Menopause: No support for an evolutionary explanation among historical Norwegians

Skjærvø, Gine Roll

doi:10.1016/j.exger.2013.02.001

Cited by 11 publications

(8 citation statements)

References 70 publications

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“…The extent to which intergenerational overlaps in reproduction are costly is a question of much empirical debate that has yet to be resolved (Lahdenperä et al, 2012; Mace & Alvergne, 2012; Skjærvø & Røskaft, 2013). We have also assumed that senescence is an extrinsic process rather than one directly under selection.…”

Section: Discussionmentioning

confidence: 99%

Intergenerational conflicts may help explain parental absence effects on reproductive timing: a model of age at first birth in humans

Moya

Sear

2014

PeerJ

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Background. Parental absences in childhood are often associated with accelerated reproductive maturity in humans. These results are counterintuitive for evolutionary social scientists because reductions in parental investment should be detrimental for offspring, but earlier reproduction is generally associated with higher fitness. In this paper we discuss a neglected hypothesis that early reproduction is often associated with parental absence because it decreases the average relatedness of a developing child to her future siblings. Family members often help each other reproduce, meaning that parents and offspring may find themselves in competition over reproductive opportunities. In these intergenerational negotiations offspring will have less incentive to help the remaining parent rear future half-siblings relative to beginning reproduction themselves.Method. We illustrate this “intergenerational conflict hypothesis” with a formal game-theoretic model.Results. We show that when resources constrain reproductive opportunities within the family, parents will generally win reproductive conflicts with their offspring, i.e., they will produce more children of their own and therefore delay existing offsprings’ reproduction. This is due to the asymmetric relatedness between grandparents and grandchildren (r = .25), compared to siblings (r = 0.5), resulting in greater incentives for older siblings to help rear younger siblings than for grandparents to help rear grandchildren. However, if a parent loses or replaces their partner, the conflict between the parent and offspring becomes symmetric since half siblings are as related to one another as grandparents are to grandchildren. This means that the offspring stand to gain more from earlier reproduction when their remaining parent would produce half, rather than full, siblings. We further show that if parents senesce in a way that decreases the quality of their infant relative to their offspring’s infant, the intergenerational conflict can shift to favor the younger generation.

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Section: Discussionmentioning

confidence: 99%

Intergenerational conflicts may help explain parental absence effects on reproductive timing: a model of age at first birth in humans

Moya

Sear

2014

PeerJ

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“…Recent tests of the reproductive conflict hypothesis in humans have yielded mixed results [71][72][73][74]. Two studies have found evidence of the costs of reproductive conflict (also see [53]).…”

Section: Reviewmentioning

confidence: 99%

The evolution of prolonged life after reproduction

Croft

Brent

Franks

et al. 2015

Trends in Ecology & Evolution

167

169

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Why females of some species cease ovulation before the end of their natural lifespan is a longstanding evolutionary puzzle. For many species in captivity, post-reproductive life is simply an epiphenomenon of lengthened lifespan. Yet in natural populations of humans as well as some cetaceans and insects, reproductive senescence occurs much faster than somatic aging and females exhibit prolonged post-reproductive lifespans (PRLSs). Determining the mechanisms and functions that underpin PRLSs has proved a significant challenge. Here we bring together both classic and modern hypotheses proposed to explain PRLSs and discuss their application to both human and nonhuman animals. By taking an integrative and broad taxonomic approach we highlight the need to consider multiple interacting explanations for the evolution of PRLSs.

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“…Both populations comprised two distinct socioeconomic groups and each individual belonged to either a low ( poor) or high (wealthy) status group [26,27]. The chief demographic characteristics of both populations during the study period can be described as strictly monogamous, where both men and women married late and experienced moderate infant mortality and natural fertility [32].…”

Section: Materials and Methods (A) Study System And Data Collectionmentioning

confidence: 99%

Solar activity at birth predicted infant survival and women's fertility in historical Norway

Skjærvø

Fossøy

2015

Proc. R. Soc. B.

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Ultraviolet radiation (UVR) can suppress essential molecular and cellular mechanisms during early development in living organisms and variations in solar activity during early development may thus influence their health and reproduction. Although the ultimate consequences of UVR on aquatic organisms in early life are well known, similar studies on terrestrial vertebrates, including humans, have remained limited. Using data on temporal variation in sunspot numbers and individual-based demographic data (N ¼ 8662 births) from Norway between 1676 and 1878, while controlling for maternal effects, socioeconomic status, cohort and ecology, we show that solar activity (total solar irradiance) at birth decreased the probability of survival to adulthood for both men and women. On average, the lifespans of individuals born in a solar maximum period were 5.2 years shorter than those born in a solar minimum period. In addition, fertility and lifetime reproductive success (LRS) were reduced among low-status women born in years with high solar activity. The proximate explanation for the relationship between solar activity and infant mortality may be an effect of folate degradation during pregnancy caused by UVR. Our results suggest that solar activity at birth may have consequences for human lifetime performance both within and between generations.

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Menopause: No support for an evolutionary explanation among historical Norwegians

Cited by 11 publications

References 70 publications

Intergenerational conflicts may help explain parental absence effects on reproductive timing: a model of age at first birth in humans

Intergenerational conflicts may help explain parental absence effects on reproductive timing: a model of age at first birth in humans

The evolution of prolonged life after reproduction

Solar activity at birth predicted infant survival and women's fertility in historical Norway

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