Homo luzonensis – another member of the human family found in southeast Asia.

Callao Cave lies within what was initially, the Callao Cave National Park. It was first set up during the American colonial period of the Philippines (1898-1946). The then, American Governor-General Theodore Roosevelt, Jr., (son of the American president), created the Philippines, National Park system with the passing of Act No. 3195. Callao Cave became one of the earliest national parks of the country when it was established on July 16, 1935. The park has been enlarged several times since, and now forms part of the Peñablanca Protected Landscape and Seascape.

Prior to the archaeological interest of the cave being established, it was a show cave with 11 chambers. The cathedral-like first chamber is the largest room with a width of about 50 m (160 ft) and a height of 36 m (118 ft). This chamber has been turned into a chapel by the local people with the alter a natural rock formation lit by a stream of light from an opening in the roof.

Callao cave from Tayag (2019)

Excavations in 2007 by Armand Salvador Mijares discovered the first human fossil: a metatarsal, tentatively assigned, at the time to Homo sapiens. Excavations continued and further fossils were uncovered.

Based on the metatarsal found in 2007 and other more recently discovered bones a new species of human was announced in April 2019, by Détroit et al. (2019).

Named Homo luzonensis for the island of its discovery in the Philippines, the bones have been dated to 67,000BP by the U/Th method. The fossil collection consists of an additional 12 bones and teeth. From the paper: “Continued excavations in Callao Cave that originally yielded the hominin third metatarsal (which we here call CCH1 for ‘Callao Cave Hominin 1’) have produced another twelve hominin elements from the same stratigraphic layer (layer 14): seven postcanine maxillary teeth (CCH6-a to CCH6-e, CCH8, CCH9); two manual phalanges (CCH2 and CCH5); two pedal phalanges (CCH3 and CCH4) and a femoral shaft (CCH7). CCH1 and CCH6-a are directly dated by U-series analysis to minimum ages of 67 thousand years (kyr) and 50 kyr, respectively. Crown morphology, grade of occlusal wear and exact correspondences of interproximal contact facets demonstrate that five of the upper right teeth belonged to a single individual (CCH6-a to CCH6-e).

The molars and pre-molars of Homo luzonensis from Margaritoff (2019). These are the fossils named as CCH6a-e.

These teeth along with two others (a L P3/4 and an additional R M3), do not match those of any known hominin species. Put simply: their varied morphology and small sizes do not match any human ancestors. As Détroit et al (2019) point out: “the overall pattern of morphology seen in the dental remains of H. luzonensis is easily distinguishable from all previously described hominin species.”

Pruitt (2019) on the proximal phalanx recovered: “The foot bones identified as Homo luzonensis also stand out for their combination of primitive and developed features, which indicates members of the species might have had a distinctive way of walking. The proximal phalanx (which forms the base of the toe) is curved, with highly developed insertions for the muscles involved in the flexion of the foot.” She also interviewed Détroit: “These characteristics do not exist in Homo sapiens,” he said. In fact, the foot bones found in Callao Cave are more similar, to Australopithecus, which was known to live only in Africa some 2-3 million years ago. This suggests Homo luzonensis might (like Australopithecus) have had the ability to easily climb trees as well as walk upright on two legs, though it’s not clear whether they did so.

Proximal phalanx excavated from Callao cave, from Pruitt (2019). Original caption reads: “A proximal foot phalanx of Homo luzonensis, showing the longitudinal curvature of the bone.”

The remainder of the pedal and manual phalanxes also showed affinities to Australopithecines.

The final fossil found was a femoral shaft. Again from Détroit: “The referred specimen, CCH7, is a partial left femur from which both the proximal and distal ends are missing. Transverse slices of micro-computed tomography (micro-CT) scans show a high density of Haversian canals in the cortical bone that is characteristic of a growing juvenile individual.“ Due to its incomplete nature it was of little diagnostic value, except to show that the species was probably of short stature.

Finally Détroit et al. conclude: “The presence of two right upper third molars (M3; CCH6-a and CCH9) and a juvenile femoral shaft (CCH7) indicates that at least three individuals are represented. On the basis of the unique mosaic of primitive (that is, Australopithecus-like) and derived (that is, H. sapiens-like) morphological features observed on these specimens, we assign them to a new species, H. luzonensis.”

Whilst these remains put archaic humans, possibly related to Australopithecines, in Luzon as recently as 50,000 years ago when they arrived is an open question. However, other definite, evidence of occupation of the island has been published recently.

Ingicco et al. (2018) excavated a site in the Cagayan valley of northern Luzon, only 30km from Calao Cave. This site (Kalinga) has yielded 57 stone tools and remains of megafauna (Rhinoceros philippinensis): an almost-complete disarticulated skeleton, which shows clear signs of butchery. Other fossil faunal remains found are attributed to stegodon, Philippine brown deer, freshwater turtle and monitor lizard. All finds originate from a clay-rich bone bed that was dated to between 777 and 631 thousand years ago using electron-spin resonance methods that were applied to tooth enamel and fluvial quartz.

