Below maps were added to the http://www.imperialchina.org/Barbarian.htm which was embedded within the http://www.imperialchina.org/Huns.html and http://www.imperialchina.org/Turks_Uygurs.html pages. On basis of new archaeological findings and historical Chinese records, I will tentatively speculate as to when the east met with the west.   First I want to debunk the fallacies in regards to the equation of the ancient Yu-shi tribe to the Yuezhi, and the speculation on the jade trade that the Yuezhi was falsely accredited with.   See Barbarians.htm for more discussions on forged statements in Guan-zi [管子] (which historian Ma Feibai pierced sentence by sentence). Around Xin (New) Dynasty (AD 6-23), there occurred a forgery movement by Chinese scholars, possibly with the intention of substantiating the mandate of the usurper Wang Mang's dynasty. The classics which were proved to be forgeries include "Guan-zi [管子]", which historian Ma Feibai pierced sentence by sentence. Using Ma's same logic, I had found the two other books, "Yi-zhou-shu" [逸周书] or "Zhou-shu" (Zhou Dynasty [16th cen. B.C. - 256 B.C.] [abbrev. 周书] book, not the Zhou-shu [周书] from Posterior Zhou Dynasty of the South-North Dynasty time period of AD 557-581) and "Shang[1]-shu" [商书] (Shang Dynasty [16-11th cent. B.C.] book, not Shang[4]-shu [尚书], i.e., remotely ancient book which was said to be abridged by Zuo Qiuming), to be written in the exact same style and could be forgeries by possibly the same person. Discarding the forgery of Guan-zi [管子] basically eliminated the whole foundation upon which the existence of the Yuezhi and the jade trade was built, a fallacy which was widely cited in the most recent 10-20 years, i.e., 1990s and 2000s, to the effect that the fabricated Yuezhi had lived close to the heart of China, playing the role of bearing the Aryan civilization to China. (A recent writing on ancient forgeries at the imperialchina.org blog, which was not in the sense of political correctness till later Western Han Dynasty, is available in pdf format: ImperialChinaOrg-on-forgeries.pdf.) I never thought the people of the Central Asia or in Chinese Turkestan were an intermediary form of human evolution, which was my basis of calling the Siberian origin of Koreans by a 'moo' point. I constantly pointed out that in the collective memory of Sino-Tibetan, that passed down by generations, the Sinitic Chinese had forgot they travelled north from today's Vietnam while claiming a walk down Mt Kunlun. Previously, I checked the historical context as well as the geo situation to find out when the east met with the west, and believed that the Hun-Yuezhi War could be the start of the contact. With new archeological findings, I would add that the proto-Tibetan Qiangs had indeed penetrated into Chinese Turkestan, to the north side of Mt Tianshan, from perhaps the southeastern rim of the Taklamakan Desert.   Click on the below picture for the enlarged map showing the first Hunnic attack at the Yuezhi around the ancient Juyan Lake (also known as the West Sea in Chinese classics, and later known as the Kharakoto [Blackwater] Lake) in the 3rd century B.C., and the subsequent Hunnic attack at the Wusun/Loulan near Yiwu in the 2nd century B.C., to the east of Turpan, which triggered the Wusun migration to Ili where they further drove the Yuezhi towards today's Afghanistan. (See Barbarians.htm for more discussions on the Yuezhi migration timeline.) On the modern map, there was a tiny corridor between Chinese Turkistan and China, which was the narrow strip of sand to the east of Hami. However, this corridor could be a recent event. There was the historical DAZI blackhole desert to the east, nowadays called by the generic name GOBI. The ancient Mongoloid migration into Tianshan Mountain could have come north from south, i.e., the Tibetan Plateau/Ruoqiang direction to the south --though I hesitated about the passibility of the "Liu-sha" flowing sand desert between Ruoqiang and Loulan (Lop Nur), which was another tiny corridor noticeable on the modern map.   Judging from Han Dynasty emissary Zhang Qian's change of mind on his return trip to go home along the Hami strip rather than going straight east across the Qiang-zhong or the middle Qiang nation land, we could tell that the northern strip was perhaps the most traveler-friendly. (Could Zhang Qian change his mind in the hope of sneaking into the Hunnic territory to see the child he had with the Hun woman?) That was Han Emperor Wudi's reign of B.C. 140-86, i.e., 140 BC and later, much later than Hun-Yuezhi wars.   