Death in Venice: the homosexuality enigma.

A hypothesis is presented which regards homosexuality neither as an aberration of 'normal' human sexuality, i.e. heterosexuality, nor as a 'defect', genetically transmitted from parent(s) to offspring. Nor is homosexuality regarded as the regrettable result of accidental circumstances. Homosexuality, it is maintained, is simply inherent in the human reproductive strategy; an option which evolved during the millions of years of human evolution as a solution for problems inherent in a polygynic, yet social species living in relatively small groups: homosexuality diminishes intra-male competition on the 'reproductive market'. This enables males to work closely together in all fields of society (hunting, war etc), rather than competing with each other for access to females. Homosexuality thus largely contributes to group stability. However, because our present-day situation differs vastly from the situation in which the human reproductive strategy evolved, the phenomenon hardly plays a role any more in the maintainance of the fitness and the stability of the population as a whole. Instead, due to 'cultural', often religious prejudices, homosexuals nowadays are treated as belonging to an 'out-group', and discriminated against accordingly.

Deceive, and be deceived!

In their struggle for life, many species, for example prokaryotes, plants and animals, defend themselves by producing substances which may poison or disorientate (potential) enemies (grazers/predators etc), or signal information which puts (potential) enemies on the wrong track. Examples of poisonous/ disorientating substances include prussic acid (e.g. almonds) or morphine (papaver), examples of 'false' visual cues include the appearance of harmless hoverflies which strongly resemble 'dangerous' wasps or certain orchid flowers which resemble the female sex organs of certain insects ('mimicry'). Misleading is an essential part of communication systems.

Cancer: a reproductive strategy of "ultra-selfish" genes?

A hypothesis is presented in which the process of "malignant transformation" which ultimately results in the rapidly dividing tumor(s)(cells) causing "cancer", is regarded as an evolved reproductive strategy of "ultra-selfish" (proto-)(onco-) genes, already present in the genome, or introduced by a virus.

The benefit and the doubt: why monogamy?

Monogamy--a bond between two partners of opposite sex--is a relatively rare phenomenon in mammals (3-5%, from a total of 4000 mammalian species). The duration of the bond may vary from one breeding period to life-long. Monogamy does not exclude 'genetic promiscuity', i.e., extra-pair mating. In fact, this is rather common. Monogamy is an intrinsically unstable mating strategy. Benefits include the (relative) certainty of access to the partner's reproductive potential, but the chief disadvantage is that access to other potential partners is strongly diminished, particularly in those cases where males exhibit strong mate-guarding behavior. Mate-guarding, in particular the guarding by males of females with a good territory or of females that accept the territory of a male, has been shown to be the most important selective pressure leading to the evolution of monogamy. A monogamic bond strongly favors the evolution of male investment in the raising of offspring, as is the case in most birds (90% of bird species are monogamic and most exhibit biparental care of young). Mammals exhibit this type of behavior to a far lesser extent (female mammals monopolize the feeding of newly born young). Most male mammals do not look after their offspring; humans are an exception in this respect. Like most mammals, humans are not strictly monogamic. A tendency to social monogamy has evolved, however, and is subject to strong reinforcement by cultural factors, particularly religion. As a result, in a number of cultures monogamy is the predominant mating system; however, most cultures (about 85%) are polygamic. For humans, the optimal evolutionary strategy is monogamy when necessary, polygamy when possible.

The cook, the thief, his wife and her lover: on the evolution of the human reproductive strategy.

Human reproductive strategy differs from that of most other mammals, including Apes such as the closely related chimpanzee (Pan troglodytes) and the bonobo (Pan paniscus). For example, humans, although basically polygamic, exhibit a strong tendency to (serial) monogamy and--very rare for a mammal--provide biparental care. Moreover, humans are (almost) permanently willing to mate but, in contrast to other species, do so only in private. Unlike chimpanzees and bonobos, the human female exhibits no external signs of ovulation; rather a number of bodily features, e.g. permanently swollen milk glands and the quality of skin and hair, indicate fitness to breed. Human males also exhibit qualities that are rare among mammals: fertile males can be in the company of fertile females without sex being an imperative--although the awareness of sexuality is generally omnipresent. Moreover, unlike most other Apes, human males can cooperate in large groups, in spite of their polygynic inclination and their tendency to compete with each other for access to females. This capacity probably evolved in response to the necessity to acquire food, in particular meat, which was difficult to obtain by a single man. But life in large, complex, multi-male, multi-female groups places great demands on the members' social skills and, to be able to meet these demands, a large, sophisticated brain (neocortex) is needed. Food (and in its wake, cooking) probably forced man to live in ever-larger groups and to evolve the capacity to cooperate. This, in its turn, drove man's present-days psychosocial (emotional and intellectual) make-up. But for this to evolve, an adaptation of reproductive strategy was a conditio sine qua non.

