Sibutu Passage is a deep channel some 18 miles (29 km) wide that separates

Borneo Borneo (; id, Kalimantan) is the third-largest island in the world and the largest in Asia. At the geographic centre of Maritime Southeast Asia, in relation to major Indonesian islands, it is located north of Java, west of Sulawesi, and ea ...

from the Sulu Archipelago. It has a deep sill allowing entry of deep water into the Sulu basin while connecting the Sulu Sea with the Sulawesi Sea that feeds from the

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the contin ...

by the

Mindanao Current The Mindanao Current (MC) is a southward current in the western Pacific Ocean that transports mass and freshwater between ocean basins. It is a low-latitude western boundary current that follows the eastern coast of the Philippine island group a ...

. Although H. Otley Beyer argued in favor of a settlement of the Philippines across

land bridge In biogeography, a land bridge is an isthmus or wider land connection between otherwise separate areas, over which animals and plants are able to cross and colonize new lands. A land bridge can be created by marine regression, in which sea leve ...

s during the last ice age, modern

bathymetric Bathymetry (; ) is the study of underwater depth of ocean floors (''seabed topography''), lake floors, or river floors. In other words, bathymetry is the underwater equivalent to hypsometry or topography. The first recorded evidence of water d ...

soundings have shown that the centers of the Sibutu Passage and the Mindoro Strait are both deep enough that they probably still existed at that time, although the Sulu and other

Philippine Islands The Philippines (; fil, Pilipinas, links=no), officially the Republic of the Philippines ( fil, Republika ng Pilipinas, links=no), * bik, Republika kan Filipinas * ceb, Republika sa Pilipinas * cbk, República de Filipinas * hil, Republ ...

beyond were one connected island. If verified, therefore, the Callao Man would have needed to have crossed open sea to reach the islands.

References

* ''Philippine Islands Sailing Directions'', third edition of the bulletin prepared in the office of the U.S. Coast and Geodetic Survey at

Manila Manila ( , ; fil, Maynila, ), officially the City of Manila ( fil, Lungsod ng Maynila, ), is the capital of the Philippines, and its second-most populous city. It is highly urbanized and, as of 2019, was the world's most densely populate ...

by Harry L. Ford, nautical expert (Washington, DC: Bureau of Printing, 1906), p. 171 * Lambert Anthony B. Meñez, Cesar L. Villanoy and Laura T. David. "Movement of Water Across Passages Connecting Philippine Inland Sea Basins" (Marine Science Institute, University of the Philippines, November 6, 2006)

External links

Map of Sibutu Passage (channel), Philippines
Encarta - MSN
Malaysia Map - Malaysia Satellite Image
- Geology.com Straits of the Philippines Straits of Malaysia Malaysia–Philippines border International straits {{Philippines-geo-stub