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本帖最后由 tosylate 于 2018-1-7 13:02 编辑

long-term Beringian standstill model, 所谓长期白令滞留模型, 有其合理性,在30kyBP的yana river 遗址, 虽然没有人骨,但有明确无误的人工制品,如果假设不是西伯利亚丹人的,那就是智人曾经在Beringia活动的证据,所以这个模型是认为现代人类在那个时候就到了极地地区,但之后的LGM使幸存者躲到Beringia南部一带来避难,那个地区在LGM不是那么寒冷,也没有冰川,类似现在北极圈的tundra植被, 可以维持一个小规模人群的存在。在LGM后冰川退缩,一旦向南的通道打开,就迁移到美洲大陆了。

在LGM期间是瓶颈效应,造成人群多样性大为减少,也可以解释为什么Native American的EA基因占优,但Y-DNA却是以ANE的Q为主。

但是,这个模型目前没有考古上的证据,目前,在原Beringia地区,在30kyBP之后人类遗址,就是14kyBP,之间没有可靠的人类活动的考古证据, 有个Bluefish Caves, 但看了看,实在不足为证,在大批的动物骨头里找到几个有划痕的,就以为是人类活动的证据了。

人类也完全可以在LGM后来到Beringia,比如18-13kyBP之间,那个”桥“的淹没是滞后的,直到11kyBP才完全淹没, 所以完全可能呆个短的时间(short term),等待南下的通道开通之后才南下,一般认为陆路通道开通是13-12kyBP, 沿海通道早一些,大概15-14kyBP就开通了。
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  • Ryan

迁移路线图
boergia.jpg
物格而后知至,知至而后意诚,意诚而后心正,心正而后身修,身修而后家齐,家齐而后国治,国治而后天下平...
文章摘要说结果与文献[9]的Beringian standstill model相符合。去看了一下,文献[9]发表于2007年,研究了六百多个全mtDNA基因组,结论是有一定说服力的。与此帖有关,我把它的两张图摆在下面。
文献[9]:Beringian Standstill and Spread of Native American Founders
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0000829  

文献[9]图1:Schematic representation of phylogeny of human mtDNA outside of Africa.
  Branches encompassing Native Americans and their immediate Asian ancestral and sister lineages, represented by complete sequences, are shown in black with coalescence ages indicated and geographic location identified by colours. Lineages in brown correspond to the main haplogroups, found in Eurasia and Oceania, but absent in Native Americans. For complete phylogenetic tree see Supplementary figure 1.

journal.pone.0000829.g001-1.jpg
2018-1-7 13:12
文献[9]图2:Schematic illustration of maternal geneflow in and out of Beringia.    Colours of the arrows correspond to approximate timing of the events and are decoded in the coloured time-bar. The initial peopling of Berinigia (depicted in light yellow) was followed by a standstill after which the ancestors of the Native Americans spread swiftly all over the New World while some of the Beringian maternal lineages–C1a-spred westwards. More recent (shown in green) genetic exchange is manifested by back-migration of A2a into Siberia and the spread of D2a into north-eastern America that post-dated the initial peopling of the New World.

journal.pone.0000829.g002-1.jpg
2018-1-7 13:13
估计大部分证据至今依然静静的躺在海底的‘白令古陆’...
物格而后知至,知至而后意诚,意诚而后心正,心正而后身修,身修而后家齐,家齐而后国治,国治而后天下平...
Beringian Standstill 现在没有人反对,现在有争议的是long term还是shor term.

long term 是整个LGM期间都在Beringia, 直到到14-13kyBP南下通道可以通过,再迁移到美洲; short term是LGM以后温度上升才来到Beringia,再往南没路了,冰川虽然开始融化,但还没有通道可以允许南下,那就在Beringian短期停留了,到南下通道开通再南下。

至于back-migration,  也没什么意义, 因为肯定还有留在Beringia没有南下的人群,到11-10kyBP,海水淹没了所谓的“桥”,在海峡西边的原Beringia人群,自然就留在西伯利亚了,那就是所谓back-migration。

