The paper on topic "Population Genomics of Stone Age Eurasia" states: "The introduction of farming reached a 1,000-year standstill at the doorstep to Southern Scandinavia before finally progressing into Denmark around 6 ka [thousands of years ago]. It is not known what caused this delay,"
The authors forgot that this neolithization delay was even greater in the rest of the European coast, with exceptions increasing towards the south (a small enclave in the south of Great Britain > central coast of France > the southern half of the Portuguese coast > most of the Mediterranean coast).
Only fish have significant percentages of vitamin D, eggs and beef liver still have something, but other foods have very little. The diet of the first farmers was very deficient in vitamin D, causing problems such as rickets. In the south, under the sun's action, the skin produces vitamin D and compensates for this deficiency, but as we move north, solar radiation decreases and as temperatures also drop, we expose the skin less and less to the sun.