By reading single-letter DNA differences in the genomes of thousands of Europeans, researchers can tell a Finn from a Dane and a German from a Brit. In fact a visual genetic map mirrors the geopolitical map of the continent, right down to Italy's boot.
"It tells us that geography matters," says John Novembre, a population geneticist at the University of California, Los Angeles, who led one of the studies. Despite language, immigration and intermarriage, genetic differences between Europeans are almost entirely related to where they were born.
This, however, does not mean that the citizens of each European nation represent miniature races. "The genetic diversity in Europe is very low. There isn't really much," says Manfred Kayser, a geneticist at Erasmus University Rotterdam in the Netherlands, who led the other study.
The question of how genetic diversity in Europe relates to national borders is an empirical one. Finns probably constitute a local "race" or subrace (or two) distinict from other Europeans, while -- at the national level -- the Swiss apparently do not.
But I strongly take issue with the suggestion that "low" levels of genetic diversity are of no taxonomic significance. The paper under discussion (and many before it) pretty clearly demonstrate the opposite. One can imagine plenty of forensic, genealogical, preservationist, and other applications which may benefit from knowledge of these "small" genetic differences (and those which remain to be discovered). Precisely how one chooses to (sub-)classify Europeans will depend on one's objectives and the available statistical tools and data, but the existence of substructure is not in question. Choosing to call the resulting sub-European taxonomic units "miniature races", "subraces", "local types", or so on, is merely a matter of semantics.
Some relevant discussion of the race concept, from Anthropology A to Z :
But race is, from the biological point of view, not a static, but a dynamic condition. Within the constantly changing movement of "life" it represents a breeding unit continously modifying itself, by infinitesimal degrees, through mtuations. This mobile condition was most aptly formulated by the American geneticist Dobzhansky, who said: "Race is a process." His statement at last fits the concept of race meaningfully into the history of life, and at the same time makes race understandable as the smallest ever-changing taxonomic unit (genetic population) by which we can interpret the total course of organic evolution.
To identify a race, it is theoretically sufficient to note the prevalence of a new gene and the consequent characteristic trait or traits that occur predominantly in a particular genetic population and distinguish it from neighboring populatins. But the one-trait basis of differentiation, considering the vast numbers of genes in mammals alone, would lead to an unjustifiable multiplicity of taxonomic units such as species and subspecies. Therefore, Fischer's early postulate -- of the gene groups in man which unite to produce certain characteristic patterns of traits, thus permitting a clear differentation of the various genetic poulations of a species within a large framework -- has been used as a basis for the determination and classification of races. [. . .]
There is some disagreement concerning the numbers of races, even though the races are always differentiated in accordance with the same basic principles of genetics. The differences in the estimated numbers result mostly from differences in emphasis. Some writers tend to base their estimate on the number of observable regional genetic populations; others are concerned with more general considerations. Of course, the more local races that are subsumed under related super-regional entities, or "major races" (i.e., Caucasoid, Mongoloid, Congoid), the smaller the number of single traits withing each characteristic combination that can be taken into consideration. [n/a: Conversely, as we become technically able to measure very large numbers of traits (e.g., hundreds of thousands of SNPs using gene chips), we can refine classifications.] At at the same time, authors will differ in assigning local groups to one of the other major race, especially in the contact zones. These differences in taxonomy and in point of view do not militate, however, against the validity of the definition of race itself; they arise solely from the fact that various writers evaluate racial traits differently and assign a different significance to them. Such conceptual differences also underline the fact that in talk about races we are dealing with developing life, with processes not easily subsumed under the necessarily rigid schemes which our need for methodical classification demands.
A race is a group of individuals who belong to the same reproductive community, and are characterized by the possession of certain genes that differ from those corresponding populations of the same species. The original gene pool of a population is steadily, but very slowly, enriched through mutations, of which only a limited number will survive selection pressures over the long term. For the accumulation of favorable (partially new) genes within a population to an extent that might become characteristic, restriction of propagative activity for a certain time is necessary, so that the gene flow between it and neighboring genetic populations is stopped. This process is called isolation. Its result depends largely on the duration and the severity of the mating restrictions -- how long the gene flow in and out of the propagation circle is actually stoppped. This leads us to a prerequisite for the formation of a race. It is not possible for several new races to develop sympatrically -- that is, from the same original population and simultaneously in the same geographic space. The formation of a race can occur only allopatrically -- that is, in separate living areas, or isolates. The original population, just before splitting into daughter populations which in turn become isolated, was essentially uniform in the racial sense, and the daughter populations have come out of the same gene pool. Differentiation starts with the actual isolation. If differentiation continues for a certain span of time and a corresponding number of generations, the phylogenetic direction is established.
The isolation of populations is normally due to geographic barriers -- seas, deserts, dry prairies, obstructive forests or tropical-rain-forest zones, edge locations (peninsulas or continental tips).
Thus the foundations were laid for what seems almost self-evident to us today; namely, that races are groups of individuals with similar gene compositions, which were built from mutant alleles that combined in various ways and became differentiated in their geographic regions, but which may be disintegrated in the process of cross-breeding. Difference in race does not constitute a barrier to the production of offspring. It became possible to make the process of race formation increasingly understandable in terms of cause and effect. Genes go through mutation; then, through the mechanism of natural selection, they are either increased in frequency, becoming part of combinations in characteristic concentrations, or else they fail to perpetuate themselves.
 Heberer, Gerhard, Carleton S. Coon, Edward E. Hunt, Gottfried Kurth, and Ilse Schwidetzky-Roesing. 1963. Anthropology A to Z: Based on the work of Gerhard Heberer, Gottfried Kurth, and Ilse Schwidetzky-Roesing. New York: Grosset & Dunlap.