We discuss (i) the measurement, (ii) interpretation and (iii) technical impact of temperature-dependent wall slip and its activation energy for polar and non-polar hydrocarbon Newtonian fluids moving relative to machined metal surfaces. A newly developed apparatus, the slip length tribometer (SLT), overcomes the drawbacks of existing measurement devices in terms of characterising relevant rough surfaces by measuring the slip length at different temperatures over a sufficiently large wetted area. The experimental data show that the bulk viscosity and slip length at the fluid–metal interface is independent of the shear rate up to $10^5\,\mathrm {s}^{-1}$, being consistent with recent results from molecular dynamics simulations by Mehrnia & Pelz (J. Mol. Liq., vol. 336, 2021, 116589). Furthermore, the activation energies for wall slip and bulk shear determined by means of the SLT differ by a factor of two, i.e. $E_{\lambda }\approx 0.5 E_\mu$ for non-polar hydrocarbon molecules sliding relative to metal walls. This difference is explained by a generalised Eyring model applied to wall slip. The paper closes with the impact of wall slip on Sommerfeld's similarity theory of tribology and the resulting Stribeck curve (Sommerfeld, Z. Math. Phys., vol. 50, 1904, pp. 97–155; Z. Tech. Phys., vol. 2. Jahrg., 1921; Mechanik der deformierbaren Medien, 1944, Akademische Verlagsgesellschaft Becker & Erler). For this purpose, Reynolds’ equation generalised for wall slip is solved in combination with the experimentally determined constitutive relations for bulk shear and wall slip to predict typical characteristics of journal bearings. The results show that, for a typical journal bearing, where the ratio of slip length to average bearing clearance is of the order of $10^{-2}$, the influence of wall slip on both load-carrying capacity and dissipation is not negligible. This work combines nanofluidics and tribology in order to provide methods and knowledge for e.g. tailor-made fluids and interfaces.

Traditionally, it is understood that dizygotic (DZ) twins always have a dichorionic placenta. However, with 8% blood chimerism in DZ twins, placental sharing is probably more common than previously has been recognized. In this article, we will review all available cases of monochorionic dizygotic (MCDZ) twins. A total of 31 twins have been described in literature. A monochorionic diamniotic placenta is reported in all cases. Assisted reproductive technology is responsible for the origin of the pregnancy in 82.1% of the cases. In 15.4% of the sex-discordant twins, a genital anomaly was reported in one of the twins. Chimerism is demonstrable in 90.3% of the twins, leading to various diagnostic difficulties. As this review shows that most MCDZ twins are discovered by accident, it can be argued that it is far more common than has been assumed until now. However, the prevalence is still unclear. Awareness of MCDZ twinning is important, with subsequently correct medical strategies. Similarly, the resulting (blood) chimerism is essential to consider in diagnostic procedures, pre- and postnatally. More research on the effect of placental transfusion between sex-discordant twins is required.

I think it is fair to say that synergy is an idea whose time has finally come. It seems that every week another new example of synergy is reported in some scientific journal, and articles about synergy are nowadays routinely accepted for publication in various disciplines. This was certainly not the case 30 years ago. Back then using the term “synergy” in a journal submission was an almost certain kiss of death. I speak from personal experience. So times have changed. However, the theory proposed in my 1983 book, The Synergism Hypothesis: A Theory of Progressive Evolution^ has had a more complex journey, and herein lies a bit of intellectual history and some lessons about the culture and politics of science.

Although I will respond to each commentator separately, some of my responses will be applicable more generally.

Holistic Darwinism is a candidate name for a major paradigm shift that is currently underway in evolutionary biology and related disciplines. Important developments include (1) a growing appreciation for the fact that evolution is a multilevel process, from genes to ecosystems, and that interdependent coevolution is a ubiquitous phenomenon in nature; (2) a revitalization of group selection theory, which was banned (prematurely) from evolutionary biology over 30 years ago (groups may in fact be important evolutionary units); (3) a growing respect for the fact that the genome is not a “bean bag” (in biologist Ernst Mayr's caricature), much less a gladiatorial arena for competing selfish genes, but a complex, interdependent, cooperating system; (4) an increased recognition that symbiosis is an important phenomenon in nature and that symbiogenesis is a major source of innovation in evolution; (5) an array of new, more advanced game theory models, which support the growing evidence that cooperation is commonplace in nature and not a rare exception; (6) new research and theoretical work that stresses the role of nurture in evolution, including developmental processes, phenotypic plasticity, social information transfer (culture), and especially the role of behavioral innovations as pacemakers of evolutionary change (e.g., niche construction theory, which is concerned with the active role of organisms in shaping the evolutionary process, and gene-culture coevolution theory, which relates especially to the dynamics of human evolution); (7) and, not least, a broad effort to account for the evolution of biological complexity — from major transition theory to the “Synergism Hypothesis.” Here I will briefly review these developments and will present a case for the proposition that this paradigm shift has profound implications for the social sciences, including specifically political theory, economic theory, and political science as a discipline. Interdependent superorganisms, it turns out, have played a major role in evolution — from eukaryotes to complex human societies.

