Extended Data Fig. 1: Evolutionary and geomorphical history of region.

The landscape evolutionary stages that created the Solo River terraces. Drawn from refs. ^2,3 on a topographical map from the USGS EROS. a, More-than 500-ka drainage from the proto-Merapi and Lawu volcanic highlands formed a lake or lagoon from which the proto-Solo River drained to the south (blue arrow), close to the present-day Pacitan region, and another branch flowed to the north of Lawu. By at least 1.5 million years ago, the Southern Mountains to the south and the Kendeng anticlinorium to the north were slowly emerging, forming the Gunung Sewu, and the Kendeng Hills (previously the Randublantung marine embayment²), respectively. b, By about 500 ka, the seismically uplifted Southern Mountains had blocked the southern exit of the Solo River to the ocean, and the area was dominated by trunk streams of the Solo River. c, Between about 500 and 316 ka, the Solo River abandons its southern trunk stream and extends its northern branch, where it is diverted to the west and northeast and carves an initial crossing through the Kendeng Hills to form the Solo River gap, and drain into the ocean to the north of Surabaya. d, Between about 316 and 31 ka, the uplifting Kendeng anticlinorium and the drainage from the Madiun Basin energized the Solo River, causing incision and forming the Solo River sequence of terraces (white parallel lines). e, Present-day Solo Basin and known fossil sites on exposed terraces. f, A digital elevation model^31,32, comprising a satellite image overlying a topographical map of the section of the Solo River system from Kerek village in the south to Sunggun village in the north (USGS Landsat). g, The same digital elevation model, with the classification scheme for the Solo River terraces with the upper, middle, lower and lowermost terraces identified. This image includes the key terrace sites that are sampled in this study; Kerek (upper), Padasmalang (middle), Sembungan (lower), Nglebak (lowermost) and Menden (outside of the Kendeng Hills, but contemporaneous with the upper and middle terraces), and the key fossil site of Ngandong (lower). The white dashed line indicates the limits of the Kendeng Hills. The Menden terrace lies outside of this divide, as does the westward-bearing Solo River and the site of Trinil.