24# cpan0256
看到一篇2006年的文章,说LGM期间阿拉斯加地区的云杉树林没有完全灭绝。看来LGM期间白令地区存在人群可用的避难地。

这文章研究了北美24个地点的云杉树叶绿体DNA,发现在阿拉斯加地区多样性相对最大。摘要里有这样的话:“We sequenced chloroplast DNA (cpDNA) of white spruce (Picea glauca), a dominant boreal tree species, in 24 forest stands across northwestern North America. The majority of cpDNA haplotypes are unique, and haplotype diversity is relatively high in Alaska, arguing against the possibility that this species migrated into the region from areas south of the Laurentide Ice Sheet after the end of the last glaciation. Thus, white spruce apparently survived long glacial episodes under climatic extremes in a heterogeneous landscape matrix.”

文章题目:Ice-age endurance: DNA evidence of a white spruce refugium in Alaska
全文链接:http://www.pnas.org/content/103/33/12447.full

下面是文章里的两张图。
图1(a):  Sampling locations and haplotype diversity of white spruce. (a) Locations of Alaskan (red) and non-Alaskan (blue) populations sampled for this study (all 12 non-Alaskan populations are outside the boundary of Beringia).


F1a.jpg
2018-1-7 14:03



图2: Haplotype network assembled by using the method of Templeton et al.[13]. Each haplotype is represented by a number–letter combination; red haplotypes occur only in Alaskan populations, blue haplotypes occur only in non-Alaskan populations, and white haplotypes occur in both regions. Circle sizes are proportional to haplotype frequencies in all 24 populations, with the largest circle representing the most abundant haplotype.

F2.large.jpg
2018-1-7 14:03
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本帖最后由 tosylate 于 2018-1-7 23:03 编辑

这些都是间接证据,在LGM时代, 和beringia差不多或更好一些植被的地方,即使在西伯利亚也有不少,从图上看,beringia沿海一带是tundra, 堪察加西侧到库页岛直到外满州,是steppe tundra,  这两哪个比较适合避难所,我猜是后者,  24kyBP的mal'ta boy , 就在另一侧steppe tundra(从贝加尔西直到西欧)。

28# cpan0256
Last_glacial_vegetation_map.png
从这个LGM时期的植被看,EA 和ANE之间的确有难以逾越的地理隔阂,有兰色的polar desert和土黄色的temperate desert。

最窄的地方是西伯利亚中部,那两块淡粉红色的steppe tundra之间, 有可能在那里,ANE向东穿过来,如果时间是这篇新文章中说的25-20ka (这个缩写好像不统一,还有kya, kyBP),  那么ANE首先遇到EA,不是在beringia, 而是在太平洋沿岸的这一条steppe tundra 。
更正一下,Yana River sites的时间是32kyBP。

盛冰期LMG的时间段,我开始还以为是个点,但后来意识到是一个时间段,好像也没有一个准确的说法,有可能各地情况不一样,  我见到有30-16kyBP, 也有 27-21kyBP, 也有下限是19kyBP的。
long-term Beringian standstill model, 所谓长期白令滞留模型, 有其合理性,在30kyBP的yana river 遗址, 虽然没有人骨,但有明确无误的人工制品,如果假设不是西伯利亚丹人的,那就是智人曾经在Beringia活动的证据 ...
tosylate 发表于 2018-1-7 10:13
反过来一看咱们中国的田园洞人DNA测完了之后得出的结论就有意的简单了,想想看,假设这个推论没有错,印第安人是3万6千年左右与东亚人群分离的,ANE和EA成分有关。而田园洞人四万年前的推测时间也没有错,而且与今天的一些美洲印第安人和某个石器时代的欧洲古人类遗址有亲缘关系,那么说明了一个什么问题呢?
田园洞应该是测人骨的C14,  这个方法,我记得上限是6-7万年,当然测出来的还要校正,比实际年份要少大概10%, 田园洞是4万年,用这个方法应该是可靠的。

