Thomas E. Dickins

Evolutionary Theory and the Ultimate–Proximate Distinction in the Human Behavioral Sciences

To properly understand behavior, we must obtain both ultimate and proximate explanations. Put briefly, ultimate explanations are concerned with why a behavior exists, and proximate explanations are concerned with how it works. These two types of explanation are complementary and the distinction is critical to evolutionary explanation. We are concerned that they have become conflated in some areas of the evolutionary literature on human behavior. This article brings attention to these issues. We focus on three specific areas: the evolution of cooperation, transmitted culture, and epigenetics. We do this to avoid confusion and wasted effort—dangers that are particularly acute in interdisciplinary research. Throughout this article, we suggest ways in which misunderstanding may be avoided in the future.

Early-life conditions and age at first pregnancy in British women

There is growing evidence that the reproductive schedules of female mammals can be affected by conditions experienced during early development, with low parental investment leading to accelerated life-history strategies in the offspring. In humans, the relationships between early-life conditions and timing of puberty are well studied, but much less attention has been paid to reproductive behaviour. Here, we investigate associations between early-life conditions and age at first pregnancy (AFP) in a large, longitudinally studied cohort of British women (n = 4553). Low birthweight for gestational age, short duration of breastfeeding, separation from mother in childhood, frequent family residential moves and lack of paternal involvement are all independently associated with earlier first pregnancy. Apart from that of birthweight, the effects are robust to adjustment for family socioeconomic position (SEP) and the cohort members mothers age at her birth. The association between childhood SEP and AFP is partially mediated by early-life conditions, and the association between early-life conditions and AFP is partially mediated by emotional and behavioural problems in childhood. The overall relationship between early-life adversities and AFP appears to be approximately additive.

THE NICHE CONSTRUCTION PERSPECTIVE: A CRITICAL APPRAISAL

Niche construction refers to the activities of organisms that bring about changes in their environments, many of which are evolutionarily and ecologically consequential. Advocates of niche construction theory (NCT) believe that standard evolutionary theory fails to recognize the full importance of niche construction, and consequently propose a novel view of evolution, in which niche construction and its legacy over time (ecological inheritance) are described as evolutionary processes, equivalent in importance to natural selection. Here, we subject NCT to critical evaluation, in the form of a collaboration between one prominent advocate of NCT, and a team of skeptics. We discuss whether niche construction is an evolutionary process, whether NCT obscures or clarifies how natural selection leads to organismal adaptation, and whether niche construction and natural selection are of equivalent explanatory importance. We also consider whether the literature that promotes NCT overstates the significance of niche construction, whether it is internally coherent, and whether it accurately portrays standard evolutionary theory. Our disagreements reflect a wider dispute within evolutionary theory over whether the neo‐Darwinian synthesis is in need of reformulation, as well as different usages of some key terms (e.g., evolutionary process).

The extended evolutionary synthesis and the role of soft inheritance in evolution

In recent years, a number of researchers have advocated extending the modern synthesis in evolutionary biology. One of the core arguments made in favour of an extension comes from work on soft inheritance systems, including transgenerational epigenetic effects, cultural transmission and niche construction. In this study, we outline this claim and then take issue with it. We argue that the focus on soft inheritance has led to a conflation of proximate and ultimate causation, which has in turn obscured key questions about biological organization and calibration across the life span to maximize average lifetime inclusive fitness. We illustrate this by presenting hypotheses that we believe incorporate the core phenomena of soft inheritance and will aid in understanding them.

Birthweight and paternal involvement predict early reproduction in British women: Evidence from the National Child Development Study