The response by Somit and Peterson to my earlier commentary in this journal (Corning, 2000), which sharply criticized their little-noticed 1997 book (by their own admission), must seem like old news that should be relegated to the obituary pages. On the contrary, it concerns one of the central political issues of our time—what sustains modern democracy, and what are its future prospects. Somit and Peterson in their modest book offered both a diagnosis and a prescription. I concluded in my essay that the result was disappointing—more for what was omitted than for any commissions. My critique involved a rather subtle argument, and, judging by the authors' response (Somit and Peterson, 2001), it seems to have been lost on them as well.

With the support of a grant from the Harry Frank Guggenheim Foundation, research is currently underway on a major effort to rethink the basic theoretical issue that inspired the emergence of sociobiology. That issue, in a nutshell, concerns the explanation for the origins and evolution of social life (human societies being only one example among many others).

In the famous (some would say infamous) final chapter of his discipline-defining volume, Sociobiology: The New Synthesis, biologist Edward O. Wilson invited us to consider humankind as if we were zoologists from another planet. In this light, Wilson said, “the humanities and social sciences shrink to specialized branches of biology” (1975:547). One of the functions of the new discipline of sociobiology, Wilson suggested, was “to reformulate the foundations of the social sciences…” (1975:4). Wilson cautioned, however, that it “remains to be seen” whether or not the social sciences can be “truly biologized” in this fashion.

An evolutionary perspective, which is currently enjoying a revival in the social sciences, raises the possibility of a major transformation in the study of political development and modernization. It may be desirable to supplement (and in some instances replace) the concept of “political development” with the concept of “political evolution.” Political development may be likened to the biological process of ontogeny. It involves the construction of a viable set of political qua cybernetic processes and structures at any level of social organization, from wolf packs to human families to empires. Political evolution is an aspect of phylogeny. It involves the invention, elaboration, and diffusion of novel political forms of all kinds, only some of which may be more effective, or inclusive, or democratic, etc. Nor are all evolutionary changes necessarily “better” (i.e., more adaptive). Political development is concerned with problems of social engineering, while political evolution is concerned with architectonics—with the emergence of functionally significant political innovations. Political development is always situation-specific, while political evolution is also historical and may include changes that diffuse and become “species-wide.” Political evolution is thus a dimension of the larger process of biological evolution. The emergence of political systems, which long predates the evolution of humankind, constitutes a set of adaptive strategies with significant evolutionary consequences. Political development and political evolution may go hand in hand, but this is not always the case. A particular polity may develop or decay independently of the larger process of political evolution. Among the many theoretical implications of this conceptual reformulation, we briefly address the impact on functionalist theory, modernization theory, social mobilization theory, political economy (positive theory), world systems theory, dependency theory, and contemporary Marxist views.

The accumulating scientific evidence — across many disciplines — regarding human evolution and the dualities and complexities of human nature indicates that the core ideological assumptions of both capitalism and socialism are simplistic and ultimately irreconcilable. A biologically grounded approach to social justice enables us to articulate a new ideological paradigm that I call “Fair Shares.” This paradigm consists of three complementary normative principles. First, goods and services should be distributed to each according to his or her basic needs. Second, surpluses beyond the provisioning of our basic needs should be distributed according to merit. And, third, each of us is obliged in return to contribute to the “collective survival enterprise” in accordance with his or her ability. Though none of these three principles is new, in combination they provide a biologically informed middle way between capitalism and socialism. Some of the many issues that are raised by this formulation are also briefly addressed.

Evolutionary ethics is a subject that has been debated ever since Darwin's day. The basic issue, in a nutshell, is whether or not human ethical systems can be explained — and justified — in terms of evolutionary principles. In recent years there has been an upsurge of publications devoted to this issue, including many new books (as well as a number of books on Darwinism and religion) and countless journal articles. Indeed, an Internet search using the term “evolutionary ethics” yielded 65,400 citations of various kinds. As this outpouring of publications suggests, there has been a great diversity of views on the subject over the years.