In trying to answer the map question, it might be a good idea to stat with some Dacian history. Presumably, after Trajan conquered Dacia, the men were massacred or enslaved and the Dacian state including its capital, Sarmizegetusa, obliterated then rebuilt in Roman fashion.

Dacia’s conquest (2, 3, 4, 5) was years in the making and it helped restore a stagnating (or already declining) Roman empire to its former glory. Dacia’s huge gold reserves helped finance further conquest. So important was this conquest for Rome that it was commemorated with “Trajan’s Column” (Wikipedia, simulation, details, genocide). Within the next decade, the Roman empire reached its largest extent and soon thereafter started to decline rapidly, collapsing (the Western, mother lode part) within the next 3-4 centuries.

Most of the disputed facts refer to what has happened after the Roman retreat and until the 10th century. There is however a theory that involves what has happened long before.

protochronism

Known in Romania as Dacology, this theory posits that the Roman empire was founded and created by Dacian immigrants. Here’s Wikipedia's overview:

Also noted are the exploitation of the Tartaria tablets as certain proof that writing originated on proto-Dacian territory, and the belief that the Dacian language survived all the way to the Middle Ages.

There are even connections made to Stonehenge via the astronomic observatory and the calendar.

An additional - but not universal - feature is the attempted connection between the supposed monotheism [aka henotheism] of the Zalmoxis cult and Christianity, in the belief that Dacians easily adopted and subsequently influenced the religion. Also, Christianity is argued to have been preached to the Daco-Romans by Saint Andrew, who is considered, doubtfully, as the clear origin of modern-day Romanian Orthodoxy. Despite the lack of evidence [0, 1, 2] to support this, it is the official church stance, being found in history textbooks used in Romanian Orthodox seminaries and theology institutes.

LE: It should be noted that this "universal myth ofl resurrection / Sun worship" view is also expressed and explained in Zeitgeist, and it really isn't that far-fetched. This Wikipedia article seems unduly harsh in criticizing and rejecting a theory.

My view is that this theory, espoused among others by Dr. Napoleon Savescu and Dr. G. D. Iscru, has a low chance of being true and furthermore of being accepted by other historians.

zalmoxis

There are those who doubt even Herodotus (the “father of history”), but his record is generally accepted for lack of a better one:

in book 4 of his Histories: 93. ...the Getae are the bravest of the Thracians and the justest. 94. They believe they are immortal in the following sense: they think they do not die and that the one who dies joins Zalmoxis, a divine being; some call this same divine being Gebeleizis. Every four years, they send a messenger to Zalmoxis, who is chosen by chance. They ask him to tell Zalmoxis what they want on that occasion. The sending is done in the following way: men standing there for that purpose hold three spears; other people take the one who is sent to Zalmoxis by his hands and feet and fling him and throw him in the air on the spears. If he dies pierced, the think that the divinity is going to help them; if he does not die, it is him who is accused and they declare that he is a bad person. And, after he has been charged, they send another one. The messenger is told the requests while he is still alive. The same Thracians, on other occasions, when he thunders and lightens, shoot with arrows up in the air against the sky and menace the divinity because they think there is no other god than theirs.

Such customs are hardly “enlightened”, yet in those times the Romans, not to mention other “barbarians” had similarly disturbing practices. Even in medieval times, it seems that upon election, a cardinal would check that the Pope’s testicles have descended.

According to Herodotus, the Greeks of the Hellespont and the Black Sea tell that Zalmoxis was a slave on Samos of Pythagoras, son of Mnesarchos. After being liberated, he gathered a huge wealth and once rich, went back to his homeland. Thracians lived simple hard lives. Zalmoxis having lived amongst the wisest of Greeks - Pythagoras and had been initiated to the Ionian life and Eleusinian Mysteries. Building a banquet hall, he received the chiefs and his fellow countrymen throwing a banquet, he taught that none of his guests nor their descendants would ever die, but instead they would go to a place where they would live forever in a complete happiness. He then dug an underground residence and, once finished, he disappeared from the Thracians going down to his underground residence and lived there for three years. The Thracians missed him and wept fearing him dead. The fourth year, he came back amongst them and thus they believed what Zalmoxis had told them.

There are some obvious parallels to Christ’s resurrection, but that’s not the only possible interpretation, there are others (cf. Wikipedia):

• Some authors consider Herodotus is just making fun about the Getae's barbarian beliefs;
• Some take the passage seriously, and consider Zalmoxis has created a ritual of passage; this theory is mainly supported by Mircea Eliade, who was the first to write a coherent interpretation about Zalmoxis;
• Some authors insist on Zalmoxis' relation with Pythagoras, stating that he has founded a mystical cult; partly this theory may be found in Eliade's work;
• Some see in Zalmoxis a Christ figure who dies and resurrects; this position was also defended by Jean (Ioan) Coman, a professor of patristics and orthodox priest, who was a friend of Eliade and published in Eliade's journal "Zalmoxis", which appeared in the 1930.

Apart from Herodotus’ possibly disparaging view of Zalmoxis, others make some interesting connections.

It is difficult to define the time when a cult to Zalmoxis may have existed. It is just sure that it must be anterior to Herodotus' work. It seems that some people have considered that the archaism of Zalmoxis's doctrine points out to an heritage from before the times of Indo-Europeans, which is nevertheless quite difficult, if not impossible, to demonstrate.

Plato says in the Charmides dialogue 156 D - 157 B that Zalmoxis was also a great physician who took a holistic approach to healing body and soul (psyche).

As interesting and controversial as Zalmoxis’ cult is, it does not shine much light over where did the Romanians form as a people. The Greek connection nonetheless seems to suggest that if the people did not form in today’s Romania, it may have formed further South.

So to start answering the map question we started from, have look at this “ethnic map evolution of Romanians” as well as Timelapse of Europe changing borders and the Roman Empire Decline.

A more direct answer might be found in the first part of “Haploid M170” and, to a lesser extent, the neutr(aliz)ed history of Romanians. Let us now proceed to the gist of our (geo-linguistic) argument.

Sources / More info: Protochronism