There is considerable interest in the mechanisms maintaining early reproduction in the most socioeconomically disadvantaged groups in developed countries. Previous research has suggested that differential exposure to early‐life factors such as low birthweight and lack of paternal involvement during childhood may be relevant. Here, we used longitudinal data on the female cohort members from the UK National Child Development Study (n = 3,014–4,482 depending upon variables analyzed) to investigate predictors of early reproduction. Our main outcome measures were having a child by age 20, and stating at age 16 an intended age of reproduction of 20 years or lower. Low paternal involvement during childhood was associated with increased likelihood of early reproduction (O.R. 1.79–2.25) and increased likelihood of early intended reproduction (O.R. 1.38–2.50). Low birthweight for gestational age also increased the odds of early reproduction (O.R. for each additional s.d. 0.88) and early intended reproduction (O.R. for each additional s.d. 0.81). Intended early reproduction strongly predicted actual early reproduction (O.R. 5.39, 95% CI 3.71–7.83). The results suggest that early‐life factors such as low birthweight for gestational age, and low paternal involvement during childhood, may affect womens reproductive development, leading to earlier target and achieved ages for reproduction. Differential exposure to these factors may be part of the reason that early fertility persists in socioeconomically disadvantaged groups. We discuss our results with respect to the kinds of interventions likely to affect the rate of teen pregnancy. Am. J. Hum. Biol., 2010.

Synthesis in the human evolutionary behavioural sciences

Over the last three decades, the application of evolutionary theory to the human sciences has shown remarkable growth. This growth has also been characterised by a ‘splitting’ process, with the emergence of distinct sub-disciplines, most notably: Human Behavioural Ecology (HBE), Evolutionary Psychology (EP) and studies of Cultural Evolution (CE). Multiple applications of evolutionary ideas to the human sciences are undoubtedly a good thing, demonstrating the usefulness of this approach to human affairs. Nevertheless, this fracture has been associated with considerable tension, a lack of integration, and sometimes outright conflict between researchers. In recent years however, there have been clear signs of hope that a synthesis of the human evolutionary behavioural sciences is underway. Here, we briefly review the history of the debate, both its theoretical and practical causes; then provide evidence that the field is currently becoming more integrated, as the traditional boundaries between sub-disciplines become blurred. This article constitutes the first paper under the new editorship of the Journal of Evolutionary Psychology, which aims to further this integration by explicitly providing a forum for integrated work.

The self-reported importance of olfaction during human mate choice

This study evaluated sex differences in the relative importance placed on olfactory cues during mate choice. To evaluate this, 151 men and 289 women completed an on-line version of the Romantic Interests Survey (RIS) (Herz & Inzlicht, 2002). Olfactory characteristics were declared to be extremely important during mate selection, more so than almost all other characteristics, but did not significantly differ between the sexes. There were significant differences concerning the odour source that individuals attend to, with greater preferences observed for a potential mates body odour as opposed to artificial fragrances they use. These findings suggest the body odour characteristics of a potential mate are perceived to be an important factor during mate choice.

Why does relative deprivation affect mental health? The role of justice, trust and social rank in psychological wellbeing and paranoid ideation

Purpose – Relative deprivation is associated with poor mental health but the mechanisms responsible have rarely been studied. The purpose of this paper is to hypothesize that childhood perceived relative deprivation (PRD) would be linked to sub-syndromal psychotic symptoms and poor wellbeing via beliefs about justice, trust and social rank. Design/methodology/approach – In total, 683 undergraduate students were administered measures of childhood PRD, hallucination-proneness, paranoia and wellbeing and measures of trust, social rank and beliefs about justice. A subsample supplied childhood address data. Multiple mediation analysis was used to assess pathways from childhood experiences to outcomes. Findings – Childhood PRD was associated with all three outcomes. The relationship between PRD and paranoia was fully mediated by perceptions that the world is unjust for the self and low social rank. The same variables mediated the relationship between PRD and poor wellbeing. There were no significant mediators o...

Patterns of physical and psychological development in future teenage mothers

The developmental patterns of teenage mothers are consistent with the idea that early childbearing is a component of an accelerated reproductive strategy induced by early-life conditions. The implications for interventions likely to affect the rate of teenage childbearing are discussed.

Suicide terrorism and post-mortem benefits

Lankford claims that suicide terrorists are suicidal, but that their suicidal tendencies are often frustrated by injunctive social norms. Martyrdom represents a solution, and terrorist organizations exploit this. In this commentary, we claim that this argument has not been fully made and that such ideation in itself does not explain a willingness to engage in punitive actions against an enemy. We suggest the psychology of kinship as a possible missing factor.