这篇文章中,ancestral native american的EA 源头,说是36 ± 1.5 ka与EA主力分离, 这个时间,应该是根据mutation rate估计出来, 其准确性, 我看够呛,  好像不少以前用这个方法估算年代的文章,错误不少,甚至闹出笑话。
反过来一看咱们中国的田园洞人DNA测完了之后得出的结论就有意的简单了,想想看,假设这个推论没有错,印第安人是3万6千年左右与东亚人群分离的,ANE和EA成分有关。而田园洞人四万年前的推测时间也没有错,而且与今天 ...
wanhuatong 发表于 2018-1-9 18:41
36 ± 1.5 ka,基本上与田园洞是同期了,难道那时EA就成型了?  EDAR就出现了?  好像那里不对。
http://www.theguardian.com/scien ... -ancient-beringians

Surprise as DNA reveals new group of Native Americans: the ancient Beringians
Genetic analysis of a baby girl who died at the end of the last ice age shows she belonged to a previously unknown ancient group of Native Americans

A baby girl who lived and died in what is now Alaska at the end of the last ice age belonged to a previously unknown group of ancient Native Americans, according to DNA recovered from her bones.

The child, a mere six weeks old when she died, was found in a burial pit next to the remains of a stillborn baby, perhaps a first cousin, during excavations of an 11,500-year-old residential camp in Tanana River Valley in Central Alaska. The remains were discovered in 2013, but a full genetic analysis has not been possible until now.

Researchers tried to recover ancient DNA from both of the infants but succeeded only in the case of the larger individual. They had expected her genetic material to resemble modern northern or southern lineages of Native Americans, but found instead that she had a distinct genetic makeup that made her a member of a separate population.

The newly-discovered group, named “ancient Beringians”, appears to have split off from the founding population of Native Americans about 20,000 years ago. While the ancestors of other Native Americans pushed south into the continent as the ice caps thawed, the ancient Beringians remained in the north until they eventually died out.

“This is a new population of Native Americans,” said Eske Willerslev, an evolutionary geneticist at the University of Copenhagen, whose team recovered the girl’s DNA from a dense part of her skull known as the petrous bone. Details of the work are published in Nature.

Working with scientists at the University of Alaska and elsewhere, Willerslev compared the genetic makeup of the baby, named Xach’itee’aanenh t’eede gaay or “sunrise child-girl” by the local community, with genomes from other ancient and modern people. They found that nearly half of the girl’s DNA came from the ancient north Eurasians who lived in what is now Siberia. The rest of her genetic makeup was a roughly even mix of DNA now carried by the northern and southern Native Americans.

Using evolutionary models, the researchers showed that the ancestors of the first Native Americans started to emerge as a distinct population about 35,000 years ago, probably in north-east Asia. About 25,000 years ago, this group mixed and bred with ancient north Eurasians in the region, the descendants of whom went on to become the first Native Americans to settle the New World.

During the last ice age, so much water was locked up in the ice caps that a land bridge reached from Asia to North America across what is now the Bering Strait. Willerslev believes the ancestors of Native Americans travelled to the continent in a single wave of migration more than 20,000 years ago. Those who settled in the north became the isolated ancient Beringians, he said, while those who moved south, around or through the ice sheets, split into the north and south Native Americans about 15,700 years ago.

But there is another possibility. Ben Potter, an archaeologist on the team from the University of Alaska in Fairbanks, suspects that the Beringians split from the ancestors of other Native Americans in Asia before both groups made their way across the land bridge to North America in separate migrations. “The support for this scenario is pretty strong,” he said. “We have no evidence of people in the Beringia region 20,000 years ago.”

The families who lived at the ancient camp may have spent months there, Potter said. Excavations at the site, known as Upward Sun River, have revealed at least three tent structures that would have provided shelter. The two babies were found in a burial pit beneath a hearth where families cooked salmon caught in the local river. The cremated remains of a third child, who died at the age of three, were found on top of the hearth at the abandoned camp.

Connie Mulligan, an anthropologist at the University of Florida, said the findings pointed to a single migration of people from Asia to the New World, but said other questions remained. “How did people move so quickly to the southernmost point of South America and settle two continents that span a huge climatic and geographic range?” she said.

