Climate amelioration, abrupt vegetation recovery, and the dispersal of Homo sapiens in Baikal Siberia

Abstract

The dispersal of Homo sapiens in Siberia and Mongolia occurred by 45 to 40 thousand years (ka) ago; however, the climatic and environmental context of this event remains poorly understood. We reconstruct a detailed vegetation history for the Last Glacial period based on pollen spectra from Lake Baikal. While herb and shrub taxa including Artemisia and Alnus dominated throughout most of this period, coniferous forests rapidly expanded during Dansgaard-Oeschger (D-O) events 14 (55 ka ago) and 12 to 10 (48 to 41 ka ago), with the latter presenting the strongest signal for coniferous forest expansion and Picea trees, indicating remarkably humid conditions. These abrupt forestation events are consistent with obliquity maxima, so that we interpret last glacial vegetation changes in southern Siberia as being driven by obliquity change. Likewise, we posit that major climate amelioration and pronounced forestation precipitated H. sapiens dispersal into Baikal Siberia 45 ka ago, as chronicled by the appearance of the Initial Upper Paleolithic.

Fig. 1.. The Baikal Siberia study area.

(A) Regional map of Lake Baikal and the Cisbaikal and Transbaikal regions; (B) area map showing locations of the core-drilling area and archaeological sites (shown in numbers) used in radiocarbon analysis; (C) close-up map of BDP-99 core-drilling site and other drilling sites (shown in letters) discussed in text; (a) BDP-99 (this study); (b) VER99G12 (35); (c) BDP-93-2 (21); (d) Lake Kotokel (22, 86); 1, Alekseevesk; 2, Arembovskii; 3, Arta-2; 4, Balyshevo-3; 5, Barun-Alan-1; 6, Bol’shoi Naryn-1 and 2; 7, Bol’shoi Zangisan; 8, Buret’; 9, Cheremushnik; 10, Chitkan; 11, Gerasimova-1; 12, Igeteiskii Log-1, 2, 3; 13, Kamenka; 14, Kandabaevo; 15, Khenger-Tin-3 and Khenger-Tin Skal’naia; 16, Khotyk-3; 17, Kiriushina; 18, Krasnyi Iar; 19, Kunalei; 20, Kurla-3; 21, Lagernaia; 22, Makarovo-3 and 4; 23, Mal’ta, Mal’ta Most-1, and Mal’ta Strelka; 24, Mamakan-1 and 2; 25, Mamony-2; 26, Masterov Kliuch’; 27, Nepa-1; 28, Novyi Angarskii Most; 29, Podzvonkaia; 30, Priiskovoe; 31, Sannyi Mys; 32, Sedova; 33, Shchapovo-1 and 2; 34, Shishkino-8; 35, Slavin Iar; 36, Sokhatino-4; 37, Studenoe-1 and 2; 38, Tolbaga; 39, Tuiana; 40, Ust’-Ëdarma-2; 41, Ust'-Kiakhta-16; 42, Ust’-Kova; 43, Ust’-Menza-2; 44, Ust’-Odinskii; 45, Utan; 46, Varvarina Gora; 47, Voennyi Gospital. The location of the Tolbor sites in Mongolia is also shown.

Fig. 2.. Lithology and age model of the BDP-99 core.

1, Diatom; 2, clay; 3, silt and sand; 4, missing core section; 5, age-control points from the diatom assemblage (72, 77); 6, peak-matching points of grain size fluctuations (78) and insolation curve at 65°N in June (79). BP, before present.

Fig. 3.. Selected pollen and spore diagrams for the BDP-99 core.

Exaggerated curves of pollen concentration show percentage data with 10× amplification (lithology: 1, diatom; 2, clay; 3, silt and sand; 4, missing core section). AP, arboreal pollen. The division of each marine isotope stage by the LR04 stack (24) is also shown.

Fig. 4.. A semilogarithmic graph of PAR of the BDP-99 core with the regression curve using the locally weighted least squares error method with 20%.

The LR04 stack of δ¹⁸O and division of each MIS (24) is also shown.

Fig. 5.. Chronological distributions of Paleolithic radiocarbon dates for entire Baikal region.

(A) By all radiocarbon dates; (B) by dated occupations per millennium; (C) by kernel density modeling of all radiocarbon dates.

Fig. 6.. Chronological distributions of Paleolithic radiocarbon dates for Cisbaikal region.

(A) By all radiocarbon dates; (B) Bby dated occupations per millennium; (C) Bby kernel density modeling of all radiocarbon dates.

Fig. 7.. Chronological distributions of Paleolithic radiocarbon dates for Transbaikal region.

(A) By all radiocarbon dates; (B) by dated occupations per millennium; (C) by kernel density modeling of all radiocarbon dates.

Fig. 8.. Comparison of pollen diagram from BDP-99 core and δ¹⁸O curve and orbital variations.

(A) North Greenland Ice Core Project (NGRIP) δ¹⁸O curve with the number of D-O events (27); (B) NAP percentage; (C) broad-leaved pollen percentage; (D) coniferous pollen percentage; (E) Picea percentage of BDP-99 core; (F) obliquity; (G) precession calculated by using the La2004 orbital solution (28). Gray bars indicate approximate positions in the pollen assemblage of BDP-99 core correlating the D-O events of NGRIP.

Fig. 9.. The hypothesized dispersal of Homo sapiens.

This dispersal is defined by initial Upper Paleolithic industries, originating from southwestern Asia and extending into Europe in the west and Siberia in the east.