Ancient DNA studies based solely on low resolution mtDNA sequences aren't exactly cutting edge science nowadays, but this one is still interesting and somewhat surprising in that it describes an unusually Near Eastern-like population from post-Neolithic Iberia. These people were probably either fresh off the boat colonists from the Near East, or, alternatively, the descendants of Neolithic farmers from the Near East who were yet to begin mixing with other distinct populations to produce the modern Iberian mtDNA gene pool. The authors of this paper favor the second scenario:
Abstract: Previous mitochondrial DNA analyses on ancient European remains have suggested that the current distribution of haplogroup H was modeled by the expansion of the Bell Beaker culture (ca 4,500–4,050 years BP) out of Iberia during the Chalcolithic period. However, little is known on the genetic composition of contemporaneous Iberian populations that do not carry the archaeological tool kit defining this culture. Here we have retrieved mitochondrial DNA (mtDNA) sequences from 19 individuals from a Chalcolithic sample from El Mirador cave in Spain, dated to 4,760–4,200 years BP and we have analyzed the haplogroup composition in the context of modern and ancient populations. Regarding extant African, Asian and European populations, El Mirador shows affinities with Near Eastern groups. In different analyses with other ancient samples, El Mirador clusters with Middle and Late Neolithic populations from Germany, belonging to the Rössen, the Salzmünde and the Baalberge archaeological cultures but not with contemporaneous Bell Beakers. Our analyses support the existence of a common genetic signal between Western and Central Europe during the Middle and Late Neolithic and points to a heterogeneous genetic landscape among Chalcolithic groups.
Of course, these results don't debunk in any way the generally accepted theory that the enigmatic Bell Beakers first expanded from what is now Portugal. Indeed, a Principal Component Analysis (PCA) from the paper shows Bell Beaker mtDNA from Germany (BBC) right next to mtDNA from late Neolithic Portugal (NPO). On the other hand, the El Mirador cave sample (MIR) appears most similar to mtDNA from Germany belonging to the middle Neolithic Salzmunde culture (SMC).
Gómez-Sánchez D, Olalde I, Pierini F, Matas-Lalueza L, Gigli E, et al. (2014) Mitochondrial DNA from El Mirador Cave (Atapuerca, Spain) Reveals the Heterogeneity of Chalcolithic Populations. PLoS ONE 9(8): e105105. doi:10.1371/journal.pone.0105105