David Reich, a geneticist at Harvard University, said the work boosted the case for a single migration into Alaska, but did not rule out alternatives involving multiple waves of migration. He added that he was unconvinced that the ancient Beringian group split from the ancestors of other Native Americans 20,000 years ago, because even tiny errors in scientists’ data can lead to radically different split times for evolutionary lineages. “While the 19,000-21,000 year date would have important implications if true and may very well be right, I am not convinced that there is compelling evidence that the initial split date is that old,” he said.
有意思的是后面几段。考古学家不敢苟同,“We have no evidence of people in the Beringia region 20,000 years ago.”

最后一段是同行大牛David Reich, 也表示时间不足信,“even tiny errors in scientists’ data can lead to radically different split times for evolutionary lineages”。
有意思的是后面几段。考古学家不敢苟同,“We have no evidence of people in the Beringia region 20,000 years ago.”

最后一段是同行大牛David Reich, 也表示时间不足信,“even tiny errors in scientists’  ...
tosylate 发表于 2018-1-10 04:48
关于David Reich对分化时间产生的疑问,我认为目前通过常染计算得到的结果可能远不如Y染色体计算的结果可靠。这样我们可以通过目前美洲土著的Y染数据对这些分化时间进行分析。

目前美洲的土著的父系主要来自三个主要分支,Q-Z780(这也是Anzick人的类型)、Q-M3C-P39。其中Q-Z780Q-M3同属于Q-L54下游。该支系下游还包括众多分布在旧大陆的分支,共祖时间大约在16200年前。

如果我们假设这一父系在进入古代美洲祖先人群后没有回流的话(目前尚见不到这一迹象)。那么现代美洲人群父系与现代旧大陆支系分开的时间当在16200年之后。如果我们认为现代美洲人群的ANE成分来自Q-L54父系所代表的人群的话。那么便与文章中认为ANE成分进入美洲土著祖先人群的时间在2.52万年前相悖。这个时间甚至晚于文章判断南北美洲人群彼此分化的时间。那么便有两种可能。

a.
如果选择相信文章中所判断的分化时间,那么在2.52万前融入美洲祖先人群的ANE人群的父系就并不属于现代美洲土著的世系,并在后来消失了。现代美洲人群的父系是在1.6万年之后融入“古白令人”并比较彻底的取代了其原有的父系。


b.
如果我们相信文章所提供的人群间分化关系,并且认为是现代美洲人群父系Q-L54带来了ANE成分。那么其融入美洲土著人群的时间应修正为16.2ka左右到M3分化的13.7ka左右之间。也就是说在16.2ka之后,文章中所说的“古白令人群”才有形成的机会。


从目前的情况看后一种情况的可能性要大于第一种。

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  • Ryan

C-M130交流群:542136235
本帖最后由 豢龙氏 于 2018-1-11 09:33 编辑

关于北美美洲人群中的C-F3918-P39,明显与文章中所指在11.5ka之后融入北美美洲人群的东欧亚成分密切相关。这一成分与Athabascans(属纳-德内语系)族群相关,而我们知道,C-P39在北美的分布与纳-德内语系族群同样有着密切的相关性。同时文章认为这一成分与Koryaks族群关系最近,而Koryak族群中也发现了F3918的一个早期分支。
由此,我认为基本可以判断,是P39父系所代表的这个族群在1.15万年后向北美土著人群中又注入了新的遗传成分。
C-M130交流群:542136235
关于David Reich对分化时间产生的疑问,我认为目前通过常染计算得到的结果可能远不如Y染色体计算的结果可靠。这样我们可以通过目前美洲土著的Y染数据对这些分化时间进行分析。

目前美洲的土著的父系主要来自三个 ...
豢龙氏 发表于 2018-1-10 12:51
如果是long-term Beringian standstill model,那由于长时间的瓶颈会抹杀掉始祖分支,你对a的评判不再成立。
O3a3c* (M134+, M117-)
田园洞人的年代考古上曾有争议,有说法是一万年左右。但它的mt相当古老,不知是不是同一批骨头。
O3a3c* (M134+, M117-)
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