Impact of selection and demography on the diffusion of lactase persistence.

The lactase enzyme allows lactose digestion in fresh milk. Its activity strongly decreases after the weaning phase in most humans, but persists at a high frequency in Europe and some nomadic populations. Two hypotheses are usually proposed to explain the particular distribution of the lactase persistence phenotype. The gene-culture coevolution hypothesis supposes a nutritional advantage of lactose digestion in pastoral populations. The calcium assimilation hypothesis suggests that carriers of the lactase persistence allele(s) (LCT*P) are favoured in high-latitude regions, where sunshine is insufficient to allow accurate vitamin-D synthesis. In this work, we test the validity of these two hypotheses on a large worldwide dataset of lactase persistence frequencies by using several complementary approaches. Methodology We first analyse the distribution of lactase persistence in various continents in relation to geographic variation, pastoralism levels, and the genetic patterns observed for other independent polymorphisms. Then we use computer simulations and a large database of archaeological dates for the introduction of domestication to explore the evolution of these frequencies in Europe according to different demographic scenarios and selection intensities. Conclusions Our results show that gene-culture coevolution is a likely hypothesis in Africa as high LCT*P frequencies are preferentially found in pastoral populations. In Europe, we show that population history played an important role in the diffusion of lactase persistence over the continent. Moreover, selection pressure on lactase persistence has been very high in the North-western part of the continent, by contrast to the South-eastern part where genetic drift alone can explain the observed frequencies. This selection pressure increasing with latitude is highly compatible with the calcium assimilation hypothesis while the gene-culture coevolution hypothesis cannot be ruled out if a positively selected lactase gene was carried at the front of the expansion wave during the Neolithic transition in Europe.

Impact of the Financial Crisis on the Performance of European Acquisitions

This study looks at the impact of the recent financial crisis on the short-term performance of European acquisitions. We use institutional theory and transaction cost economic theory to study whether bidders derive lower or higher returns from acquisitions announced after 2008. We investigate shareholders’ stock price reaction to 2245 deals which occurred during 2004–12 across 22 European Union countries. Our results from both univariate and multivariate analysis show that the deals announced in the post-crisis period, corresponding to the period of economic recession, generate higher returns to shareholders as compared to acquisitions announced in the pre-crisis period. We also test the relevance of the Economic and Monetary Union (EMU), that is, the Eurozone, to this value accrual during the recessionary period. We observe that non-EMU transactions obtain significantly higher gains vis-à-vis EMU transactions in the post-crisis years. Overall, announcement returns of European acquisitions have been affected by the financial crisis and the global recession; and companies that target countries with different currency regimes are likely to generate better returns from their acquisitions.