Now, let's talk about human migration. There were widespread discussions of 'Caucasoid' mummies in Chinese Turkestan, with 'Loulan Beaty' purportedly dated 2000 B.C., while the southern 'cousins' in Khotan area dated 100-300 B.C. The timeline suggested a move from north to south, not west to east. The 2000 B.C. Caucasoid mummies found in Loulan, in the Turpan Depression/Kumtag Desert, in-between Altaic/Tianshan Mountains and the Altun Mountain (Ruoqiang), could be the Indo-European people coming from the north of the Altaic Mountain [the Mongol Altaic Mountain of today], near the Alfanesevo bronze culture. Yuezhi could be of this group of people coming from north. Further diggings in Loulan area, i.e., the ancient Salty Lake and Salty River (Peacock Rover), led to a site called by Xiaohe or the Little River, next to the Salty River (Peacock Rover), where Mongoloid Mummies were discovered. It appears to me there was indeed good carbon dating on Xiaohe excavation, saying "The entire necropolis can be divided, based on the archeological materials, into earlier and later layers. Radiocarbon measurement (14C) dates the lowest layer of occupation to around 3980 ± 40 BP (personal communications; calibrated and measured by Wu Xiaohong, Head of the Laboratory of Accelerator Mass Spectrometry, Peking University), which is older than that of the Gumugou cemetery (dated to 3800)." The article claimed that the 'Mongoloid' mtDNA had similarity to some present South Siberian population. (For details, check http://www.biomedcentral.com/1741-7007/8/15 for the full article "Evidence that a West-East admixed population lived in the Tarim Basin as early as the early Bronze Age".)   The linking of this certain mtDNA in Xiaohe/Loulan area to a modern Siberian population could be said to be circumvential at best since a lot of things had happened in the past 2-3000 years. It kind of had the same timing as the Mongoloid mummies that were discovered to the north and east of the Tianshan Mountain. More than what was found about the mtDNA at Xiaohe/Loulan, there were mummies of Khams Tibetan type found to the further north, at the Tianshan-Altaic mountain areas, which presented a much more convincing point that the proto-Tibetan Qiangs had indeed crossed over the strip of the sand desert near Loulan to reach the north side of Tianshan. Possibly, the Khams [proto-]Tibetan, after reaching Tianshan Mountain Range, moved towards Hami (Qumul) to the east, where there were the Hami (Qumul) Mongoloid mummies excavated. Note that today's Kham Tibetans were not far away from the historical Sanxingdui (three star) Excavations in western Sichuan, that was discovered by Gaway Hann (an American professor of the former Huaxi University), a Neolithic/Bronze culture dating from about 4800 to 2800 years ago, as well as a bridge providing Southwest China's tin to the Shang dynasty and the Zhou dynasty.   My reasoning was that the Qiangs had a dominance in the area since China's prehistory, like 5000 years ago, at least the time of the Yellow Emperor [Huangdi (l. BC 2697 - 2599 ?)], and they controlled the southern rim, southeastern rim and western rim of the Taklamakan Desert, and somehow around 2000 B.C., penetrated northward to reach the two sides of the Tianshan mountain range, while the so-called Caucasoid oases in their path, namely, the Loulan area, might have risen and fallen numerous times in history -- if they ever existed there prior to the penetration by the Khams [proto-]Tibetans. Or the other way around, the Khams [proto-]Tibetans could be speculated to have penetrated to the two sides of the Tianshan mountain range earlier than the Indo-Europeans, and subsequently encountered the Indo-Europeans near the Tianshan Mountain, and ultimately the Indo-Europeans gradually dominated over the area and eliminated the trace of the Khams [proto-]Tibetans, pressing them back to the southeastern rim of the Taklamakan Desert. (See Barbarians.htm for more discussions on the ancient human migrations.)   There was a striking similarity between the Mongol attack at the Tanguts in the 13th cent. A.D. and the Hun attack at the Yuezhi in the 3rd cent. B.C. Both took the desert road towards the Blackwater Lake. It kind of gives you a picture how the Huns first raided to the west against the Yuezhi, forcing the Yuezhi Major to flee west while the elderly and the children, i.e., the Yuezhi Minor, crossed the Qilian mountain to seek asylum with the Qiangs, and per Yu Taishan, continued to move on towards the southeastern rim of the Taklamakan Desert, towards Khotan where the people were recorded to be Mongoloid, i.e., Hua-xia-looking, throughout China's Han and Tang dynastic records, till annihilated sometime during the Islamic invasion of the Buddhist stronghold of Khotan or possibly during the earlier Turkic-Uygur conquest of the Chinese Turkistan. Note the discovery of the so-called 100-300 BC Caucasoid in Khotan, which matched with the escape timeframe of the Yuezhi Minor. (Another recent writing on Zhou King Muwang's travelogue at the imperialchina.org blog, is available in pdf format [Mu-tian-zi.pdf], exhibited the westernmost extent of the ancient Chinese kingdom to be no more than the edge of the Kumtag Desert and right at the Black Water Lake.)