A time to be born and a time to die: reflections on euthanasia.

Euthanasia is, and probably will remain a controversial issue. Although many doctors will agree that under certain circumstances a demand for euthanasia should be granted (and in fact often is granted when the occasion arises), the subject generally gives rise to very emotional debates. Attempts to decriminalize euthanasia generally fail, and this contrasts sharply with the attitude of many towards issues like capital punishment and the objectives of, for example, the military. In this essay this apparent contradiction is discussed from the evolutionary biological point of view. It is argued that euthanasia always concerns the death of a member of some 'in-group' (which in some way we regard as part of ourselves), while capital punishment and the death of (political) enemies always concerns the death of members of some 'out-group'. It is inherent in our genetic make-up, evolved over millions of years, that we oppose the death of members of in-groups and are indifferent to (even promote) the death of members of out-groups. Attempts to regulate these inclinations by cultural and religious wisdom or commands ('[there is] a time to be born and a time to die' and 'love thy enemies like thyself') are only marginally successful, because biological urges generally dominate cultural notions.

Opinions about 'unexplained subfertility'.

The term 'unexplained subfertility' applies to the situation in which a couple, despite serious attempts, does not achieve pregnancy, while according to current knowledge no physiological or anatomical abnormalities can be found. In this paper, possible causes of this phenomenon are reviewed and opinions of six doctors working in the field of reproductive medicine are described. The most significant finding of this study is that all doctors hold personal views with a high level of certainty about the causes of unexplained subfertility. However, they hardly agree with each other! In conclusion, in the field of reproductive medicine there is a dangerous combination of strong personal opinions and much disagreement with regards to unexplained infertility.

Honor your father and your mother.

While on the one hand there is much mutual love and care in the relationship between parents and their offspring, there may, on the other hand, be also much mutual 'sound and fury', which sometimes is far from 'signifying nothing' (William Shakespeare, Macbeth). Indeed, from conception on, individuals are confronted with parent-offspring conflicts of all kinds. Initially these conflicts concern physiological matters (implantation, nutrition, weaning, etc.), but later in life the accent is on psychological ('you must this', 'you must that', 'don't do that' etc.) and social affairs, and phenomena such as child abuse, infanticide and incest may occur. It is, therefore, certainly not self-evident that children honor their parents. To reinforce their position, parents (societies) may appeal to a 'divine' commandment which helps them make their children suppress any tendency to conflict toward them (and hence to their culture), so that children conform to their parents' norms and values. When such psychological and sociological parent-offspring conflicts are not resolved satisfactorily, it can be suggested, children may (consciously or unconsciously) have aggressive feelings toward their parents: Freud's 'Oedipus complex'. This complex, it is argued, can also be seen as a parent-offspring conflict. Given their biological basis, parent-offspring conflicts can hardly be considered as abnormal. Conflicts between adults and their offspring have always existed and will always exist, simply because it is inherent in our genetic make-up: parents and offspring of sexually reproducing species--humans included--are only about 50% genetically related and hence have different interests at all levels of being. Indeed, parent-offspring conflicts are such stuff as we are made on, and our little life is rounded with its consequences (adapted from William Shakespeare, The Tempest).

The immune response during the luteal phase of the ovarian cycle: a Th2-type response?

