青藏高原牦牛驯化的考古学与遗传学研究进展及展望

Review and prospect of archaeological and genetic research on yak domestication on the Tibetan Plateau

家牦牛在史前人类定居青藏高原的过程中起到了巨大作用,但牦牛的驯化过程仍存在诸多未解决的科学问题.本文梳理了牦牛驯化的考古学和遗传学研究进展,展望了开展牦牛驯化与人类定居青藏高原过程研究的未来方向.家牦牛最早的考古学证据来自距今3750年前的青藏高原南部拉萨河谷,但现代遗传学研究显示,牦牛的驯化可追溯至全新世中期,驯化地点最有可能位于西藏东南部的昌都地区,其种群数量增长与人类大规模长年定居青藏高原高海拔地区的历史高度相关,且黄牛的基因渗入对牦牛的驯化过程产生了深刻影响.基于现有研究进展,本文建议:(1)针对青藏高原考古遗址开展系统性的动物考古学研究;(2)应用ZooMS和古DNA技术筛选和鉴定牦牛骨骼遗存,结合古环境DNA进行遗传学研究,追溯牦牛驯化的时间和地点;(3)开展野牦牛与黄牛的杂交驯化模式研究,理解牦牛驯化及其扩散对史前人类在青藏高原生存和发展的促进作用.

The domestic yak is a key animal species that facilitated prehistoric human exploring and settling on the Tibetan Plateau,particularly for permanent establishment in the high-altitude areas.It is hence well known as the"boat of the plateau"and"omnipotent livestock.As the most important livestock on the Tibetan Plateau,domestic yak has provided the herdsmen with meat,milk,transport power,fur,fuel and other necessary resources for production and life.However,limited by archaeological materials and disciplinary developments,the domestication process of yak is still not clear.Here we give an overview on the current status of yak domestication and how it is associated with human settlement on the Tibetan Plateau,from a multidisciplinary perspective mainly involving archaeological and genetic evidence,and also discuss into the possible directions for further studies concerning this issue.At present,the skeletal remains of yak unearthed from archaeological sites on the Tibetan Plateau are very limited.There are only 10 archaeological sites on the Tibetan Plateau where yak remains have been unearthed,among which the domestic yak remains unearthed from the Qugong site are the earliest and the most abundant.Available archaeological studies suggest that yak domestication occurred no earlier than 3750 years ago,and the domestication center might have been located in the Lhasa River valley,southern Tibetan Plateau.However,based on genetic analysis of mitochondrial and nuclear genomes of modern yak,its domestication can be traced back to the middle Holocene,earlier than the time indicated by archaeological evidence,and the inferred domestication center is in Changdu,southeastern Tibetan Plateau.The population size of yak is ciosely related to the human expansion and settlement on the Tibetan Plateau.Agriculture facilitated permanent human occupation of the high-altitude Tibetan Plateau about 3600 years ago,and a six-fold increase in population size of the domestic yak occurred during the same period.The introgression of cattle genes has a profound impact on the domestication process of yak and is an important source for the genetic diversity of yak.At the same time,the introgression of yak genes related to hypoxic adaptation promoted the adaptation of cattle to extreme environment of the Tibetan Plateau.Although ancient DNA is an ideal link between archaeology and genetics,and has been widely used in many species as a powerful means to study animal domestication,no ancient DNA study on yak has been published.Overali,it is still debatable about the timing,region,and process of yak domestication on the Tibetan Plateau,and there are obvious differences in the results of archaeological and genetic studies,mainly due to the lack of systematic zooarchaeological and ancient DNA study of high-altitude archaeological sites on the Tibetan Plateau.The formation and development of nomadic economy,the permanent settlement and the evolution of human livelihood patterns on the Tibetan Plateau have not been well answered.For future studies,the early hybridization between yak and cattle after cattle were introduced to the Tibetan Plateau will likely enable us to better understand the domestication process of yak and the promoting effect of yak domestication on the survival and establishment of prehistoric human on the Tibetan Plateau.More archaeological investigations,excavations,and zooarchaeological studies involving ZooMS and ancient DNA(both on fossil remains and sediments)studies on the Tibetan Plateau are required before we come to a stage for thoroughly addressing the detailed domestication process of yak.