Biomedical and social scientists are increasingly calling the biological sex into question, arguing that sex is a graded spectrum rather than a binary trait. Leading science journals have been adopting this relativist view, thereby opposing fundamental biological facts. While we fully endorse efforts to create a more inclusive environment for gender‐diverse people, this does not require denying biological sex. On the contrary, the rejection of biological sex seems to be based on a lack of knowledge about evolution and it champions (...) species chauvinism, inasmuch as it imposes human identity notions on millions of other species. We argue that the biological definition of the sexes remains central to recognising the diversity of life. Humans with their unique combination of biological sex and gender are different from non‐human animals and plants in this respect. Denying the concept of biological sex, for whatever cause, ultimately erodes scientific progress and may open the flood gates to “alternative truths.”. (shrink)

Phylogenetically controlled studies across multiple species correct for taxonomic confounds in physiological performance traits. Therefore, they are preferred over comparisons of two or few closely‐related species. Funding bodies, referees and journal editors nowadays often even reject to consider detailed comparisons of two or few closely related species. Here, we plea for a less dogmatic stance on such comparisons, because phylogenetic studies come with their own limitations similar in magnitude as those of two‐species comparisons. Two‐species comparisons are particularly relevant and instructive (...) for understanding physiological pathways and de novo mutations in three contexts: in a purely mechanistic context, when differences in the regulation of a trait are the focus of investigation, when a physiological trait lacks a direct connection to fitness, and when physiological measures cannot easily be standardized among laboratories. In conclusion, phylogenetic comparative and two‐species studies have different strengths and weaknesses and combining these complementary approaches will help integrating biology. (shrink)