Biology subjects

Lummaa, V.

Publications and source records attributed to Lummaa, V..

8 recordsLinked to original sources

bioRxiv2026

Megaherbivore mortality risk from temperature extremes is buffered by vegetation productivity but amplified by rainfall

Demographic risks from climate change remain poorly understood for megaherbivore species which face unique challenges because their large food requirements impose strong bottom-up limitation while their small surface-area-to-volume ratio limits heat dissipation. Here, we test how megaherbivore mortality is shaped by the concurrent effects of temperature and rainfall along with vegetation productivity, a potentially critical modifier of climate effects. By analysing four decades of monthly mortality records from 4,457 semi-captive Asian elephants across Myanmar, we identify multiple environmental pathways regulating megaherbivore mortality. Elephant mortality increased at extreme hot and cold temperatures in regions with low annual vegetation productivity, whereas high vegetation productivity buffered against such U-shaped effects of temperature. Furthermore, high rainfall amplified the negative impacts of extreme heat, underlining risks arising from the joint effects of heat and humidity. Seasonal declines in vegetation productivity did not explain the elevated mortality at temperature extremes. Together, our findings show that megaherbivores face elevated risks from global warming, but such risks strongly depend on vegetation productivity and humidity, highlighting multiple pathways through which climate change can shape the dynamics of megaherbivore populations.

ecology↗

bioRxiv2026

Mothers face immediate, but family-size dependent, costs of sons in preindustrial Finland

The expensive son hypothesis posits that mothers incur higher fitness costs when caring for sons versus daughters in species with male-biased size dimorphism. Evidence for maternal survival costs of sons in humans is limited to shortened overall lifespans; whether having more sons reduces short-term survival during reproductive years is unknown. Here, we utilised life-history data from 5,456 mothers from preindustrial Finland to examine whether mothers with more sons had reduced survival within one year of their last birth. While mothers with few children but more sons showed no differences in survival, at higher family sizes, mothers with more sons had increasingly lower survival. These differences peaked at [~]0.4% lower survival per son among mothers with five children, suggesting accumulated physiological costs of sons. These differences then declined and reversed among mothers with more children, potentially due to selective disappearance of frailer mothers. Our results suggest that studies focusing on post-menopausal mothers may bias estimates of the fitness costs of sons and reproductive costs more broadly. We recommend future research further examines the overlooked short-term fitness costs of sons during reproductive years, which is vital for understanding how life-history trade-offs, sexual dimorphism, and their interaction have shaped human evolution.

evolutionary biology↗

bioRxiv2025

Age- and sex-dependent sibling effects on early-life survival in preindustrial humans

Siblings are an important part of an individuals early-life environment and may therefore play an important role in shaping an individuals fitness. The quantification of sibling effects is challenging, especially in long-lived species with extended parental care and overlapping generations, such as humans. Here we quantify how the survival status, age, and sex of older siblings shape childhood survival across 2941 focal individuals born between 1750-1870 using historical parish data from Switzerland. While the total number of older siblings was not associated with an individuals childhood survival, distinguishing between siblings by their survival status, age, and sex revealed several associations, which in some cases also interacted with the sex of the focal individual: While older brothers close in age reduced the survival of girls but not boys, having more older sisters born close in age improved their younger siblings survival. Our results, therefore, show that sibling interactions play an important role in shaping early-life survival, and highlight that the strength and direction of these effects are context-dependent and can arise through biological and cultural factors. We encourage future studies on sibling interaction to consider siblings survival, age and sex, in both humans and other species.

evolutionary biology↗

bioRxiv2025

Genetic variation in life-history traits is not correlated with estrogen-receptor positive breast cancer risk

Estrogen receptor-positive breast cancer (ER+ BC) is one of the most prevalent cancers, but the evolutionary processes shaping genetic variation in ER+ BC risk are poorly understood. Both evolutionary life-history theory and evidence from studies of individual ER+ BC risk variants suggest that increased genetic ER+ BC risk is associated with faster maturation, earlier reproduction, and/or increased reproductive success (i.e., there is a trade-off), but it is unclear how well this pattern is replicated when considering the polygenic architecture of these traits after controlling for potential biases. Here, we estimate genome-wide genetic correlations between ER+ BC risk and three reproductive traits (age at menarche, age at first birth, and the number of children) using genomic restricted maximum-likelihood analyses on Lifelines biobank data and linkage disequilibrium score regressions on population and family-based genome-wide association study data. Regardless of the data or method used, genetic correlations were low and not statistically significant. Further analyses decomposing genome-wide genetic variance into local regions detected only three loci exhibiting significant pleiotropy between ER+ BC risk and age at menarche, suggesting little shared genetic architecture between ER+ BC risk and reproductive traits. Thus, the role of life-history trade-offs in shaping ER+ BC risk in European populations appears, at most, small, and the evolutionary processes giving rise to this life-threatening disease remain unclear. Future studies could examine the impact of evolutionary mismatches in shaping ER+ BC risk, where conducting longitudinal studies on populations transitioning to reproductive patterns observed in contemporary European populations would be most useful.

