PEOPLING

Homo luzonensis, the Callao Cave Human

~67,000 years ago (debated)

Palaeolithic · Middle Stone Age · Last glacial

Callao Cave, in northern Luzon in the Philippines, yielded in 2007 a hominin third metatarsal, a bone of the foot, which direct uranium dating placed at a minimum of 66,700 ± 1,000 years and which was then the oldest human fossil known in the archipelago. Twelve further elements, belonging to at least three individuals, came from the same stratigraphic layer. Their describers reported in 2019 a combination of primitive and derived features unlike that found in any other member of the genus, including Homo floresiensis and Homo sapiens, and named a new species, Homo luzonensis. The foot bone is slender and falls within the size and shape ranges of small-bodied Homo sapiens, of Homo habilis and of Homo floresiensis, which is why its attribution to a species took a further nine years and twelve more bones.

Why it matters

Luzon is an isolated island: reaching it meant a crossing of open sea, and someone made one more than six hundred thousand years ago, since stone tools and a butchered rhinoceros at another site on the island lie in a bed dated between 777,000 and 631,000 years. The Callao fossils belong to a population distinct from Homo floresiensis on Flores and from Homo sapiens, east of the Wallace Line, the faunal boundary that separates Asian from Australasian animal life. Island Southeast Asia carried more than one kind of human, and was no empty corridor towards Australia.

Dating & uncertaintyDisputed

Every age proposed for these fossils is a minimum, since uranium series dating of bone measures the time since uranium entered it from the ground. The foot bone gave a minimum of 66,700 ± 1,000 years, and that figure has served as the age of the species. A systematic re-evaluation of the published uranium series data, in 2023, concluded that the younger values come from later uranium overprints and that the true minimum is 134,000 ± 14,000 years. The difference decides whether these individuals lived close to the arrival of Homo sapiens in the region or tens of millennia before it.

Sources

1. Détroit et al. (2019), Nature · A new species of Homo from the Late Pleistocene of the Philippinesdoi:10.1038/s41586-019-1067-9
2. Mijares et al. (2010), Journal of Human Evolution · New evidence for a 67,000-year-old human presence at Callao Cave, Luzon, Philippinesdoi:10.1016/j.jhevol.2010.04.008
3. Grün et al. (2023), Quaternary Science Reviews · Direct dating of human fossils and the ever-changing story of human evolutiondoi:10.1016/j.quascirev.2023.108379
4. Ingicco et al. (2018), Nature · Earliest known hominin activity in the Philippines by 709 thousand years agodoi:10.1038/s41586-018-0072-8

Our species’ history as one day

18:53:425 h 6 min before midnight

if the 315,000 years of Homo sapiens were compressed into a single day