The evolutionary biology of sex

In 1861, Charles Darwin wrote "We do not even in the least know the final cause of sexuality; why new beings should be produced by the union of the two sexual elements, instead of by a process of parthenogenesis". It was hardly possible to begin to answer this question at that time, in view of the contemporary lack of knowledge of genetics and cell biology. Since then, research into the cellular basis of reproduction has shown that sexual reproduction is the norm for the majority of eukaryotes, with huge consequences for their biology. The evolution of sex and some of its consequences are the subject of the series of reviews, and a Primer, in this special issue of Current Biology.     

The evolutionary biology of child health

I apply evolutionary perspectives and conceptual tools to analyse central issues underlying child health, with emphases on the roles of human-specific adaptations and genomic conflicts in physical growth and development. Evidence from comparative primatology, anthropology, physiology and human disorders indicates that child health risks have evolved in the context of evolutionary changes, along the human lineage, affecting the timing, growth-differentiation phenotypes and adaptive significance of prenatal stages, infancy, childhood, juvenility and adolescence. The most striking evolutionary changes in humans are earlier weaning and prolonged subsequent pre-adult stages, which have structured and potentiated maladaptations related to growth and development. Data from human genetic and epigenetic studies, and mouse models, indicate that growth, development and behaviour during pre-adult stages are mediated to a notable degree by effects from genomic conflicts and imprinted genes. The incidence of cancer, the primary cause of non-infectious childhood mortality, mirrors child growth rates from birth to adolescence, with paediatric cancer development impacted by imprinted genes that control aspects of growth. Understanding the adaptive significance of child growth and development phenotypes, in the context of human-evolutionary changes and genomic conflicts, provides novel insights into the causes of disease in childhood.     

The morphogenesis of evolutionary developmental biology

The early studies of evolutionary developmental biology (Evo-Devo) come from several sources. Tributaries flowing into Evo-Devo came from such disciplines as embryology, developmental genetics, evolutionary biology, ecology, paleontology, systematics, medical embryology and mathematical modeling. This essay will trace one of the major pathways, that from evolutionary embryology to Evo-Devo and it will show the interactions of this pathway with two other sources of Evo-Devo: ecological developmental biology and medical developmental biology. Together, these three fields are forming a more inclusive evolutionary developmental biology that is revitalizing and providing answers to old and important questions involving the formation of biodiversity on Earth. The phenotype of Evo-Devo is limited by internal constraints on what could be known given the methods and equipment of the time and it has been framed by external factors that include both academic and global politics.     

The evolutionary biology of insect hearing

Few areas of science have experienced such a blending of laboratory and field perspectives as the study of hearing. The disciplines of sensory ecology and neuroethology interpret the morphology and physiology of ears in the adaptive context in which this sense organ functions. Insects, with their enormous diversity, are valuable candidates for the study of how tympanal ears have evolved and how they operate today in different habitats.     

Iconometrographics in evolutionary biology

The essential dialogue between Apollinian and Dionysiac poles required for the advance of music and art was likened to the scientific debate between «justifiers» and «innovators». The use of ratios and simple algorithms was indicted as being retrogressive in terms of modern microcomputer technology and iconometrographic models. Three examples were used to illustrate the approach in the resolution of complex data sets comparing samples: (1) 45,XO with a 46,XY controls, (2) sexual dimorphism in young adults and (3) Black and White Olympic athletes. The iconometrographic approach was proposed as a primary orientation in human biology, particularly in secular trend studies concerned with the recognition and assessment of complex evolutionary trends.     

The evolutionary biology of sterile soldiers in aphids

The discovery of a sterile soldier caste in aphids by Shigeyuki Aoki offered behavioural ecologists new and interesting subjects for the study of insect sociality. Quantitative studies on the behaviour of soldiers and the population and genetic consequences are, however, scant. This review summarizes the distribution and peculiarities of sterile soldiers in different aphid taxa and also reports on phenomena that may relate to the evolution of aphid soldiers.     

The tragedy of the commons in evolutionary biology

Garrett Hardin's tragedy of the commons is an analogy that shows how individuals driven by self-interest can end up destroying the resource upon which they all depend. The proposed solutions for humans rely on highly advanced skills such as negotiation, which raises the question of how non-human organisms manage to resolve similar tragedies. In recent years, this question has promoted evolutionary biologists to apply the tragedy of the commons to a wide range of biological systems. Here, we provide tools to categorize different types of tragedy and review different mechanisms, including kinship, policing and diminishing returns that can resolve conflicts that could otherwise end in tragedy. A central open question, however, is how often biological systems are able to resolve these scenarios rather than drive themselves extinct through individual-level selection favouring self-interested behaviours.     