OBJECTIVE: To test the hypothesis that during the luteal phase of the ovarian cycle, as compared with the follicular phase, the peripheral immune response is shifted toward a type-2 response. DESIGN: Prospective study. SETTING: Academic research setting. PATIENT(S): Women with regular menstrual cycles. INTERVENTION(S): Blood samples were collected between days 6 and 9 of the menstrual cycle and 6-9 days after the LH surge. MAIN OUTCOME MEASURE(S): Intracellular cytokine production of interferon (IFN)-gamma, interleukin (IL)-2, IL-4, and IL-10 after in vitro stimulation of lymphocytes as well as total white blood cell (WBC) count, differential WBC count, and plasma 17 beta-E(2) and P concentrations. RESULT(S): Mean plasma 17 beta-E(2) and P concentrations, WBC count, and mean granulocyte, monocyte, and lymphocyte counts were significantly increased in the luteal phase as compared with the follicular phase of the ovarian cycle. Production of type-1 cytokines (IFN-gamma and IL-2) and production of the type-2 cytokine IL-10 did not vary between the phases of the ovarian cycle. Production of the type-2 cytokine IL-4, however, was significantly increased in the luteal phase as compared with the follicular phase of the ovarian cycle. CONCLUSION(S): During the luteal phase of the ovarian cycle, the immune response is shifted toward a Th2-type response, as reflected by increased IL-4 production in this phase of the cycle. These results may suggest that increased levels of P and 17 beta-E(2) in the luteal phase of the ovarian cycle play a role in the deviation of the immune response toward a type-2 response.

Corticosterone treatment of pregnant low dose endotoxin-treated rats: inhibition of the inflammatory response.

PROBLEM: Can the endotoxin-induced inflammatory response, underlying experimental pre-eclampsia, in pregnant rats be inhibited by corticosterone? METHOD OF STUDY: On day 10 of pregnancy, rats were implanted with pellets containing 25% corticosterone and 75% cholesterol (n = 10) or with 100% cholesterol-pellets (n = 10). On day 14 of pregnancy, rats were infused with either endotoxin (1.0 microg/kg bw) or saline. Three days later, they were sacrificed. Cryostat kidney sections were immunohistologically stained for the presence of neutrophils (PMN) and monocytes (MO) and the expression of inflammation-associated adhesion molecules. RESULTS: In cholesterol-treated rats, endotoxin significantly increased glomerular numbers of PMN and MO, glomerular expression of ICAM-1 and VCAM-1 and glomerular numbers of LFA-1 and VLA-4-positive cells as compared with saline. Corticosterone treatment significantly inhibited glomerular infiltration of PMN, MO and LFA-1 positive cells after endotoxin infusion. It did not affect glomerular ICAM-1 or VCAM-1 expression or numbers of VLA-4 positive cells. CONCLUSIONS: It is concluded that pre-treatment with corticosterone inhibits the low dose endotoxin-induced glomerular inflammatory reaction in pregnant rats, most likely by inhibiting LFA-1 expression, thereby decreasing the adhesiveness of inflammatory cells for activated endothelial cells.

Suppression by developing ovarian follicles of the low-dose endotoxin-induced glomerular inflammatory reaction in the pregnant rat.

OBJECTIVE: In the current study the role of developing ovarian follicles in the control of the endotoxin-induced pregnancy-specific inflammatory reaction was evaluated. STUDY DESIGN: Follicular development was induced in pregnant rats (n = 20) by means of daily intraperitoneal injections of follicle-stimulating hormone from day 11 of pregnancy until the end of the experiment. Control pregnant rats (n = 20) received daily sodium chloride injections. All pregnant rats were infused for 1 hour with either 2 mL endotoxin solution (1.0 microg/kg body weight) or 2 mL sodium chloride solution on day 14 and killed 4 hours or 3 days later. At death, the left kidneys were snap-frozen and immunohistologically stained for the presence of polymorphonuclear leukocytes and monocytes. RESULTS: The results show that in control pregnant rats endotoxin significantly increased glomerular polymorphonuclear leukocyte and monocyte numbers at both 4 hours and 3 days after endotoxin infusion. Induction of follicular development did not affect glomerular polymorphonuclear leukocyte number after endotoxin infusion but significantly decreased the number of monocytes in the glomeruli at both 4 hours and 3 days after endotoxin infusion. CONCLUSION: We conclude that follicles stimulated with follicle-stimulating hormone produce a follicular factor or factors that are able to prevent the endotoxin-induced influx of monocytes into the glomeruli of pregnant rats. It is suggested that these factors play a role in the control of inflammatory processes associated with reproduction, including the disease of pregnancy, preeclampsia.