Introduction
As the earliest species domesticated by humans, the domestic dog is the only animal to have been domesticated in the Pleistocene period,and both its domestication and dispersal have been closely linked to humans (Larson et al., 2012; Perri, 2016; Clutton-Brock, 2016; Janssens et al., 2018). The origin of the domestic dog remains a subject of controversy within the academic community, despite the general consensus that it likely emerged from one or more extinct wolf packs (Freedman et al., 2014; Skoglund et al., 2015; Frantz et al., 2016; Bergstrom ¨ et al.,2020). However, the precise geographic range and temporal stages of domestication continue to be subjects of ongoing debate (Savolainen et al., 2002; Verginelli et al., 2005; Pang et al., 2009; Gray et al., 2010; vonHoldt et al., 2010; Thalmann et al., 2013; Shannon et al., 2015; Perri et al., 2021; da Silva Coelho et al., 2021). This is attributed, in part, to the challenges in distinguishing morphologically between early domestic dog remains and grey wolves, as well as the scarcity of genomic data pertaining to ancient domestic dogs. In a recent study, it was suggested that domestic dogs may have undergone domestication either in eastern and western Eurasia or independently in eastern Eurasia before spreading westwards (Bergstrom ¨ et al., 2022). The data derived from the mitochondrial genomes of ancient domestic dogs in Northeast China, a region that serves as a vital link between the expansive Eurasian steppe and northern China, and holds significance in studying cultural exchange between the Eurasian steppe, northern China, and the Central Plains, will undoubtedly contribute crucial evidence to resolving this matter.
Current studies have demonstrated that domestic dogs can be categorized into four primary haplotypes, A, B, C, and D, the majority owhich fall under haplotype A (Savolainen et al., 2002; Perri et al., 2021;Duleba et al., 2015). Haplotype C is the most common haplotype among ancient European dogs and is considered to be the first haplotype to appear in Europe before the Neolithic period (Ollivier et al., 2018). For haplotype B, studies indicate that it exhibits characteristics associated with the Mediterranean region (Yankova et al., 2019). In previous studies on ancient Chinese domestic dogs, it was discovered that the overwhelming majority of dogs in ancient China belonged to haplotype A2 (Zhang et al., 2020, 2024; Wang et al., 2024).
