多國(guó)科學(xué)家合作研究發(fā)現(xiàn)，新的遺傳學(xué)證據(jù)顯示最早的美洲人分兩批移民到達(dá)美洲,。
參與該研究的有意大利,、美國(guó)、西班牙和中國(guó)的科研工作者,，中方參與研究的是來(lái)自云南大學(xué)和中科院昆明動(dòng)物研究所的孔慶鵬博士,。孔慶鵬于1999年9月自蘭州大學(xué)考入中科院昆明動(dòng)物研究所所攻讀碩士學(xué)位,， 2001年轉(zhuǎn)為博士生,，師從張亞平院士。其博士學(xué)位論文《東亞人群線(xiàn)粒體DNA系統(tǒng)發(fā)育基因組學(xué)研究》被評(píng)為2007年全國(guó)優(yōu)秀博士學(xué)位論文,。
在大約1.5萬(wàn)年到1.7萬(wàn)年前的末次盛冰期結(jié)束之后,，一組移民從白令地區(qū)進(jìn)入了北美，沿著沒(méi)有結(jié)冰的太平洋沿岸前進(jìn),，而另一組移民橫跨了兩個(gè)冰原之間的開(kāi)放的陸地走廊,，直接到達(dá)了落基山東部地區(qū)。（白令地區(qū)是在上一個(gè)冰期連接著東北西伯利亞和阿拉斯加的陸地,。）這組科學(xué)家說(shuō),，這些最早的美洲人后來(lái)形成了北美洲、中美洲和南美洲的幾乎所有的現(xiàn)代美洲原住民群體,，除了北美洲北部的納得內(nèi)以及愛(ài)斯基摩-阿留申群體這些重要的例外,。
“近來(lái)基于考古學(xué)證據(jù)和環(huán)境記錄的數(shù)據(jù)提示人類(lèi)最早在1.5萬(wàn)年前從白令地區(qū)進(jìn)入了美洲，而這種分散發(fā)生在解凍的太平洋沿海一帶，”意大利帕維亞大學(xué)的Antonio Torroni說(shuō),。“我們的研究如今揭示出了另一個(gè)新的可能性：在1.5萬(wàn)年前到1.7萬(wàn)年前來(lái)自白令地區(qū)的兩個(gè)幾乎相伴的移民路徑導(dǎo)致了古印第安人——最早的美洲人——的散布,。”
他說(shuō)，古印第安人這樣的雙重起源對(duì)于涉及美洲原住民研究的所有學(xué)科都有重大意義,。例如,，這意味著并沒(méi)有令人信服的理由去假定首批移民攜帶著單一的語(yǔ)系。
Torroni解釋說(shuō),，當(dāng)哥倫布于1492年到達(dá)美洲的時(shí)候,，美洲原住民生活的區(qū)域從白令海峽一直延伸到火地島。這些原住群體的語(yǔ)言和文化多樣性極大,，這已經(jīng)進(jìn)一步刺激了專(zhuān)家就他們的相互關(guān)系和起源問(wèn)題進(jìn)行的廣泛辯論,。
近來(lái)，分子遺傳學(xué)再加上考古學(xué)和語(yǔ)言學(xué)已經(jīng)開(kāi)始提供一些見(jiàn)解,。在這項(xiàng)新的研究中,，Torroni研究組的Ugo Perego 和Alessandro Achilli分析了來(lái)自?xún)蓚€(gè)罕見(jiàn)的單倍群的線(xiàn)粒體DNA，這意味著這些線(xiàn)粒體DNA有共同的母系祖先,。線(xiàn)粒體是擁有自己的DNA的細(xì)胞器,，它們可以讓科學(xué)家追蹤祖先和移民，因?yàn)樗鼈兪怯赡赣H直接傳給子女的,。
他們的結(jié)果顯示,，被稱(chēng)為D4h3的單倍群從白令地區(qū)開(kāi)始沿著太平洋沿海路徑在美洲傳播，迅速到達(dá)了火地島,。另有一個(gè)被稱(chēng)為X2a的單倍群在大約相同的時(shí)間里通過(guò)勞倫泰冰原和科迪勒拉冰原之間無(wú)冰的走廊傳播,，并僅限于在北美洲,。
“最早的美洲人的雙重起源從遺傳學(xué)角度看來(lái)是一個(gè)引人注目的新發(fā)現(xiàn),，它讓一個(gè)假說(shuō)變得看上去有道理，即在一個(gè)很短的時(shí)期里,，在動(dòng)態(tài)變化的白令地區(qū)可能存在進(jìn)入美洲的多個(gè)入口,，”這組科學(xué)家得出結(jié)論說(shuō)。（生物谷Bioon.com）
生物谷推薦原始出處：
Current Biology, Volume 19, Issue 1, 1-8, 13 January 2009 doi:10.1016/j.cub.2008.11.058
Distinctive Paleo-Indian Migration Routes from Beringia Marked by Two Rare mtDNA Haplogroups
Ugo A. Perego1,2,9,Alessandro Achilli1,3,9,Norman Angerhofer2,Matteo Accetturo1,Maria Pala1,Anna Olivieri1,Baharak Hooshiar Kashani1,Kathleen H. Ritchie2,Rosaria Scozzari4,Qing-Peng Kong5,6,Natalie M. Myres2,Antonio Salas7,Ornella Semino1,Hans-Jürgen Bandelt8,Scott R. Woodward2andAntonio Torroni1,,
1 Dipartimento di Genetica e Microbiologia, Università di Pavia, 27100 Pavia, Italy
2 Sorenson Molecular Genealogy Foundation, Salt Lake City, UT 84115, USA
3 Dipartimento di Biologia Cellulare e Ambientale, Università di Perugia, 27100 Perugia, Italy
4 Dipartimento di Genetica e Biologia Molecolare, Università La Sapienza, 00185 Rome, Italy
5 State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, 650223 Kunming, Yunnan, China
6 Laboratory for Conservation and Utilization of Bio-resource, Yunnan University, 650223 Kunming, Yunnan, China
7 Unidade de Xenética, Instituto de Medicina Legal, Facultad de Medicina, Universidad de Santiago de Compostela, 15782 Santiago de Compostela, Galicia, Spain
8 Department of Mathematics, University of Hamburg, 20146 Hamburg, Germany
9 These authors contributed equally to this work
It is widely accepted that the ancestors of Native Americans arrived in the New World via Beringia approximately 10 to 30 thousand years ago (kya). However, the arrival time(s), number of expansion events, and migration routes into the Western Hemisphere remain controversial because linguistic, archaeological, and genetic evidence have not yet provided coherent answers. Notably, most of the genetic evidence has been acquired from the analysis of the common pan-American mitochondrial DNA (mtDNA) haplogroups. In this study, we have instead identified and analyzed mtDNAs belonging to two rare Native American haplogroups named D4h3 and X2a.Phylogeographic analyses at the highest level of molecular resolution (69 entire mitochondrial genomes) reveal that two almost concomitant paths of migration from Beringia led to the Paleo-Indian dispersal approximately 1517 kya. Haplogroup D4h3 spread into the Americas along the Pacific coast, whereas X2a entered through the ice-free corridor between the Laurentide and Cordilleran ice sheets. The examination of an additional 276 entire mtDNA sequences provides similar entry times for all common Native American haplogroups, thus indicating at least a dual origin for Paleo-Indians.A dual origin for the first Americans is a striking novelty from the genetic point of view, and it makes plausible a scenario positing that within a rather short period of time, there may have been several entries into the Americas from a dynamically changing Beringian source. Moreover, this implies that most probably more than one language family was carried along with the Paleo-Indians.
