日本人群的源流一直是东亚地区人类学、考古学和遗传学研究的热点之一。1991年，埴原和郎（Hanihara Kazuro）提出了著名的“二重构造理论”（dual structure model）来解释日本人群的历史。该模型认为，来自东南亚地区旧石器时代晚期人群首先移居到日本列岛，创造了日本新石器文化——绳文文化（Jomon Culture），生产方式以狩猎采集为主；随着源自东北亚地区的第二批移民的到来，日本进入到以弥生文化（Yayoi Culture）为代表的铜石并用时代，生产方式转为农业栽培；这两批移民的经过相互混合，逐渐形成了今天的日本人群。然而，关于绳文文化是如何向弥生文化转变的问题却依旧备受争议。
在中国科学院昆明动物研究所张亚平院士的指导下，博士研究生彭旻晟尝试着从人类遗传学的角度来探讨这个问题。通过对已发表的952条日本人群的线粒体DNA（mtDNA）基因组进行分析，研究人员重建了日本人群的群体动态历史。结果显示，源自距今约5千年前的群体快速增长事件对现今日本人群的母系遗传库的形成起到了重要的作用。该时期大约对应于日本绳文时代中期，考古学证据表明当时的生产技术有了一定的进步，先民甚至开始驯化一些植物（例如稗子和葫芦），因此人口经历也了显著的增长。
有意思的是，这次群体快速增长一直持续至今，表明绳文文化向弥生文化的转变是一个“平顺”的过程，即不同时代的人口增长的态势是相互衔接的。这提示出，由于具备了相关的一些农业生产经验，绳文先民能够很快掌握随后由弥生时代移民传入的、更为先进的农业生产方式（例如水稻的水田栽培），继而在随后的弥生时代依旧保持人口的快速增长。
该研究发表在国际开源刊物《公共科学图书馆—综合》（PLoS ONE）上。（生物谷Bioon.com）
生物谷推荐原文出处：
PLoS ONE doi:10.1371/journal.pone.0021509
Inferring the Population Expansions in Peopling of Japan
Min-Sheng Peng, Ya-Ping Zhang
Background
Extensive studies in different fields have been performed to reconstruct the prehistory of populations in the Japanese archipelago. Estimates the ancestral population dynamics based on Japanese molecular sequences can extend our understanding about the colonization of Japan and the ethnogenesis of modern Japanese.
Methodology/Principal Findings
We applied Bayesian skyline plot (BSP) with a dataset based on 952 Japanese mitochondrial DNA (mtDNA) genomes to depict the female effective population size (Nef) through time for the total Japanese and each of the major mtDNA haplogroups in Japanese. Our results revealed a rapid Nef growth since ~5 thousand years ago had left ~72% Japanese mtDNA lineages with a salient signature. The BSP for the major mtDNA haplogroups indicated some different demographic history.
Conclusions/Significance
The results suggested that the rapid population expansion acted as a major force in shaping current maternal pool of Japanese. It supported a model for population dynamics in Japan in which the prehistoric population growth initiated in the Middle Jomon Period experienced a smooth and swift transition from Jomon to Yayoi, and then continued through the Yayoi Period. The confounding demographic backgrounds of different mtDNA haplogroups could also have some implications for some related studies in future.
