Abstract
Peach (Prunus persica, Rosaceae) is an extremely popular tree fruit worldwide, with an annual production near 20 million tons. Peach is widely thought to have origins in China, but its evolutionary history is largely unknown. The oldest evidence for the peach has been Chinese archaeological records dating to 8000–7000 BP. Here, we report eight fossil peach endocarps from late Pliocene strata of Kunming City, Yunnan, southwestern China. The fossils are identical to modern peach endocarps, including size comparable to smaller modern varieties, a single seed, a deep dorsal groove, and presence of deep pits and furrows. These fossils show that China has been a critical region for peach evolution since long before human presence, much less agriculture. Peaches evolved their modern morphology under natural selection, presumably involving large, frugivorous mammals such as primates. Much later, peach size and variety increased through domestication and breeding.
Highlights
1 km Description—Stony endocarps (Fig. 2) elliptical, flattened in lateral view, base obtuse, apex apiculate, length 2.6–3.0 cm, width 1.8–2.3 cm, length:width ratio 1.3–1.6:1, thickness 0.8–1.2 cm
Subgenus Amygdalus is consistent with the fossils in having the largest endocarp size and because it is the only subgenus with species that have both furrows and pits on the endocarps (Figs 2 and 3a)
Many additional features of the fossils show their close affinity to the living peach, Prunus persica, as seen in our full character matrix for 36 modern Prunus species, plus the fossils, that shows identical scores for the fossils and modern peaches (Fig. 4; Supplementary Table 1)
Summary
(a) Geologic map, modified from Bureau of Geology and Mineral Resources of Yunnan Province, 199030 with the software Adobe Illustrator CS4. Description—Stony endocarps (Fig. 2) elliptical, flattened in lateral view (presumably compressed), base obtuse, apex apiculate, length 2.6–3.0 cm, width 1.8–2.3 cm, length:width ratio 1.3–1.6:1, thickness 0.8–1.2 cm. Endocarp exterior surface with both furrows and pits. Single deep groove of vascular bundle canal on dorsal side, extending from base to apex. Transverse furrows (Fig. 2a) one or two, following edges of both dorsal and ventral sides. Longitudinal furrows (Fig. 3a) seven to ten, radiating apically from the base over less than half the endocarp length. Deep pits (Fig. 2) mainly situated near the apex. Seed (Fig. 2f) single, flattened, elliptical, base round, apex acute, length ~1.9 cm, width ~1.0 cm, replaced by iron compounds
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