Certainly, mtDNA and Y Chromosome material (not to mention autosomal traits) need to be taken into consideration.

And then, there's the difficult question of what exactly is meant by "Rus," as different ancient sources don't completely agree.

A lot depends on how far back you go, in order to answer the question. Proto-Slavic is much closer to Sanskrit, Greek and Latin than Proto-Celtic, but Proto-Slavic is closer to Proto-Celtic than Greek or Latin are (don't know offhand about Proto-Celtic vis-a-vis Proto-Sanskrit).

The very first people seen in archaeological evidence in Europe are from the territory generally regarded as "Rus" or "Sclaveci" territory - although it's difficult to say (at 45,000BP) who these people were. One thing that's interesting about them is that once they inhabit the Crimea (with redundant and well stocked settlements), they head north - becoming the first people to see the Baltic or the North Sea, and ending up with some very interesting settlements near Pskov by 40,000BP - and later adopting a lifestyle that moved north or south depending on where the ice sheet was (living on tundra part of the year).

They had ladders when they came; they were making maps earlier than any other people I know about. Very interesting - and since they are trekking from Kiev and Crimea to Pskov and back for thousands of years, I pretty much can't avoid thinking of them as the ancestral population for what we later call the Rus.

Personally, I think they had kayak like boats by 30,000 years ago, as the settlements along the North Sea and the Baltic are about the distance you'd expect someone to paddle in a day. They end up in Altai (and Ireland and Japan) by 28,000BP - same culture, same petroglyphs, same pit houses, same giant wooden tongs, same use of ladders, same types of sewing techniques, same physiognomy.

Norway and Sweden are still empty at that point (and will remain covered with an ice sheet for most of the ensuing 16,000 years).

Oh, and they had harpoons, incredibly great sinew-working ability, and are related to the people who first invented string (they already had rope at 40,000BP - these early occupants of what is now prime Russian territory).

By 28,000 BP, it's clear that many different European subcultures were evolving, but the petroglyphs from Crimea and Kiev tie those cultures to Southern France. Since I believe these folks had boats, I'm also giving them credit for being the first people in the British Isles (28,000BP, in Wales, arrived with an entire array of woodworking tools and very well-thought out survival practices).

These are the Aurignacians of course that I'm speaking about, and while it used to be thought they came in through the Southern Pontic region, that hypothesis seems unsupported - it was a Northern Pontic route.

The men likely would have had the I form of the Y chromosome and the women the U form of mtDNA which mutated to X after they came to Europe.

Even today, one finds a bit of that ancient DNA in modern Russia (and in the case of U mtDNA, quite a bit of it remains).