Exploring the Y Chromosomal Ancestry of Modern Panamanians

Geologically, Panama belongs to the Central American land-bridge between North and South America crossed by Homo sapiens >14 ka ago. Archaeologically, it belongs to a wider Isthmo-Colombian Area. Today, seven indigenous ethnic groups account for 12.3% of Panama’s population. Five speak Chibchan languages and are characterized by low genetic diversity and a high level of differentiation. In addition, no evidence of differential structuring between maternally and paternally inherited genes has been reported in isthmian Chibchan cultural groups. Recent data have shown that 83% of the Panamanian general population harbour mitochondrial DNAs (mtDNAs) of Native American ancestry. Considering differential male/female mortality at European contact and multiple degrees of geographical and genetic isolation over the subsequent five centuries, the Y-chromosome Native American component is expected to vary across different geographic regions and communities in Panama. To address this issue, we investigated Y-chromosome variation in 408 modern males from the nine provinces of Panama and one indigenous territory (the comarca of Kuna Yala). In contrast to mtDNA data, the Y-chromosome Native American component (haplogroup Q) exceeds 50% only in three populations facing the Caribbean Sea: the comarca of Kuna Yala and Bocas del Toro province where Chibchan languages are spoken by the majority, and the province of Colón where many Kuna and people of mixed indigenous-African-and-European descent live. Elsewhere the Old World component is dominant and mostly represented by western Eurasian haplogroups, which signal the strong male genetic impact of invaders. Sub-Saharan African input accounts for 5.9% of male haplotypes. This reflects the consequences of the colonial Atlantic slave trade and more recent influxes of West Indians of African heritage. Overall, our findings reveal a local evolution of the male Native American ancestral gene pool, and a strong but geographically differentiated unidirectional sex bias in the formation of local modern Panamanian populations.

从地质学角度而言，巴拿马属于连接南北美洲的中美洲陆桥，智人（Homo sapiens）于距今超过1.4万年前便在此迁徙通行。从考古学视角来看，它隶属于范围更广的地峡-哥伦比亚文化区（Isthmo-Colombian Area）。如今，7个原住民族群占巴拿马总人口的12.3%，其中5个族群使用奇布查语系（Chibchan languages）语言，其遗传多样性较低且群体分化程度较高。此外，目前尚无研究报道称，地峡地区的奇布查文化族群中，母系遗传基因与父系遗传基因之间存在结构性差异。近期研究数据显示，巴拿马普通人群中有83%的个体携带有美洲原住民祖先的线粒体DNA（mitochondrial DNAs, mtDNA）。考虑到欧洲殖民者抵达时出现的性别差异化死亡率，以及随后500年间不同程度的地理与遗传隔离现象，巴拿马不同地理区域和族群的Y染色体（Y-chromosome）美洲原住民成分理应存在差异。为解决这一问题，我们对来自巴拿马9个省份及1个原住民领地（库纳雅拉特区（comarca of Kuna Yala））的408名现代男性的Y染色体变异情况进行了分析。与线粒体DNA的研究结果不同，Y染色体美洲原住民成分（Q单倍群（haplogroup Q））仅在三个濒临加勒比海的群体中占比超过50%：分别是库纳雅拉特区、以奇布查语族为主要使用人群的博卡斯德尔托罗省，以及聚居着大量库纳人与原住民-非裔-欧裔混血人群的科隆省。在其余区域，旧大陆遗传成分占据主导地位，且多以西欧亚单倍群为主，这反映出外来入侵者对当地男性基因库的强烈影响。撒哈拉以南非洲血统的遗传成分占男性单倍型的5.9%，这与大西洋沿岸殖民奴隶贸易以及近代非裔西印度群岛移民的涌入密切相关。综上，本研究结果揭示了男性美洲原住民祖先基因库的本地演化过程，同时表明在现代巴拿马本地人群的形成过程中，存在强烈且具有地理分化特征的单向性别遗传偏向。