Unravelling early human migration in southern South America using Darwin's Fuegian lice

大约15,000年前，部落从西伯利亚进入美洲.这些部落沿着美国西海岸一直延续到遥远南部的火地岛。在比格尔号的航行中，查尔斯·达尔文从两个人类群体--富伊吉安人和乔诺斯人身上感染了虱子。这些虱子与现代虱子不同，它们仍然含有印第安人的血液。达尔文来访后不久，这些部落就灭绝了。达尔文、华莱士和其他人从灭绝的人类部落、塔斯马尼亚狼等灭绝的动物和更多的动物中收集到的虱子总共约3000个标本。它们目前收藏在牛津大学自然历史博物馆的丹尼虱子藏品中。然而，没有这些虱子的目录，甚至连总数都不知道，而且大多数标本从未被鉴定过。这些标本本身正处于永远消失的边缘。我们建议拯救和管理丹尼的收藏，让这些虱子和它们携带的血液(来自灭绝的宿主)提供给科学界和公众。使用在40万年前的人类骨骼上成功的先进的古代DNA方法，我们建议对180岁的达尔文虱子和这些虱子内血粉的人类线粒体进行遗传分析。我们已经识别出一个现代的、但偏远和孤立的中美洲部落，目前携带头虱物种假人毛虱和南美部落，携带不同核型(染色体数量)的新虱子物种。假人疟原虫也曾在波利尼西亚印第安人和猴子中被描述。通过对这两种现代虱子进行测序，并将它们与黑猩猩和黑猩猩P·舍菲的虱子进行比较，以及与福伊吉亚和乔诺斯虱子的结果进行比较，我们的目标是追踪人类在南美洲的迁徙，并揭开虱子是从灵长类动物传播到人类还是反之亦然。例如，我们的阴虱很可能是我们的祖先从大约300-400万年前被猎杀的大猩猩那里获得的。现代人现在头上携带的虱子可以分为三个分支(基因群)。A分支分布在非洲和世界其他地区，B分支分布在欧洲、美洲和澳大利亚，C分支分布在埃塞俄比亚、塞内加尔和尼泊尔。使用单个线粒体基因片段，人们估计A支和B支的谱系在70万到120万年前分离，而C支大约在200万年前分裂。这些大范围的估计没有帮助，因为它们不能告诉我们这些虱子是从谁那里来的。分支A和B的虱子，他们是来自尼安德特人、丹尼索瓦人、直立人还是来自H？C分支虱子的年龄估计是如此模糊，以至于我们甚至无法做出有用的猜测。A分支虱子的基因组已经被测序。我们建议确定B分支和C分支虱子的遗传序列，以获得对虱子谱系分裂的尽可能准确的时间估计。虽然揭开人类虱子的系统发生学很有趣，但重要的是我们携带了所有这些虱子，这证明了现代人的血统与这些古人类有过身体接触，例如直立人。虱子不能在离开宿主几个小时后存活，所以古人类和现代人的血统或物种必须在时间和空间上重叠才能物理地交换虱子。这种身体接触来交换活着的头虱是一个独特的特点。没有交配的证据和接触的时间无法从任何人类测序中检索到，无论是古代的还是现代的，只能从虱子中检索到。这项建议旨在确定我们过去与哪些古老的人类血统或物种有过身体接触，以及在什么时候。因为此刻我们头上有三个不同的虱子分支，我们一定与其他人类血统有过两次不同的遭遇，相隔大约一百万年。

Some 15,000 years ago, tribes entered America from Siberia to people the Americas. These tribes continued along the west coast of America until they reached the small islands of Tierra del Fuego in the far South. During his voyage on the Beagle, Charles Darwin obtained lice from two human groups, Fuegians and Chonos. These lice are different from modern lice and they still contain the blood of the Indians. These tribes went extinct soon after Darwin's visit. Lice collected by Darwin, Wallace and others from extinct human tribes, extinct animals like the Tasmanian wolf and many more animals, total some 3000 specimens. They are currently in the Denny lice collection of the Natural History Museum, University of Oxford. However, there is no catalogue of these lice, not even the total number is known, and most specimens have never been identified. The specimens themselves are at the point of being lost forever. We propose to rescue and curate the Denny collection, to make these lice and the blood they carry inside (from extinct hosts) available to the scientific and public community. Using advanced ancient DNA methods that have been successful on a 400,000 year-old human bone, we propose to carry out genetic analyses on the 180 year-old Darwin lice and the human mitochondria of the blood meal inside these lice.We have identified a modern, but remote and isolated Central American tribe currently carrying the head louse species Pediculus pseudohumanus and a South American tribe carrying a new species of lice with a different karyotype (number of chromosomes). P. pseudohumanus has also been described from Polynesian Indians and monkeys. By sequencing these two modern lice species and comparing them with the louse of chimpanzees and bonobos, P. schäffi, as well as with the results of the Fuegian and Chonos lice, we aim to trace human migration in South America and unravel whether lice jumped from primates to humans or vice-versa. Our pubic lice, for example, have likely been acquired by our ancestors from gorillas, hunted about 3-4 million years ago.The lice that modern humans carry at present on their heads can be divided into three clades (genetic groups). Clade A is found in Africa and rest of the World, B in Europe, America and Australia, and C in Ethiopia, Senegal and Nepal. Using a single mitochondrial gene fragment, it has been estimated that the clade A and B lineages separated between 700,000 and 1.2 million years ago and that clade C split around 2 millions ago. These large range estimations are not helpful because they do not tell us from whom these lice came. Clade A and B lice, did they come from Neanderthals, from Denisovans, from Homo erectus, or from H. antecessor? The age estimation of clade C lice is so vague that we cannot even make a useful guess. The genome of clade A lice have already been sequenced. We propose to determine the genetic sequence of clade B and C lice to obtain a time estimate as precise as possible for the split of the lice lineages. While it would be interesting enough to unravel the phylogenomics of human lice, the importance lies in the fact that we carry all these lice, which proves that the modern human lineage had physical contact with these archaic humans, e.g. H. erectus.Lice cannot survive for more than a few hours off their host, so archaic and modern human lineages or species had to overlap in time and space to physically exchange their lice. This physical contact to exchange living head lice is a unique feature. Evidence about contact with no interbreeding, and the time of contact cannot be retrieved from any human sequencing, ancient or modern, only from lice. This proposal aims to identify with which archaic human lineage or species we had physical contact in the past and when. Since at the moment we carry three different clades of lice on our heads, we must have had two separate encounters with other human lineages, separated by roughly one million years