evolutionary biology↗

bioRxiv2024

Lifespan costs of reproduction increase during the Great Finnish Famine

Evolutionary theory of aging predicts that women with increased reproductive effort live shorter lives, but evidence is inconsistent. These inconsistencies could be because environmental conditions influence how much a mothers life span is reduced when having more children, i.e. their life-span cost of reproduction. Using a structural equation measurement model, we compare how reproductive effort affects the life span of 4,684 women exposed across different life-stages, or not at all, to the Great Finnish Famine. We find that life span costs of reproduction became higher in mothers exposed to the famine during reproduction, and for these mothers amounted to lower life expectancy of [~]0.5 years per child. Conversely, reproduction did not shape the life spans of mothers not exposed to the famine, or exposed post-reproduction or during development. This natural experiment reveals how environmental adversity can influence reproductive costs, providing a biological explanation for previous inconsistent findings, while showing how reproductive behavior has shaped the evolution of aging in humans. TEASERMothers with more children had shorter lives during a famine, suggesting that harsh conditions increase costs of reproduction.

evolutionary biology↗

bioRxiv2024

Menopause has not evolved as a general trait in mammals: A response to "Do mammals have menopause?"

Reproductive senescence is widespread across mammals, but only a small number of species have physiological reproductive cessation and an extended post-reproductive lifespan. A recent commentary in Cell by Winkler & Goncalves (2023) suggests that menopause is actually a widespread trait of mammals, which would change our understanding of senescence and have implications for the study of menopause in humans. Here, we identify three main issues with the methodology of this commentary: the use of captive populations, the use of maximal lifespan, and misinterpretations of the data sources. We show that this methodology does not support the conclusions at the species-level, and conclude that, in line with the predictions of classic life-history theory, menopause is indeed a rare trait.

evolutionary biology↗

bioRxiv2022

Lifetime reproductive success is an imprecise but largely unbiased predictor of long-term genetic contribution in historical humans

An individuals lifetime reproductive success (LRS) measures its realised genetic contributions to the next generation, but how well does it predict these over longer periods? Here we use human genealogical data to estimate expected individual genetic contributions (IGC) and quantify the degree to which LRS, relative to other fitness proxies, predicts IGC over longer periods in natural populations. This allows an identification of the life-history stages that are most important in shaping variation in IGC. We use historical genealogical data from two non-isolated local populations in Switzerland to estimate the stabilised IGC for 2,230 individuals ~10 generations after they were born. We find that LRS explains 30% less variation in IGC than the best predictor of IGC, the number of grandoffspring. However, albeit less precise than the number of grandoffspring, we show that LRS does provide an unbiased prediction of IGC and overall predicts IGC better than lifespan and similarly when accounting for offspring survival to adulthood. Overall, our findings demonstrate the value of human genealogy data to evolutionary biology and showing that reproduction - more than lifespan or offspring survival - impacts the long-term genetic contributions of historic humans, even in a population with appreciable migration.

evolutionary biology↗

bioRxiv2020

Sex-specific body mass ageing trajectories in adult Asian elephants

In species with marked sexual dimorphism and where one sex undergoes stronger intrasexual competition, that sex is expected to age earlier or quicker. Here, we utilise a unique, longitudinal dataset of a semi-captive population of Asian elephants (Elephas maximus), a species with marked male-biased intrasexual competition, with males being larger and living shorter, and test the hypothesis that males show earlier and/or faster body mass ageing than females. We show sex-specific body mass ageing trajectories: adult males gained weight up to the age of 48 years old, followed by a decrease in body mass until natural death. In contrast, adult females gained body mass with age until a body mass decline in the last year of life. Our study shows that sex-specific life-histories shape ageing patterns, consistent with the predictions of the classical theory of ageing.

evolutionary biology↗