Why and how do we age?
Patrick Rabbitt in The Aging Mind, 2019
Sexual reproduction combines genes from different individuals and so makes each birth a new experiment in survival. Darwin’s big idea was that if altered genetic legacies (mutations) are unhelpful, they lower the odds that the individual animals that carry them will live long enough to pass them forward along the species timeline. Carriers of helpful mutations are more likely to survive to breed and so make their individual novel inheritances a common legacy. Without mutations a species would remain fixed over time. Stasis would be an option for a species perfectly adapted to an everlastingly unchanging world – but no paradise is future-proof. The world changes continually, and drastically, and species that cannot meet new threats or seize new advantages are locked in ruts that they may cosily inhabit for millennia but within which they will perish when dire changes inevitably occur.
Human mate selection theory
John Ravenscroft in The Routledge Handbook of Visual Impairment, 2019
The gender differences related to what women seek in male partners have also been demonstrated as universal traits across cultures with evolutionary roots that go back to the beginning of sexual reproduction (Buss, 1989; Kenrick and Keefe, 1992). Women’s preferences are complex. One reason for this, from an evolutionary psychological perspective, is reproductive biology. Males can replenish their supply of sex cells and reproduce a number of times that is limited only by the number of fertile females available to have sex with them (Buss, 2016). Females, however, have a fixed number of ova that cannot be replenished (Buss, 2016). Also, when pregnancy does occur, females are committed to the investment of the nine-month gestation process (Buss, 2016). Females hold exceptionally valuable and limited resources when taking these factors into account. Thus, women are highly selective in the mating process having been imprinted by evolutionary forces. For women, the stakes are extremely high in the mate selection process and, for these reasons, the responsibility for choosing a mate falls to them (Fedigan, 1992). The preferences females seek in a mate give the utmost importance to financial resources and social status as opposed to males’ high-ranking preferences for signs of physical health, attractiveness and youthfulness (Feingold, 1992; Fletcher, 2002; Geary, 2010).
A fateful attachment: Family life: from necessities to niceties
Derek Steinberg in Consciousness Reconnected, 2018
Or the advantages of meiosis metamorphose into the incest taboo. It may appear fanciful to relate sexual reproduction (meiosis) at the cellular level to species behaviour. But it was meiosis that enabled the mixing of genes and diversity that could not happen in asexual reproduction (i.e. identical cloning) and diversity being the first essential step in evolution it is conceivable that sexual reproduction at the single cell level acts in reciprocity with sexual reproduction at the behavioural level, which, if you add to this the complex, cultural rites, rituals and sophistication associated with sex, makes the idea of our ‘learning’ from the protozoan not all that far fetched. Thus the possible remote roots of the widespread inhibitions, personal as well as cultural, on sexual relationships between close relatives. Again, we should not read that the wrong way round: the taboo didn’t ‘prevent’ incest; it is more likely that incestuous relationships didn’t do well, in terms of descendants, and those with a taboo which might have been in the minority and regarded as anomalous ended up with the most descendants.
An overview of sex and reproductive immunity from an evolutionary/anthropological perspective
Published in Immunological Medicine, 2021
Yoshihiko Araki, Hiroshi Yoshitake, Kenji Yamatoya, Hiroshi Fujiwara
Nevertheless, life on Earth must coexist with viruses, such as SERS-CoV-2, the cause of the recent pandemic [42]. Viruses may be at odds with life and are clearly not mutually beneficial. This can be said to be an everyday phenomenon in terms of the geological time scale. Before the emergence of sex, eukaryotic cells developed via symbiotic relationships with prokaryotes that became intracellular organelles, according to the endosymbiotic theory [43–45]. Specifically, mitochondria and chloroplasts were derived from aerobic bacteria and cyanobacteria, respectively. Eukaryotes, such as plants and animals, then evolved to undergo sexual reproduction. Furthermore, mammals developed a reproductive strategy that exploits the immune system by acquiring an unusual organ called the placenta, which is possibly the result of a virus being lodged in a mammalian ancestor. What is the destination of human prosperity and evolution through sexual reproduction? If we consider these issues from the perspective of both human cultural and biological histories, we may be able to see a slightly different side to the common sense of the past.
Repeated administrations of Mn3O4 nanoparticles cause testis damage and fertility decrease through PPAR-signaling pathway
Published in Nanotoxicology, 2020
Xiao Zhang, Zongkai Yue, Haijun Zhang, Lu Liu, Xiaomeng Zhou
It is well known that spermatozoa are produced from spermatogonial stem cells by a series of process involving mitosis, meiosis and cellular differentiation, and spermatogenesis is essential for sexual reproduction (Oliva and Castillo 2011). Meanwhile, spermatogenesis process is subjected to the neuroendocrine hypothalamic-pituitary-gonadal (HPG) axis (Huleihel and Lunenfeld 2004). In addition, hormones secreted by hypothalamus are transported to the pituitary gland via the blood and then induce the production and secretion of gonadotropins which in turn are transported to testes by the blood (Kong et al. 2014). LH stimulates the Leydig cells in the testes to synthesize and secrete the testosterone (Li et al. 2013). FSH and T stimulate Sertoli cells to produce androgen binding protein and improve the formation of the BTB, meanwhile, FSH and T could support and nourish the sperm cells during their maturation (Sofikitis et al. 2008). In this study, the serum T, FSH, and LH levels in serum of rats were determined to investigate the effect of Mn3O4-NPs on sex hormones. The serum T and FSH levels were significantly decreased in Mn3O4-NPs-120 d compared with those in the Mn3O4-NPs-0 d and Mn3O4-NPs-60 d, indicating that the serum T and FSH were suppressed in a time-dependent manner after administrated with Mn3O4-NPs. All results suggest that Mn3O4-NPs can disturb the normal HPG axis function which correlated with the malfunction in spermatogenesis and male infertility.
Queering the Common Core (and the NGSS): Challenging Normativity and Embracing Possibility
Published in Journal of Homosexuality, 2022
Allison Mattheis, Joel Lovos, Carly Humphrey, Lindsey Eichenberger, Christina Restrepo Nazar
Teachers can be careful to avoid anthropormophizing non-human organisms—although male seahorses carry offspring, this does not make them “dads,” for example. Teaching sexual reproduction in plants offers another opportunity to detach assumptions of gender from anatomy. Queering this discussion involves the understanding of sex categories in plants as a distinction between two structures with functions for reproduction. There are no value judgments on these categories other than their function, a concept that can inform the understanding of sex categories in humans. When we detach understandings of gender from processes of sexual reproduction, we understand that organisms have functional parts that do not define social identity. Educators can teach and uphold this concept in their classrooms as a practice of inclusivity, especially for students who do not rely on their assigned sex categories to identify their personhood. These findings directly respond to other research that showcases the dominance of heteronormative reproductive curriculum in schools and challenges that dominance (Gunckel, 2019).