Regionally both east and west of the Wallace line there are a number, of equally old or slightly younger finds. The map below shows some of the most important sites:

Important south east Asian regional hominin sites adapted from Soares et al. (2008). Dark grey: current coastline; light grey: sea level at LGM -120m, here assumed to be similar to low stands during previous glaciations. It is noteworthy that all sites occupied between 700,000 and 50,000BP were at one time or another, within easy reach of Sundaland.

These include:

The original Homo erectus material from Trinil and further discoveries made on Java. Dating on these fossils is still contentious, with dates ranging from as recent as ca. 70,000BP to as old as ca. 550,000BP.

The 110,000-200,000 year old stone tools from Sulawesi I covered in an earlier post (see here).

The Homo floresiensis material from Liang Bua Cave on Nusa Tunggara East (“Flores”). This is another small bodied, possibly Australopithecine, related hominin which survived to approximately 50,000BP.

From the same island is the Mata Menge jawbone, predating Homo floresiensis by a full 650,000 years, yet still hypothesised to be the ‘Hobbit’s’ ancestor. Whilst the huge time span of these dates seems to make this hypothesis far-fetched a recent paper by Argue et al. (2017) based on morphometric comparisons has found that: “H. floresiensis is sister either to H. habilis alone or to a clade consisting of at least H. habilis, H. erectus, Homo ergaster, and H. sapiens. A close phylogenetic relationship between H. floresiensis and H. erectus or H. sapiens can be rejected; furthermore, most of the traits separating H. floresiensis from H. sapiens are not readily attributable to pathology (e.g., Down syndrome). The results suggest H. floresiensis is a long-surviving relict of an early (>1.75 Ma) hominin lineage and a hitherto unknown migration out of Africa, and not a recent derivative of either H. erectus or H. sapiens.”

Lastly there are the Acheulian stone tools from the Air Tawar in southern Sumatra excavated by a French team – see Forestier (2007). These are between 400,000 and 200,000 years old and are some of the largest bifaces found outside of Africa being over 30cm long.

Acheulian biface discovered at Air Tawar, southern Sumatra from Forestier (2007).

Whilst the original finding of Homo floresiensis seemed at the time of its discovery a one-off fluke survival, the further discoveries in south east Asia have begun to paint a picture of far greater Middle Pleistocene, hominin diversity in the region than previously suspected.

Indeed, if we consider the unexplained fossils from nearby mainland Asia, such as those of the Red Deer People, Maba, Dali and Jinniushan we can see that the history of human migration and evolution in the region is far more complex than previously believed.

Personally, I think that true version of the human story in south east Asia has yet to be even dreamed of by current scientists. If I have a Damascene moment and come up with something paradigm-shattering, I’ll let you know.

References

Argue, D., Groves, C.P., Lee, M.S. and Jungers, W.L., 2017. The affinities of Homo floresiensis based on phylogenetic analyses ofácranial, dental, and postcranial characters. Journal of Human Evolution, 107, pp.107-133.

Détroit, F., Mijares, A.S., Corny, J., Daver, G., Zanolli, C., Dizon, E., Robles, E., Grün, R. and Piper, P.J., 2019. A new species of Homo from the Late Pleistocene of the Philippines. Nature, 568(7751), p.181.

Ingicco, T., van den Bergh, G. D., Jago-On, C., Bahain, J., Chacón, M. G., Amano, N., Forestier, H., King, C., Manalo, K., Nomade, S., Pereira, A., Reyes, M. C., Semah, A., Shao, Q., Voinchet, P., Falgueres, C., Albers, P. C.H., Lising, M., Lyras, G., Yurnaldi, D., Rochette, P., Bautista, A. & de Vos, J. (2018). Earliest known hominin activity in the Philippines by 709 thousand years ago. Nature, 557 233-237.

Forestier, H., 2007. Les éclats du passé préhistorique de Sumatra: une très longue histoire des techniques. Archipel, 74(1), pp.15-44.

Margaritoff, M (2019) “Meet The Hobbit-Like Early Human Ancestor Known As Callao Man” from https://allthatsinteresting.com/callao-man-homo-luzonensis accessed 05.08.19

Pruitt, S. (2019) “Previously Unknown Human Species Discovered in the Philippines” A and E Television Networks at https://www.history.com/news/new-hominin-homo-luzonensis-discovery-philippines accessed 04.08.19

Soares, P., Trejaut, J.A., Loo, J.H., Hill, C., Mormina, M., Lee, C.L., Chen, Y.M., Hudjashov, G., Forster, P., Macaulay, V. and Bulbeck, D., 2008. Climate change and postglacial human dispersals in Southeast Asia. Molecular Biology and Evolution, 25(6), pp.1209-1218.

Tayag, Y. (2019). “A New Species of Ancient Human Was Discovered in a Cave in the Philippines” from Inverse at https://www.inverse.com/article/54763-new-species-of-human-is-called-homo-luzonensis accessed 05.08.19