The increased aging of the population is a consideration, but increased risk factors across all age groups limit aging as a sole explanation [ 3].
It should be mentioned, though, that caution should be taken when considering sexual selection as a sole explanation for the positive selection here found, because fru also codes for non-sex-specific transcripts [ 12], so it is possible that the signal of adaptive selection may be the result of selection over phenotypes not related to sexual behavior.
It is expected that the Nearctic-distributed copperhead lineage suffered small effective population sizes due to bottlenecks during glacial cycles (Guiher and Burbrink 2008), and the likelihood of large and stable effective populations in tropical lineages such as the python also contraindicates a primary role for population size differences as a sole explanation.
Neither habitat change, competition for resources or exposure to predation provided a consistent sole explanation for the drastic population crashes shown by five smaller ungulate species (body mass 10 45 kg).
In this study, we find that the frequency of the derived allele is low in the PWC (5%) compared to the frequency in the extant Swedish population, and that the change in frequency is incompatible with genetic drift as the sole explanation under a model of population continuity.
However, Bogart and Lehman (1973) argue that advertising can never be the sole explanation of why a brand is at the forefront of a customer's mind.
Because the association with M. pneumoniae is not fully understood, clinicians should be cautioned against accepting M. pneumoniae as the sole explanation for an encephalitic illness, especially if this diagnosis is based on a single IgM test.
Nevertheless, the elastase-anti-elastase hypothesis, while popular for a time, is no longer considered the sole explanation for the pathogenesis of emphysema, in the same way that neutrophils are no longer believed to represent the only cellular source of elastolytic enzymes in the lung [ 47].
Improved registration is likely to have played a certain role, but it cannot be the sole explanation for this finding.
Although this may explain part of the earlier age of diagnosis, as H. pylori is considered a class 1 carcinogen, it cannot be the sole explanation, as some populations in which H. pylori is prevalent have high incidences of gastric cancer, while other highly infected populations do not (Singh and Ghoshal, 2006; Yamaoka et al, 2008).
The fact that key sources of sugar energy are low in energy from fat (e.g., soft drinks, table sugar) and that many sources of fat are low in sugar (e.g., oils, butter, and fat-spreads, cheese, meat products) undoubtedly contributes to the inverse relationship between sugar and fat such that a mathematical effect is unlikely to be the sole explanation.
