It's from the Kristiansen, Allentoft, Sikora group

See:

Karin Margarita Frei et al
https://journals.plos.org/plosone/ar...l.pone.0219850

"We present results of the largest multidisciplinary human mobility investigation to date of skeletal remains from present-day Denmark encompassing the 3rd and 2nd millennia BC. Through a multi-analytical approach based on 88 individuals from 37 different archaeological localities in which we combine strontium isotope and radiocarbon analyses together with anthropological investigations, we explore whether there are significant changes in human mobility patterns during this period. Overall, our data suggest that mobility of people seems to have been continuous throughout the 3rd and 2nd millennia BC. However, our data also indicate a clear shift in mobility patterns from around 1600 BC onwards, with a larger variation in the geographical origin of the migrants, and potentially including more distant regions. This shift occurred during a transition period at the beginning of the Nordic Bronze Age at a time when society flourished, expanded and experienced an unprecedented economic growth, suggesting that these aspects were closely related."

So, during the metal ages there was movement of people in Denmark, not just movement of goods, i.e raw materials like copper and tin.

"
From 1600 BC onwards, southern Scandinavia became more closely linked to the existing European metal trade networks [4], and from 1500 BC onwards, a period of unparalleled creativity resulted in the formation of a Nordic Bronze Age style, based on stylistic influences from Mycenean and central European workshops [5]. This signaled the beginning of a period of unprecedented burial wealth between 1500–1100 BC when c. 50.000 barrows were constructed in present-day Denmark alone [6]. More than 2000 swords are known from excavated burials, and as they constitute around 10% of the total number of burials, this suggests that a much larger number of swords could have been deposited [7]. There are more Bronze Age swords in present-day Denmark than anywhere else in Europe [8]. During this period, Denmark became Europe’s richest region with respect to number and density of metal depositions [9, 10]. However, this regional development was entirely dependent on the functioning of the long-distance metal trade as revealed by studies on the potential origin of copper [11, 12]. There are no native base metal ores in present-day Denmark. Additionally, recent investigations suggest that wool, too, was traded during the Nordic Bronze Age [13], and that a number of glass beads found as grave goods came from as far away as Mesopotamia and Egypt [14]."

"
Some of these studies suggested a pattern in which exogamy may have prevailed during the Corded Ware and Bell Beaker/Early Bronze Age societies, as a majority of the women investigated were of non-local origin [3, 50]. In other cases, like in the multi-isotopic investigations of skeletal remains of 264 individuals from the British Chalcolithic–Early Bronze Age, results indicated a high degree of mobility but with “little difference between male and female migration histories across Britain” [51].Another study based on investigations of the human remains (mostly of young males) excavated from the Bronze Age battlefield of Tollense (c. 1250 BC) in northern Germany, revealed that a large majority of these individuals were of non-local origin, and that they potentially originated from various places characterized by different geologies [47]. A somewhat similar case to the Tollense study may be found in the unusual Late Bronze Age cemetery of Neckarsulm in south-western Germany where only males were buried. The strontium isotope analyses conducted on individuals from this site revealed that one third of these individuals were also of non-local origin [53].
Yet another recent study from southern Sweden, based on multi-isotopic analyses of 61 individuals dating from 2300–1200 BC, suggested that mobility was rather high in this region too, but no differences with respect to social status or sex of individuals investigated could be seen [49]."

"With respect to ancient DNA characterization, only a few individuals from present-day Denmark from this period have been analyzed thus far [1]. Our strontium isotope analyses encompass five of these individuals, and their overall genomic information resembles the typical Corded Ware-like gene pool, typical for northern and central Europe at this time [1]. More specifically, they all have the genomic "steppe signature" that ultimately derives from the Yamnaya-culture-related people who expanded into central and northern Europe shortly after 3000 BC [1, 2]. The Corded Ware and related cultures somehow emerged from this admixture between Yamnaya-related and the Late Neolithic population and started expanding across large parts of Central and Northern Europe. This seems to imply that the population we investigate in this study might represent a newly genetically transformed population."

"Our results indicate a change from around 1600 BC onwards, as individuals with Sr isotopic values above 0.713 start to appear in our dataset and suggest mobility. Furthermore, the large range of values (between 87Sr/86Sr = 0.713 to 0.718) represented by these individuals imply that the areas which the non-locals individuals migrated from were geographically diverse and might have included more distant regions.

The shift in human mobility characterized by the expansion in diversity of areas of origin of the non-locals appears to occur parallel to the emergence of the long-distance metal trade that connected present-day Denmark to areas in, e.g., central and southern Europe as well as the British Isles e.g. [4, 5, 12]. Moreover, it appears that mobility is most evident within the group of individuals buried in barrows, compared to those in flat graves (all the nine Early Bronze Age flat graves herein investigated suggest “local” origin) (Table 2). This differs from the recent results from Scania in southern Sweden which do not seem to show differences with regards to mobility and social status [49]. This aspect attests to potential differences within the Nordic Bronze Age region."

A previous study appears to indicate that this mobility pattern, including the expansion trend with respect to the diversity of areas, continued into the Late Bronze Age (1100–500 BC) [18] as well (Fig 6). "

So, the admixture was among the elite.

"When comparing our study with other recent similar investigations within the 2nd millennium in Europe, a quite complex picture emerges what seems to include different mobility patterns depending on the areas. While in southern Sweden tooth enamel strontium isotope analyses revealed that both males and females of varying socio-economic status and wealth migrated to the area during the Nordic Bronze Age [49], other investigations in, e.g. the Lech Valley area in southern Germany, point to a high degree female mobility [48]. Yet another recent study from Northern Italy also reports mobility mostly of women in which appears to have been a patrilocal society [37].

In sum, our study provides new insights into mobility during a crucial point in time at the beginning of the Nordic Bronze Age. This mobility might have caused a rapid homogenization of gene pools. While it will be desirable and very relevant to discuss the genetic results more in detail with the herein presented strontium isotope results and their potential implications for Europe-wide population dynamics and mobility from particularly the “steppe” people, we consider that with only the few samples at hand (five) it would be too premature to expand on this issue at this stage. "