Teeth, Beads, and Strata: Finding the Ancient Inhabitants of Callao Cave

By Angela Masongsong

Human evolution is an expansive narrative that is still out of our grasp. Southeast Asia, in particular, continues to baffle archaeologists trying to study how prehistoric people moved. Islands within the region are bounded by oceans and seas with strong currents discouraging migration. How these ancient people moved from island to island is still up for debate.

Who knew that the discovery of a “hobbit-like” human species will change the game? In 2004, the Homo floresiensis was discovered on an isolated island in Indonesia. This meant that early humans within the region indeed moved around. For the archipelagic Philippines, this means that the hunt for traces of these prehistoric people is on.

Inside the Caverns

Situated in Cagayan, the Callao Cave complex is a spectacle on its own. Some of its numerous chambers have collapsed roofs that let light stream inside the cave. Well-formed speleothems and well-formed rock features emphasize the beauty of this karstic environment.

Aside from its natural beauty, Callao Cave is home to the prehistoric inhabitants of these islands. Dr. Armand Mijares of UP Diliman and his team found evidence of human activity back in 2003 but did not excavate beyond 2 meters. It was previously believed that hominid activity did not occur past this point.

However, the Indonesian discovery encouraged Dr. Mijares and other archaeologists to dig deeper.

Layers and Layers

Callao cave has complex geology behind it due to its karst setting. Aside from limestone, deposits of breccia and other volcanic sediments are present. Layers of deposited sediment or strata and other features can tell us the story of how an area came to be. In this case, it can also tell us about when prehistoric people inhabited a certain location.

Using a method called soil micromorphology, Dr. Mijares and his team obtained samples of soil and rock layers. Excavation itself can show us macroscopic evidence of human activity. Artifacts such as earthenware sherds, beads, and tools can be seen macroscopically from the section.

There are, however, traces that can’t be seen using the naked eye. Samples are cut into thin sections and viewed under a petrographic microscope. From this, small but significant evidence such as the burning of charcoal and small flakes from tools can further confirm the presence of prehistoric hominids.

From a 2017 publication, at least 3 time periods of human activity in Callao Cave were confirmed — farther into time than previously speculated. It was also discovered that these humans existed roughly a few millennia apart. In 2019, the landmark discovery of the Homo luzonensis implied a greater diversity of ancient humans within Southeast Asia.

Turning Back Time

Callao cave is valued due to its archaeological, geologic, and natural significance. It is also an important piece in unlocking Southeast Asian prehistory. In an article from National Geographic, Dr. Mijares said: “I’m very proud, because as a Filipino and Southeast Asian, we tend to be on the periphery of this debate. Now, we can be actively engaged in the debate because our areas — our sites — are now recognized”.

Questions about our origin, heritage, and islands are still far from being answered. What else can we do but dig deeper?


Mijares, A. S. (2017). Understanding the Callao Cave Depositional History. terra australis 45, 125.

Greshko, M., & Wei-Haas, M. (2019, April 11). New species of ancient human discovered in the Philippines. Retrieved February 19, 2021, from https://www.nationalgeographic.com/science/2019/04/new-species-ancient-human-discovered-luzon-philippines-homo-luzonensis/

Fleming, N. (2019, April 10). Unknown human relative discovered in philippine cave. Retrieved February 19, 2021, from https://www.nature.com/articles/d41586-019-01152-3



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