Homo luzonensis, also called Callao Man and known locally as "Ubag" after a mythical caveman, was an extinct species of early human from the Late Pleistocene period in Luzon, the Philippines. Fossil remains, including teeth and finger or toe bones, were found only in Callao Cave in the northern part of the island and date back to before 50,000 years ago. Scientists first thought these remains belonged to modern humans in 2010, but in 2019, after finding more fossils, they were classified as a new species. This classification was based on a mix of traits similar to modern humans, Australopithecus, and early Homo. In 2023, a study showed the fossils were about 134,000 years old, with a possible range of 14,000 years more or less, much older than previously believed.
The ancestors of Homo luzonensis, possibly Asian Homo erectus or an earlier Homo species, would have needed to cross the sea for at least several miles to reach the island. Evidence of early human presence on Luzon dates back as far as 771,000 to 631,000 years ago. People living in the cave brought in mainly Philippine deer carcasses and used tools to cut up meat.
Taxonomy
In 2007, zooarchaeologist Philip Piper found the first bone while examining animal bones collected during an archaeological dig led by Filipino archaeologist Armand Mijares in Callao Cave, Northern Luzon, Philippines. In 2010, Mijares and French bioanthropologist Florent Détroit, along with a team of international and local Philippine archaeologists, determined that the bones belonged to modern humans. After discovering 12 additional specimens and noting the presence of both modern human-like and primitive Australopithecus-like features, the researchers reclassified the remains (and other hominin findings from the cave) as a new species, Homo luzonensis. The species name comes from the island of Luzon.
The holotype, CCH6, includes the upper right premolars and molars. The paratypes are: CCH1, a right third metatarsal bone of 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 represents a juvenile femoral shaft. These remains are from at least three individuals. The specimens are stored at the National Museum of the Philippines in Manila.
The exact taxonomic classification of H. luzonensis is unknown. Like other tropical hominins, DNA extraction from the bones was not successful. It is possible that H. luzonensis descended from an early H. erectus population that migrated across Southeast Asia, similar to the hypothesis for H. floresiensis from Flores, Indonesia. Alternatively, H. luzonensis and H. floresiensis may have originated from a different Homo species that existed before H. erectus. The bones are dated to be older than 50,000 years, and evidence suggests hominin activity on the island as early as 771,000–631,000 years ago.
Anatomy
Homo luzonensis, like other animals found only on Luzon and Homo floresiensis, may have become smaller in size due to a process called insular dwarfism. However, more complete remains are needed to confirm this. Similar to Homo floresiensis, Homo luzonensis has features that are more like those of Australopithecus and early Homo than modern humans or more recent Homo.
The teeth of Homo luzonensis are small and shorter from front to back. Their molars are smaller than those of Homo floresiensis. Like other recent Homo and modern humans, the molars become smaller toward the back of the mouth, and the area where enamel meets dentin lacks clear wavy patterns. This area 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, the postcanine teeth of Homo luzonensis differ greatly from those of Paranthropus in size and shape. The premolars of Homo luzonensis share many features with those of Australopithecus, Paranthropus, and early Homo.
The finger bones of Homo luzonensis are long, narrow, and curved, a trait seen in Australopithecus, Homo floresiensis, and sometimes modern humans. These bones are flattened from the palm to the back of the hand and have well-developed areas where muscles attach, features also found in Australopithecus and early Homo habilis. A unique feature of Homo luzonensis is a strong, angled structure near the knuckle that points toward the wrist. The foot bones of Homo luzonensis are uniquely shaped compared to other Homo species and are different from those of Australopithecus africanus and Australopithecus afarensis. While Australopithecus limbs are often linked to walking upright and climbing trees, the incomplete remains of Homo luzonensis make it difficult to determine their movement patterns.
Because the remains are incomplete, it is hard to estimate the actual size of this species. However, they may have been similar in height to modern-day Philippine Negritos, who average about 151 cm (4 feet 11 inches) for males and 142 cm (4 feet 8 inches) for females.
Culture
Because Luzon has always been an island during the Quaternary period, the ancestors of H. luzonensis would have had to cross a large body of water over the Huxley Line.
About 90% of the bone pieces found in Callao Cave belong to the Philippine deer, which suggests that deer bodies were sometimes brought into the cave. Except for Palawan, where tigers lived, there is no evidence that large meat-eating animals lived in the Philippines during the Pleistocene. This indicates that humans were responsible for these remains. Other animals found there included the Philippine warty pig and an extinct type of bovid. A deer bone shows cut marks, and the lack of tools in the cave might be because humans used organic materials for tools instead of stone or because they processed meat outside the cave.
The Rizal Archaeological Site, located in Rizal, Kalinga, Philippines, has been studied by archaeologists since the 1950s. At this site, an almost complete skeleton of a rhino (Nesorhinus philippinensis, now extinct) was found, which had been butchered by early humans about 709,000 years ago. Alongside the rhino skeleton, six stone cores, forty-nine stone flakes, and two hammerstones were discovered. Some of the stone tools resemble those made from chert at the Arubo 1 site in central Luzon during the Lower Paleolithic period. Other remains found there included Stegodon, a type of elephant relative, the Philippine deer, freshwater turtles, and monitor lizards.