"Around 7,000 years ago, a Stone Age culture spread across Europe, made famous by discoveries of small, rotund "Venus" figurines found in their burials. The study results suggest those people were genetically connected—one thin population of dark-haired hunter-gatherers whose domain reached from Spain to Siberia. They were also partly the ancestors of many of today's northern Europeans"
Just saying I have mtDNA U5b2a2(La Brana-1 had U5b2c1) I am very proud of my European hunter gatherer ancestry, and also my near eastern farmer ancestry.
There isn't enough ancient DNA to prove the people of Upper Palaeolithic Europe were THE ancestors of Mesolithic Europeans. They most likely did but we need ancient DNA to "prove" it. I have just begun to learn about cultures of Upper Palaeolithic Europe and it seems the same people lived there for 10,000's of years all the way up to La Brana-1. There are two pre-U5 samples from Dolni Vestonice site in Czech Republic dated to 31,155 years old(maybe that date is off) that site also had many Venus figurines and were typical Gravettian people. I have also seen a lot of evidence that MA-1 and AG2 were like the eastern branch of a huge related population that stretched from Iberian to Siberia. At the Mal'ta site I have heard there were ivory figurines of naked women similar to the ones in Europe from the Upper Palaeolithic.
"They were also partly the ancestors of many of today's northern Europeans""
True but doesn't tell the full story. Europeans like Lithuanians, Estonians, Latvians, Finnish, Russians, various Uralic and Turkic people in Russia, and Swedish-Norwegian probably trace the majority of their ancestry to these hunter gatherers. In central Europe, British isles, and eastern Europe(Balkans-) they may also have majority hunter gatherer ancestry and if not majority close to 50%. Percentages vary in southern Europe in Iberia and Balkans(Greece-) it could be as high as 30-40% or as low as something like 20%, French are very intermediate between north-west Europeans and Iberians the further south the more similar to Iberians the further north the more similar to north-west Europeans. In Italy(lower the more south you go), Greece, and Sardinia hunter gatherer ancestry I don't know is maybe something like 10-30%.
My estimates were based on an admixture made by Laz 2013. WHG-EEF-ANE. WHG is based on ~8,000 year old hunter gatherer from Luxembourg, EEF is based on ~7,500 year old farmer from Germany, ANE is based on ~24,000 year old MA-1 boy from Siberia.
No one knows what the origin of unique pigmentation in Europe is. Ancient DNA has found that the mutations most associated with European light skin came with near eastern farmers(they are near eastern not European), light eyes existed and were probably popular in hunter gatherers, hunter gatherers likely had dark skin but skin color is still unknown, farmers likely had skin tone like modern southern Europeans(especially Sardinians who are almost no different genetically), both farmers and hunter gatherers were likely mainly black(or at least dark) haired.
The main think that connects north Europeans and makes them distinct from south Europeans is more hunter gatherer ancestry even though those hunter gatherers in the last 10,000 years may have been totally dark haired, dark brown skinned, and blue eyed. A lot can change through selection of genes in 10,000 years. The paleness(not counting light eyes and probably light hair) in northern Europe may come from their near eastern ancestry. Just evolved into something extreme.