Postnatal depression and reproductive success in modern, low-fertility contexts

Background and objectives: Postnatal depression (PND) presents a puzzling phenomenon to evolutionary anthropologists as it is highly prevalent and yet detrimental to child development and maternal health. Adaptive explanations have been proposed, but have not been tested with data that directly link PND to female fertility. Methodology: A survey was designed to gather complete reproductive histories and retrospective measures of PND to measure the effects of PND on fitness. Respondents were born between 1930 and 1967, with the majority based in the UK during their childrearing years. The hypothesis that PND is detrimental to fitness is assessed using Mann–Whitney U tests on completed fertility. Binary logistic regression modelling is used to test the hypothesis that PND reduces the likelihood of parity progression. Results: Women experiencing PND at their first or second birth have lower completed fertility, with PND at the first birth leading to lowered fertility. Logistic regression analyses show that this is the result of reductions in the likelihood of parity progression to a third birth when PND is experienced at the first birth or when repeat bouts occur. Conclusions and implications: Our results call into question adaptationist arguments, contribute to the growing understanding of the importance of emotional wellbeing to fertility decision making, and given the economic consequences of markedly below replacement fertility, highlight a potential new source of financial incentive to invest in screening and preventative measures to ensure good maternal mental health

Current Demographics Suggest Future Energy Supplies Will Be Inadequate to Slow Human Population Growth

Influential demographic projections suggest that the global human population will stabilize at about 9–10 billion people by mid-century. These projections rest on two fundamental assumptions. The first is that the energy needed to fuel development and the associated decline in fertility will keep pace with energy demand far into the future. The second is that the demographic transition is irreversible such that once countries start down the path to lower fertility they cannot reverse to higher fertility. Both of these assumptions are problematic and may have an effect on population projections. Here we examine these assumptions explicitly. Specifically, given the theoretical and empirical relation between energy-use and population growth rates, we ask how the availability of energy is likely to affect population growth through 2050. Using a cross-country data set, we show that human population growth rates are negatively related to per-capita energy consumption, with zero growth occurring at ∼13 kW, suggesting that the global human population will stop growing only if individuals have access to this amount of power. Further, we find that current projected future energy supply rates are far below the supply needed to fuel a global demographic transition to zero growth, suggesting that the predicted leveling-off of the global population by mid-century is unlikely to occur, in the absence of a transition to an alternative energy source. Direct consideration of the energetic constraints underlying the demographic transition results in a qualitatively different population projection than produced when the energetic constraints are ignored. We suggest that energetic constraints be incorporated into future population projections

Socio-Economic Instability and the Scaling of Energy Use with Population Size

The size of the human population is relevant to the development of a sustainable world, yet the forces setting growth or declines in the human population are poorly understood. Generally, population growth rates depend on whether new individuals compete for the same energy (leading to Malthusian or density-dependent growth) or help to generate new energy (leading to exponential and super-exponential growth). It has been hypothesized that exponential and super-exponential growth in humans has resulted from carrying capacity, which is in part determined by energy availability, keeping pace with or exceeding the rate of population growth. We evaluated the relationship between energy use and population size for countries with long records of both and the world as a whole to assess whether energy yields are consistent with the idea of an increasing carrying capacity. We find that on average energy use has indeed kept pace with population size over long time periods. We also show, however, that the energy-population scaling exponent plummets during, and its temporal variability increases preceding, periods of social, political, technological, and environmental change. We suggest that efforts to increase the reliability of future energy yields may be essential for stabilizing both population growth and the global socio-economic system

Extracerebral metastases determine the outcome of patients with brain metastases from renal cell carcinoma

<p>Abstract</p> <p>Background</p> <p>In the era of cytokines, patients with brain metastases (BM) from renal cell carcinoma had a significantly shorter survival than patients without. Targeted agents (TA) have improved the outcome of patients with metastatic renal cell carcinoma (mRCC) however, their impact on patients with BM is less clear. The aim of this analysis was to compare the outcome of patients with and without BM in the era of targeted agents.</p> <p>Methods</p> <p>Data from 114 consecutive patients who had access to targeted agent were analyzed for response rates (ORR), progression free survival (PFS) and overall survival (OS). All patients diagnosed with BM underwent local, BM-specific treatment before initiation of medical treatment.</p> <p>Results</p> <p>Data of 114 consecutive patients who had access to at least one type of targeted agents were analyzed. Twelve out of 114 renal cell carcinoma (RCC) patients (10.5%) were diagnosed with BM. Systemic treatment consisted of sunitinib, sorafenib, temsirolimus or bevacizumab. The median PFS was 8.7 months (95% CI 5.1 - 12.3) and 11.4 months (95% CI 8.7 - 14.1) for BM-patients and non-BM-patients, respectively (p = 0.232). The median overall survival for patients with and without BM was 13.4 (95% CI 1- 43.9) and 33.3 months (95% CI 18.6 - 47.0) (p = 0.358), respectively. No patient died from cerebral disease progression. ECOG Performance status and the time from primary tumor to metastases (TDM) were independent risk factors for short survival (HR 2.74, p = 0.001; HR: 0.552, p = 0.034).</p> <p>Conclusions</p> <p>Although extracerebral metastases determine the outcome of patients with BM, the benefit from targeted agents still appears to be limited when compared to patients without BM.</p

