Homo luzonensis, also called Callao Man and known as "Ubag" in local stories, was an ancient human species that lived during the Late Pleistocene on the island of Luzon in the Philippines. Fossils found at Callao Cave in northern Luzon include teeth and finger and toe bones. These remains are more than 50,000 years old. Scientists first thought these bones belonged to modern humans in 2010. However, in 2019, more fossils were discovered, and researchers classified them as a new species because they had features similar to modern humans, Australopithecus, and early Homo. A study in 2023 showed the fossils were about 134,000 years old, with a possible range of 14,000 years.
The ancestors of Homo luzonensis may have been Asian Homo erectus or an even earlier human species. These ancestors likely traveled across the sea to reach Luzon. Evidence shows humans lived on Luzon as early as 771,000 to 631,000 years ago. People in the cave brought Philippine deer carcasses inside and used tools to cut up the meat.
Taxonomy
In 2007, a scientist named Philip Piper found the first bone while examining animal bones collected from an archaeological site in Callao Cave, Northern Luzon, Philippines. This site was studied by Filipino archaeologist Armand Mijares. In 2010, Mijares and French scientist Florent Détroit, along with other archaeologists, determined that the bones belonged to modern humans. Later, after finding 12 more bones and noticing both human-like and older Australopithecus-like traits, the scientists reclassified the remains and other hominin fossils from the cave as a new species called Homo luzonensis. The name luzonensis comes from the island of Luzon.
The holotype, labeled CCH6, includes the upper right premolars and molars. The paratypes are: CCH1, a right third metatarsal bone from the foot; CCH2 and CCH5, two finger phalanges; CCH3 and CCH4, two foot phalanges; CCH4, a left premolar; and CCH9, a right third molar. CCH7 is a juvenile femoral shaft. These bones represent at least three individuals. They are stored at the National Museum of the Philippines in Manila.
The exact classification of Homo luzonensis is unknown. Scientists could not extract DNA from the bones, as is often the case with tropical hominins. It is possible that Homo luzonensis descended from an early group of Homo erectus that spread across Southeast Asia, similar to the hypothesis for Homo floresiensis found on Flores, Indonesia. Another possibility is that Homo luzonensis and Homo floresiensis originated from a different Homo species that existed before Homo erectus. The bones are dated to be older than 50,000 years, and evidence shows hominin activity on the island as early as 771,000 to 631,000 years ago.
Anatomy
Homo luzonensis, like other animals found only on Luzon and Homo floresiensis, may have become smaller due to a process called insular dwarfism. More complete remains are needed to confirm their size. Similar to H. floresiensis, H. luzonensis shares traits more closely with Australopithecus and early Homo than with modern humans or recent Homo species.
The teeth of H. luzonensis are small and shorter from front to back. Their molars are smaller than those of H. floresiensis. Like other recent Homo and modern humans, the molars become smaller toward the back of the mouth, and the enamel-dentine juncture lacks clear wavy patterns. This feature is most similar to that of Asian Homo erectus. The premolars are unusually large compared to the molars, with proportions more like those of Paranthropus than any other Homo. However, H. luzonensis postcanine teeth differ greatly from Paranthropus in size and shape. The premolars of H. luzonensis share traits with Australopithecus, Paranthropus, and early Homo.
The finger bones of H. luzonensis are long, narrow, and curved, a trait seen in Australopithecus, H. floresiensis, and sometimes modern humans. These bones are compressed from the palm to the back of the hand and have well-developed flexor sheath attachments, similar to Australopithecus and early Homo habilis. A unique feature of H. luzonensis is a strongly developed dorsal beak near the knuckle, angled toward the wrist rather than the finger. The foot bones of H. luzonensis are distinct among Homo and differ from those of Australopithecus species. Australopithecus limbs are often linked to bipedalism and possible tree-climbing behavior, but the incomplete remains of H. luzonensis make it hard to determine their locomotion.
Because the remains are incomplete, it is difficult to estimate the exact size of H. luzonensis. However, they may have been similar in size to modern-day Philippine Negritos, who average 151 cm (4 ft 11 in) for males and 142 cm (4 ft 8 in) for females.
Culture
Because Luzon has always been an island during the Quaternary period, the ancestors of Homo luzonensis would have needed to travel a long sea journey across the Huxley Line.
About 90% of the bone pieces found in Callao Cave belong to the Philippine deer. This suggests that deer remains were brought into the cave from time to time. Except for Palawan, where tigers lived, there is no evidence that large carnivores lived in the Philippines during the Pleistocene. This means the animal remains were likely left by humans. Other animals found in the cave include the Philippine warty pig and an extinct type of bovid. A deer tibia has cut marks, and the lack of tools in the cave may be because early humans used organic materials instead of stone for tools, or they processed meat outside the cave.
The Rizal Archaeological Site, located in Rizal, Kalinga, Philippines, was explored by archaeologists since the 1950s. It uncovered nearly a full skeleton of an extinct rhino (Nesorhinus philippinensis), which was cut up by early humans about 709,000 years ago. Along with the rhino bones, six lithic cores, forty-nine lithic flakes, and two hammerstones were found at the site. Some of the cores and raw materials resemble the chert tools from the Lower Paleolithic Arubo 1 site in central Luzon. Other remains found include the elephant-like animal Stegodon, the Philippine deer, freshwater turtles, and monitor lizards.