Valter Lang (of University of Tartu) posits that the Baltic Finns and the Sámi were already separate linguistic groups before they left the Uralic core area, and arrived to Fennoscandia via different routes.
In contrast, Baltic Finns took a southern route from the Daugava river (in today's Latvia) to northern Estonia and over the sea into western Finland.
Local (in Sápmi) ancestors of the modern Sámi people likely still spoke non-Uralic, "Paleoeuropean" languages at this point (see Pre-Finno-Ugric substrate).
Evidence also can be found for the existence of language varieties closely related to but likely distinct from Sámi proper having been spoken further east, with a limit around Lake Beloye.
Concurrently, Finnic languages that would eventually end up becoming modern-day Finnish and Karelian were being adopted in the southern end of the Proto-Sámi area, likely in connection with the introduction of agriculture, a process that continued until the 19th century, leading to the extirpation of original Sámi languages in Karelia and all but northernmost Finland.
The Proto-Sámi consonant inventory is mostly faithfully retained from Proto-Uralic, and is considerably smaller than what is typically found in modern Sámi languages.
There were 16 contrastive consonants, most of which could however occur both short and geminate: Stop and affricate consonants were split in three main allophones with respect to phonation: The spirant *δ also had two allophones, voiceless [θ] occurring word-initially and syllable-finally, and voiced [ð] elsewhere.
In this article, when it is relevant and necessary to show the distinction, the weak grade is denoted with an inverted breve below the consonant(s): s : s̯, č : č̯, tt : t̯t̯, lk : l̯k̯.
After the phonematization of gradation due to loss of word-final sounds, Sámi varieties could be left with as many as four different contrastive degrees of consonant length.
Weakening and simplification of non-final consonants after unstressed syllables contributed further to the alternation, leading to differences that are sometimes quite striking.
Nominals, i.e. nouns, adjectives, numerals and pronouns were systematically inflected for two numbers and ten cases.
One oddity is that the plurality of words, 35 percent are of uncertain origin, likely from a theorized group of languages called Proto-Laplandic.
Words describing natural elements such as reindeer or snow tend to be from of unknown origin but those for more modern things such as tools contain larger Germanic influence.
This approximate point of Pre-Sámi marks the introduction of the oldest Western Indo-European loanwords from Baltic and Germanic.
Likely contemporary to these were the oldest loanwords adapted from extinct Paleo-European substrate languages during the northwestward expansion of Pre-Sámi.
The previous changes left a system consisting of *i *e *ä *a *o *u in the first syllable in Pre-Sámi, and probably at least long *ī *ē *ū.
Sammallahti (1998:182–183) suggests the following four phases: The inventory of long vowels in stressed syllables now featured seven members: *ī *ē *ɛ̄ *ā *ɔ̄ *ō *ū.