The meaning of categorical ranks in evolutionary biology

Despite having been utilized for over 250 years, Linnaean ranks are periodically dismissed by some systematists and evolutionary biologists. Here, we discuss recent criticisms and point out that they are often the result of a misunderstanding of both the meaning and the intent of such ranks. Although arbitrary in some cases, ranks contain meaningful taxonomic information, facilitate communication, and serve as proxies for a fully resolved and correctly dated tree of life. Ranks favor communication and evolutionary comparisons, but they do not make assumptions about equal age or diversity for any two taxa with the same Linnaean category.     

The second wave of evolutionary economics in biology

Several core issues in economics and biology overlap substantially. At the theoretical level, these include analogies and differences among rational choice, learning, genetic evolution and cultural evolution. At the empirical level, they include the structure of decision making, its neural basis and, more generally, human nature. We illustrate here the increasingly important collaboration between economics and biology with several characteristic examples, including signaling, markets, statistical reasoning, cooperation, punishment, reputation and social norms. In contrast to the mutual borrowing of ideas during the 1970s and 1980s, we now see the joint exploration of empirical and theoretical issues by biologists and economists that constitutes a second wave of interactions between the two disciplines.     

Methodological problems in evolutionary biology VI. The force of evolutionary epistemology

Evolutionary epistemology takes various forms. As a philosophical discipline, it may use analogies by borrowing concepts from evolutionary biology to establish new foundations. This is not a very successful enterprise because the analogies involved are so weak that they hardly have explanatory force. It may also veil itself with the garbs of biology. Proponents of this strategy have only produced irrelevant theories by transforming epistemology's concepts beyond recognition. Sensible theories about knowledge and biology should presuppose that various long-standing problems concerning relations between the mental and the physical are solved. Such problems are wrongly disregarded by evolutionary epistemologists.     

The psychologic effects of spontaneous abortion.

Although 14% to 18% of pregnancies end in spontaneous abortion, miscarriage is often not recognized as a significant occurrence. Women may experience grief reactions similar to those after the loss of a neonate. If the woman is not given an opportunity to deal with her grief, there may be continuing feelings of sadness, inadequacy and fearfulness as well as impairment in the relationships with her spouse and children. Methods of helping the couple during this time include acknowledging the significance of the loss, providing information, permitting the couple to see the fetus, if desired, and suggesting a memorial service. Some women may require individual or group therapy to deal with their feelings.     

The proper place of hopeful monsters in evolutionary biology

Hopeful monsters are organisms with a profound mutant phenotype that have the potential to establish a new evolutionary lineage. The Synthetic Theory of evolutionary biology has rejected the evolutionary relevance of hopeful monsters, but could not fully explain the mechanism and mode of macroevolution. On the other hand, several lines of evidence suggest that hopeful monsters played an important role during the origin of key innovations and novel body plans by saltational rather than gradual evolution. Homeotic mutants are identified as an especially promising class of hopeful monsters. Examples for animal and plant lineages that may have originated as hopeful monsters are given. Nevertheless, a brief review of the history of the concept of hopeful monsters reveals that it needs refinements and empirical tests if it is to be a useful addition to evolutionary biology. While evolutionary biology is traditionally zoocentric, hopeful monsters might be more relevant for plant than for animal evolution. Even though during recent years developmental genetics has provided detailed knowledge about how hopeful monsters can originate in the first place, we know almost nothing about their performance in natural populations and thus the ultimate difference between hopeful and hopeless. Studying the fitness of candidate hopeful monsters (suitable mutants with profound phenotype) in natural habitats thus remains a considerable challenge for the future.     

Explanatory pluralism in evolutionary biology

The ontological dependence of one domain on another is compatible with the explanatory autonomy of the less basic domain. That autonomy results from the fact that the relationship between two domains can be very complex. In this paper I distinguish two different types of complexity, two ways the relationship between domains can fail to be transparent, both of which are relevant to evolutionary biology. Sometimes high level explanations preserve a certain type of causal or counterfactual information which would be lost at the lower level; I argue that this is central to the proper understanding of the adaptationist program. Sometimes high level kinds are multiply realised by lower level kinds: I argue that this is central to the understanding of macroevolution.