Whenever I am back in Denmark I eat copious amounts of tebirkes. Tebirkes is a Danish pastry quite unlike anything else (recipe). Closest living relative that most people know would probably be the croissant, but they are definitely different species.
The vacation in Big Sur and San Francisco that I have just returned from took us by Solvang, CA. It's a quaint village in Santa Barbara County settled in 1911 by Danes, and it now serves as a tourist attraction. Most things there, however, aren't very Danish anymore. The bakeries, however, still make quite decent bread and pastries. I'm somewhat of a connoisseur. More of a gourmand than a gourmet, I suppose.
So I had a tebirkes at Mortensen's Bakery, and I have to tell you straight away that it wasn't the big thrill I had hoped for. It was too bready, rather than crunchy like good pastry is supposed to be (you can tell American bakers, but it won't make any difference - a 'danish' here is looks like the real thing, but the bread-part is more like a bun than the laminated dough it should be). On top of that, it was topped off not by poppy seeds, but by sesame seeds. Weird. I was hungry (that's normal), so it went down, and it wasn't really bad. In fact it was great, because it made me think about the evolution of tebirkes.
Consider that when a small population of tebirkes moved from Denmark to California, there was essentially a founder effect (small part of a larger population emigrates), which then carries with it only part of the variation of the original population. The tebirkes that founded the California population in Solvang probably already differed somewhat phenotypically from the mean Danish population. However, that is unlikely to explain the breadyness and the sesame seeds. I suspect that this is due in part to gene flow between related native California breads, which are more bread-like than pastry-like, and in part due to mutations. At one point a mutation from poppy to sesame occurred, and was lucky enough to get fixed in the population, either by natural selection or genetic drift. Since the founding population is likely to have been rather small, both selection and drift are likely contributors to the fixation of sesame. I hypothesize that when this occurred early in the tebirkes settlement of Solvang, a native bread-tebirkes hybrid, which probably had lower fitness due to outbreeding depression, had the highly favorable poppy-to-sesame mutation, which outweighed the disadvantage of the breadyness.
A more in-depth survey of the Solvang tebirkes would be imperative to assess the validity of the bread-pastry hybrid sesame mutation hypothesis. It is my intention to secure funds for a three-day weekend in the near future.
Lastly, notice that while I have deep knowledge of the original Danish tebirkes population, a systematic study might reveal that the natural history of the Danish population isn't as simple as one might expect. At the moment there are definitely two sub-types of tebirkes: the non sweet and the semi sweet (i.e. without and with remonce, respectively). It is possible that the Solvang tebirkes descends from the non sweet type, and that the remonce is a later occurrence - either by mutation or, more likely, by hybridization with other pastry species that have the remonce phenotype. Statistical methods for elucidating the natural history of the original Danish tebirkes would include a biogeographic analysis of the current population. Additionally, in recent years the Danish tebirkes population has seen a shift in morphology. There are reports of subpopulations that vary considerably in size, and, more importantly, in consistency and flavor. My suspicion is that this is a separate immigration of breads from other parts of Europe and the Middle East, which we have seen an influx of in recent years. However, due to the closeness to the original tebirkes, my hunch is that this is caused by horizontal gene transfer from breads such as the pita and the baklava. Alternatively, it could be caused by hybridization with the frøsnapper, another pastry of more recent origin, but with similar texture and abundant poppy seeds (though these are always the dark type, while Danish tebirkes can be with either light (picture) or dark poppy seeds).
It is my hope that an investigation into the natural history of the tebirkes, both in the Solvang and Denmark populations, will contribute both to our understanding of the dynamics of pastry-speciation, as well as to the conservation of the rich diversity of these unique pastries.