, Sta. Maria, Catayauan, Magapit, and Bangag. In Magapit, the shell middens are at the top of the hill. The deposit is 800 meters from the riverbank and has a panoramic view of the Cagayan River. Bangag shell midden sits on the Magapit site. This site has a deposit of 100 meters in diameter and 2.8 meters (9 feet).

About four (4) kilometers from Lal-lo are the Catayauan shell middens. The deposit extends about 500 meters long, 100 meters wide, and two meters deep. Not so far from Catayauan is the Santa Maria shell midden deposits. The middens are located upstream Cagayan River with a distance ranging from 30 to 50 meters that stretches up to one (1) kilometer. Other locations include the riverbanks of San Lorenzo, Catugan, and Alaguia. Accompanying the discovery of shell middens in these sites is the unearthing of various stone tools, pottery sherds, and earthenware. These indicate Neolithic Age when the early people started domesticating animals, planting crops, and developing craftsmanship by making tools, pottery, and other home implements. These are critical findings in establishing the presence of communities in pre-historic Cagayan.