The paleoecology of Pleistocene birds from Middle Bed II, at Olduvai Gorge, Tanzania, and the environmental context of the Oldowan-Acheulean transition

Abstract

Fossil bird data (community composition and taphonomic profiles) are used here to infer the environmental context of the Oldowan-Acheulean transitional period at Olduvai Gorge, Tanzania. This is the first comprehensive report on the Middle Bed II avifauna and includes fossils excavated by the Olduvai Geochronology and Archaeology Project (OGAP) and recently rediscovered fossils collected by Mary Leakey. Crane, ibis, darter, owl, raptor, crow, and vulture are reported from Bed II for the first time. The presence of these taxa, absent earlier in this Bed, point to a general opening and drying of the landscape with grassland and open woodland expansion. Taxa associated with dense, emergent wetland vegetation, such as dabbling ducks and rails, are uncommon and less diverse than earlier in Bed II. This suggests more mature wetlands with clearer waters. Cormorants continue to be common, but are less diverse. Cormorants and other roosting taxa provide evidence of trees in the area. Compared to lowermost Bed II, the Middle to Upper Bed II landscape is interpreted here as more open and drier (but not necessarily more arid), with matured wetlands, scattered trees, and a greater expansion of grasslands.

Soil and Plant Phytoliths from the Acacia-Commiphora Mosaics at Oldupai Gorge (Tanzania)

“…Over the last few decades, different environmental proxies have been utilized in Africa to identify present-day ecosystems that could be used as referentials to frame the emergence of the genus Homo (Cerling et al, 1988;Barboni et al, 1999Barboni et al, , 2010Quinn et al, 2007;Albert and Marean, 2012;Barboni 2014;Esteban et al, 2017;Novello et al, 2018;Prassack et al, 2018). One of these analogs is the Acacia-Commiphora biome, where we studied a phytolith reference collection of characteristic plants that aided in the taxonomic identification of phytoliths from the underlying soils.…”

“…In East Africa, the transition to arid-adapted woodlands and grasslands over the last two million years has been documented in pedogenic carbonates (Cerling et al, 1988;Levin et al, 2004Levin et al, , 2011Quinn et al, 2007), mammal, bird, and fish fossils (Bibi and Kiessling, 2015;Bibi et al, 2018;Prassack et al, 2018), micro-and macrobotanical remains like pollen, phytoliths, and wood (Bonnefille, 1982(Bonnefille, , 1995Barboni et al, 1999), and stable isotopes of hydrogen and carbon from leaf wax lipid biomarkers (Magill et al, 2013a, b;Uno et al, 2016;Lupien et al, 2018).…”

“…Multiple proxies indicate that during the last two million years the East African climate changed, triggering a shift in its plant landscape from forested ecosystems to open woodland/grassland mosaics. These proxies include paleosol carbonates (Cerling et al, 1988;Levin et al, 2004;Quinn et al, 2007;Levin et al, 2011), vertebrates (Bibi and Kiessling, 2015;Bibi et al, 2018;Prassack et al, 2018), palaeobotanical remains (Bonnefille, 1984(Bonnefille, , 1995, and stable isotopes (Magill et al, 2013a, b;Uno et al, 2016;Lupien et al, 2018). This environmental transformation led to the widespread occurrence of a plant landscape characterized by Acacia-Commiphora woodland (White, 1983), and corresponds with key changes in hominin evolution and ecology (e.g.…”

Soil and plant phytoliths from theAcacia-Commiphoramosaics at Oldupai Gorge (Tanzania)

“…In East Africa, the transition to arid-adapted woodlands and grasslands over the last two million years has been documented in pedogenic carbonates (Cerling, Bowman & O’Neil, 1988; Levin et al, 2004; Levin et al, 2011; Quinn et al, 2007), mammal, bird, and fish fossils (Bibi & Kiessling, 2015; Bibi et al, 2018; Prassack et al, 2018), micro- and macrobotanical remains like pollen, phytoliths, and wood (Bonnefille, 1982; Bonnefille, 1995; Barboni et al, 1999), and stable isotopes of hydrogen and carbon from leaf wax lipid biomarkers (Magill, Ashley & Freeman, 2013a; Magill, Ashley & Freeman, 2013b; Uno, Polissar & Jackson, 2016; Lupien et al, 2018).…”

“…Multiple proxies indicate that during the last two million years the East African climate changed, triggering a shift in its plant landscape from forested ecosystems to open woodland/grassland mosaics. These proxies include paleosol carbonates (Cerling, Bowman & O’Neil, 1988; Levin et al, 2004; Quinn et al, 2007; Levin et al, 2011), vertebrates (Bibi & Kiessling, 2015; Bibi et al, 2018; Prassack et al, 2018), palaeobotanical remains (Bonnefille, 1984; Bonnefille, 1995), and stable isotopes (Magill, Ashley & Freeman, 2013a; Magill, Ashley & Freeman, 2013b; Uno, Polissar & Jackson, 2016; Lupien et al, 2018). This environmental transformation led to the widespread occurrence of a plant landscape characterized by Acacia-Commiphora woodland (White, 1983), and corresponds with key changes in hominin evolution and ecology (e.g., Ravelo et al, 2004; Lepre et al, 2011; Beyene et al, 2013).…”