Selection for Increased Brood Size in Historical Human Populations

Helle, Samuli; Lummaa, Virpi; Jokela, Jukka

doi:10.1111/j.0014-3820.2004.tb01658.x

Cited by 20 publications

(21 citation statements)

References 36 publications

(56 reference statements)

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“…We have previously shown that, historically, twin births often enhanced female fitness in humans (25,30,45), and recently Lahdenperä et al (31) reported positive selection on female postreproductive lifespan in the same populations of Finns. If long postreproductive lifespan indeed brought fitness benefits to the females, twinning may have been selected against in historical human populations where the risk of infection was high.…”

Section: Discussionmentioning

confidence: 93%

Accelerated immunosenescence in preindustrial twin mothers

Helle

Lummaa

Jokela

2004

Proc. Natl. Acad. Sci. U.S.A.

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Life-history theory predicts a tradeoff between reproductive effort and lifespan. It has been suggested that this tradeoff is a result of reproductive costs accelerating senescence of the immune system, leading to earlier death. Longevity costs of reproduction are suggested for some human populations, but whether high reproductive effort leads to impaired immune function is unknown. We examined how reproductive effort affected postreproductive survival and the probability of dying of an infectious disease in women born in preindustrial Finland between 1702 and 1859. We found that mothers delivering twins had reduced postreproductive survival after age 65. This effect arose because mothers of twins had a higher probability of succumbing to an infectious disease (mainly tuberculosis) than mothers delivering singletons. The risk among mothers of twins of dying of an infectious disease was further elevated if mothers had started reproducing early. In contrast, neither female postreproductive survival nor the risk of succumbing to an infectious disease was influenced by the total number of offspring produced. Our results provide evidence of a long-term survival cost of twinning in humans and indicate that the mechanism mediating this cost might have been accelerated immunosenescence.immune function ͉ cost of reproduction ͉ longevity ͉ reproductive effort ͉ tuberculosis

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Section: Discussionmentioning

confidence: 93%

Accelerated immunosenescence in preindustrial twin mothers

Helle

Lummaa

Jokela

2004

Proc. Natl. Acad. Sci. U.S.A.

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“…According to the ‘natural selection’ hypothesis, women who are predisposed to having twins are more likely to produce them in a healthy reproductive environment (Helle et al, 2004; Lummaa et al, 1998). Since variation in twinning is mostly due to differences in DZ twinning rates, and favorable reproductive conditions would be expected to result in more robust phenotypes in offspring, our findings of a greater height and BMI in DZ twins are in line with this hypothesis.…”

Section: Discussionmentioning

confidence: 99%

Zygosity Differences in Height and Body Mass Index of Twins From Infancy to Old Age: A Study of the CODATwins Project

et al. 2015

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A trend toward greater body size in dizygotic (DZ) than in monozygotic (MZ) twins has been suggested by some but not all studies, and this difference may also vary by age. We analyzed zygosity differences in mean values and variances of height and body mass index (BMI) among male and female twins from infancy to old age. Data were derived from an international database of 54 twin cohorts participating in the COllaborative project of Development of Anthropometrical measures in Twins (CODATwins), and included 842,951 height and BMI measurements from twins aged 1 to 102 years. The results showed that DZ twins were consistently taller than MZ twins, with differences of up to 2.0 cm in childhood and adolescence and up to 0.9 cm in adulthood. Similarly, a greater mean BMI of up to 0.3 kg/m2 in childhood and adolescence and up to 0.2 kg/m2 in adulthood was observed in DZ twins, although the pattern was less consistent. DZ twins presented up to 1.7% greater height and 1.9% greater BMI than MZ twins; these percentage differences were largest in middle and late childhood and decreased with age in both sexes. The variance of height was similar in MZ and DZ twins at most ages. In contrast, the variance of BMI was significantly higher in DZ than in MZ twins, particularly in childhood. In conclusion, DZ twins were generally taller and had greater BMI than MZ twins, but the differences decreased with age in both sexes.

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“…The calculation of λ is quite straightforward and its use can be substituted for LRS-based measures, as has been done in a number of studies already (Korpelainen, 2003; Helle, Lummaa, & Jokela, 2004). Korpelainen (2003) notes that while LRS declined in historical Finland, λ actually remained remarkably constant, suggesting that families were successfully negotiating a fertility-survival trade-off and achieving the same mean fitness with lower fertility.…”

Section: Discussionmentioning

confidence: 99%

The marginal valuation of fertility

Jones¹,

Bird²

2014

Evolution and Human Behavior

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Substantial theoretical and empirical evidence demonstrates that fertility entails economic, physiological, and demographic trade-offs. The existence of trade-offs suggests that fitness should be maximized by an intermediate level of fertility, but this hypothesis has not had much support in the human life-history literature. We suggest that the difficulty of finding intermediate optima may be a function of the way fitness is calculated. Evolutionary analyses of human behavior typically use lifetime reproductive success as their fitness criterion. This fitness measure implicitly assumes that women are indifferent to the timing of reproduction and that they are risk-neutral in their reproductive decision-making. In this paper, we offer an alternative, easily-calculated fitness measure that accounts for differences in reproductive timing and yields clear preferences in the face of risky reproductive decision-making. Using historical demographic data from a genealogically-detailed dataset from 19th century Utah, we show that this measure is highly concave with respect to reproductive effort. This result has three major implications: (1) if births are properly timed, a lower-fertility reproductive strategy can have the same fitness as a high-fertility strategy, (2) intermediate optima are far more likely using fitness measures that are strongly concave with respect to effort, (3) we expect mothers to have strong investment preferences with respect to the risk inherent in reproduction.

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Selection for Increased Brood Size in Historical Human Populations

Cited by 20 publications

References 36 publications

Accelerated immunosenescence in preindustrial twin mothers

Accelerated immunosenescence in preindustrial twin mothers

Zygosity Differences in Height and Body Mass Index of Twins From Infancy to Old Age: A Study of the CODATwins Project

The marginal valuation of fertility

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