@Johen
Grigoryev wrote the following:
[...settlements with round plan, ceramics with roller, bone plate armours, developed metallurgy and domesticanimals.During XVI-XV centuries artefacts closely related to Seyma tradition became typical for hoards in Pannonia, France and England. Thus, these bronzes distribution marks the moving of Celts.A new wave of newcomers left F’odorovo culture sites. Some include usually this culture, together withAlakul culture, in Andronovo culture. However, all attempts to find its local roots had no success. But theseroots are in North-Western Iran and South Azerbaijan: cremation in stone boxes and cysts under mounds, clayprops for hearth, oval dishes, polished ware. Complex of metal have analogies in Circumpontic area, but first ofall, in Sumbar culture in South-Western Turkmenistan. Potteries from Central Asia have been found in someF’odorovo sites.Typical F’odorovo artefacts are known up to Dnieper river. However, a contact of F’odorovo tribes withfirst wave of newcomers is more important for us. As a result of this contact new cultures were formed, whichfix this contact and a gradual displacement of these populations to the West: Chernoozerie in Irtish basin,Cherkaskul in the Urals, Suskan and Prikazanskaia in Volga-Kama region, Pozdniakovo in Oka basin. Thesecultures combine cremation and inhumation, mounds and flat burials, bronzes of Seyma and F’odorovo types.Next moving of these tribes to the West leads to forming of Sosnitzkaia culture on the left-bank ofDnieper, Trzciniec-Komarov culture from Dnieper to Vistula and Tumulus culture in Central and NorthernEurope. These cultures reflect localisation of Balts, Slavs and Germans...]
Ancient scholars spoke of possible influences from Siberia and even China upon La Tène; and of strong Scythian technics influences upon the same La Tène; but it's very later than the 16th/15th Centuries BC. But cultural or technical input is not by force an ethnic one. That said the 15th Cy could correspond to the Tumuli culture of Bavaria and Central Europe which is seen as Celtic or Italo-Celtic by a lot of people; Personally I think proto-Celts are older than Tumuli, and linked to Y-R1b-P312. It would not be the first time that some foreign newcomers integrated and even dominated other culture, forming the elite with new artefacts, despite forming only a minority concerning number and loosing its proper language and demic input after some later generations - the mysterious "Illyrians" did maybe the geographical link between Celto-Italics and Steppes of the time? By instance, the "Celtic" Hallstatt elite of Wurttemberg/Bavaria showed 1/4 of physically newcomers of a mix with evident "proto-europoid" types input, maybe not too different from some 'corded' types, close to other newcomers of the same period in High-Austria, Low-Austria, Croatia, Slavonia, Hungary and Silesia; Illyrians are supposed to have cut off Celts and Italics according to some people? Or others ???
among Celts their demic input seems having merely disappeared in La Tène; maybe not their imports? There is no link to the Seyma-Turbino question but it shows demic/ethnic input can be very lighter than the cultural one. People loan and adapt. Celts were very smart at this sport.