Ecological Constraints and Life History Tradeoffs among Human Foragers and their Prey

This dissertation attempts to identify ecological relationships useful for understanding large-scale patterns in human-environment interaction that can be applied to archaeological studies. It uses three established bodies of theory to understand ecological constraints and life history tradeoffs, applying the same basic framework to human adaptations and the demographic trends of other mammals. First, a model from optimal foraging theory (the marginal value theorem), which posits a tradeoff between resource availability and resource processing, is applied to zooarchaeology to understand human butchery patterns. Humans tend to butcher prey according to the predictions of the model in both ethnographic and archaeological settings: they process carcasses more intensively when prey are rare. Moreover, evaluation of the statistical and taphonomic factors that could affect prehistoric faunal data demonstrates that even coarse-measures of butchery intensity can uncover the predicted tradeoff. Life history theory can link energetic and environmental constraints to demographic parameters and is therefore useful for understanding the unique features of humans that may have been responsible for their geographic expansion in addition to how their prey might adjust to changes in mortality or energy availability. Lifetime reproductive effort captures the tradeoffs among adult size, lifespan, and reproductive effort to yield an aggregate dimensionless measure highly useful for summarizing the life histories of different organisms for cross-species comparison. The second study in this dissertation examines lifetime reproductive effort to see if humans have diverged from most mammals with respect to this important life history metric. This measure shows that while we (humans) differ in many individual life history attributes, in the aggregate we converge on the same optimal solution as other organisms, given simple constraints on production and mortality. This suggests that some of the unique features of humans (post-reproductive lifespans, extensive food-sharing, and long juvenile periods) have not caused a divergence from the factors constraining other optimal life histories. While humans have re-organized the lifespan, allocation of energy to reproduction during the lifespan is nonetheless constrained by some fundamental ecological constraint. This helps place human life history evolution in a broader context for understanding the causes and consequences of the factors that allowed humans to diverge from other mammals. General patterns between body size, abundance, and geographical area exist in ecology that can help archaeologists understand how prey respond demographically to changes in resource availability and/or predation pressure. Following this motivation the third study uses population viability analysis (PVA) to explore the causes of relative extinction risk among terrestrial mammals. The model predicts that relative extinction risk is a peaked function of body mass such that risk is minimized at about 100 grams, which is near the modal size in continental faunas and the size that species colonizing islands from continental mainlands converge upon. This suggests that the model captures a key feature of the dynamics governing the evolution of size and probability of extinction. It also applies to life history evolution by demonstrating that variation in growth rate, population density, and generation length interact such that an optimal strategy exists for staying in the ‘evolutionary game’ (i.e., avoiding extinction). Debates about the loss of Pleistocene megafauna center on climate and human hunting as opposing causes. The model provides modest support for the view that humans may be responsible for the bias towards large body size in the extinct species. The model is also useful for understanding the demographic attributes of human prey, generally, and has many further applications for understanding life history evolution and population stability in humans and other mammals. Across the three studies a number of useful tools are developed for identifying large-scale tradeoffs that can be used to understand human population dynamics, foraging behavior, and their implications for resource use and geographic range expansion. The same set of techniques is also useful for uncovering the connections between human attributes and those of the species they influence via predation and/or the altering of ecosystems. These techniques are valuable theoretical developments for the building of a more robust environmental and/or ecological archaeology (anthropology).Doctor of AnthropologyDoctoralAnthropologyBoone, JamesHuckell, BrucePearson, OsbjornBrown, Jame

On size and extinction: a random walk model predicts the body size of lowest risk for mammals

Question: Is the relationship between extinction risk and size in terrestrial mammals described by a peaked function or a monotonic function? Mathematical method: We develop a population viability analysis model where species take random walks at generational time steps. The model works like the classic gambler’s ruin problem where risky combinations of variance in growth rate, population density, and generation length are eliminated from an evolutionary game. Key assumptions: Our model ignores speciation. It assumes that the population growth rate at evolutionary time scales is zero. It assumes an unbiased random walk. Chronological time is adjusted for generation length, so that longer-lived species make fewer ‘gambles’ in the same period of time. Conclusions: Particular combinations of variance in growth rate and average population density yield an extinction function that predicts a size of lowest relative extinction risk for terrestrial mammals. This size is close to the mode of continental body size distributions (at about 0.1 kg). Generation length is a fundamental evolutionary time scale