Mark Nelissen

Lineage based differences in grandparental investment: Evidence from a large British cohort study

Evolutionary theory suggests that maternal grandparents will invest more in their grandchildren than paternal grandparents, due to the difference between the certainty of maternity and the uncertainty of paternity. Most tests of this prediction have tended to use retrospective ratings by grandchildren rather than examining grandparental behaviour. Using a large-scale data set from the UK (n>7000), significant differences are shown between maternal and paternal grandparents in terms of frequencies of contact with their newborn grandchildren, while controlling for a wide range of other variables. Maternal grandparents also provided a significantly wider range of financial benefits than paternal grandparents. Maternal grandparents were also more likely to provide essentials and gifts and extras for the baby. Multiple correspondence analysis showed that contact frequencies systematically related to other measures of grandparental investment, indicating that contact frequencies are a useful proxy measure to examine overall investment. Findings are discussed with reference to the paternity uncertainty hypothesis.

CONTACT FREQUENCIES BETWEEN GRANDPARENTS AND GRANDCHILDREN IN A MODERN SOCIETY: ESTIMATES OF THE IMPACT OF PATERNITY UNCERTAINTY

Evolutionary theory suggests that maternal grandparents will invest more in their grandchildren than paternal grandparents, due to the difference between the certainty of maternity and the uncertainty of paternity. Tests of this prediction have tended to use retrospective ratings by grandchildren rather than self-reported behaviour by grandparents. Using a large-scale dataset from the Netherlands, we show significant differences between maternal and paternal grandparents in terms of frequencies of contact with their grandchildren, while controlling for a wide range of other variables. Our results show biases consistent with the paternity uncertainty hypothesis.

Maternal Grandmothers Do Go the Extra Mile: Factoring Distance and Lineage into Differential Contact with Grandchildren

Several studies conducted from an evolutionary perspective have documented differential investment in grandchildren by lineage. The majority of these studies have used retrospective ratings by grandchildren, but only a fraction of these studies have examined actual grandparental behavior. Here we focus on the interaction between distance and lineage on face-to-face contact with a (random) grandchild in a large scale sample. Our main prediction is that maternal grandparents are significantly more willing to travel in order to see their grandchild. While controlling for initiative of contact, urbanization, sex and age of the grandchild, educational attainment, marital status and age we found a significant interaction between distance and grandparent type on frequency of contact with a grandchild. Maternal grandmothers were significantly more inclined than paternal grandfathers and grandmothers to maintain frequent face-to-face contact, as distance between grandparent and grandchild increased. The results are discussed with reference to evolutionary theories of grandparental investment.

Celebrities: from teachers to friends: a test of two hypotheses on the adaptiveness of celebrity gossip

In this paper we present two compatible hypotheses to explain interest in celebrity gossip. The Learning Hypothesis explains interest in celebrity gossip as a by-product of an evolved mechanism useful for acquiring fitness-relevant survival information. The Parasocial Hypothesis sees celebrity gossip as a diversion of this mechanism, which leads individuals to misperceive celebrities as people who are part of their social network. Using two preliminary studies, we tested our predictions. In a survey with 838 respondents and in-depth interviews with 103 individuals, we investigated how interest in celebrity gossip was related to several dimensions of the participants’ social lives. In support of the Learning Hypothesis, age proved to be a strong predictor of interest in celebrities. In partial support of the Parasocial Hypothesis, media exposure, but not social isolation, was a strong predictor of interest in celebrities. The preliminary results support both theories, indicate that across our life span celebrities move from being teachers to being friends, and open up a list of future research opportunities.

Sound Production By Some Tanganyikan Cichlid Fishes and a Hypothesis for the Evolution of the r communication Mechanisnis

I. Sound production is studied in Halochromis murtoni, Simochromis diagramma, S. babatiltz, Tropheus moorii, T. brichardi and T. duboisi (Pisces, Cichlidae). The recorded sounds are analysed and visualized as sonograms. 2. As far as communication is concerned, Tropheus is specialized in sound production while Simochromis is specialized in colour patterns. 3. These ways of evolution from an Haplochromis-like ancestor could be correlated with the fact that Tropheus became night-active, and Simochromis day-active.

Sensory exploitation and cultural transmission: the late emergence of iconic representations in human evolution

Iconic representations (i.e., figurative imagery and realistic art) only started to appear consistently some 45,000 years ago, although humans have been anatomically modern since 200,000–160,000 years ago. What explains this? Some authors have suggested a neurocognitive change took place, leading to a creative explosion, although this has been contested. Here, we examine the hypothesis that demographic changes caused cultural “cumulative adaptive evolution” and as such the emergence of modern symbolic behavior. This approach usefully explains the evolution of utilitarian skills and tools, and the creation of symbols to identify groups. However, it does not equally effectively explain the evolution of behaviors that may not be directly adaptive, such as the production of iconic representations like figurines and rock art. In order to shed light on their emergence, we propose to combine the above-mentioned cultural hypothesis with the concept of sensory exploitation. The concept essentially states that behavioral traits (in this case iconic art production) which exploit pre-existing sensory sensitivities will evolve if not hindered by costs (i.e., natural selection). In this view, iconic art traditions are evolved by piggybacking on cumulative adaptive evolution. Since it is to date uncertain whether art has served any adaptive function in human evolution, parsimony demands paying more attention to the primary and afunctional mechanism of sensory exploitation as opposed to mechanisms of models based exclusively on secondary benefits (such as Miller’s, for instance, in which art is proposed to evolve as a sexual display of fitness).

Sensory Exploitation: Underestimated in the Evolution of Art As Once in Sexual Selection Theory?

In this chapter we argue that sensory exploitation, a model from sexual selection theory, deserves more attention in evolutionary thinking about art than it has received until now. We base our argument on the observation that in the past, sensory exploitation may have been underestimated in sexual selection theory, but that it is now winning field. Likewise, we expect that sensory exploitation can play a more substantial role in modeling the evolution of artistic behavior. Darwin’s theory of sexual selection provides a mechanistic basis to explain the evolution of male display traits. This mechanistic approach has proven useful to developing hypotheses about the evolution of human art. Both Boyd and Richerson (1985, ch. 8) and Miller (1998, 1999, 2000, 2001) have applied an indirect-benefit model from sexual selection to the evolution of artistic behavior. We argue that the mechanistic possibilities sensory exploitation has to offer as a model have remained underexplored so far, so we propose a concept based upon it. From the sensory exploitation perspective it follows that exploitation of pre-existing human perceptual and mental biases is a primary force in the evolution of artistic behavior (we stress that the use of a model from sexual selection does not imply art making evolved as a sexual display — we only use it for its mechanism) and that the indirect benefit model only provides secondary forces. Thus, sensory exploitation may operate alone under most conditions, and only sporadically secondary processes as a result of beneficial effects on individuals or groups are expected to kick in. The concept of sensory exploitation will need to play a central role in articulating all of the existing hypotheses about art.

A ‘gendered need’ explanation does not fully explain lineage based differences in grandparental investment found in a large British cohort study

Ghysels (2012) argues for a ‘gendered need’ explanation of lineage based differences in grandparental investment. Maternal grandmothers are subsidiary care-givers: only if mothers fail to fulfil this gender role, (maternal) grandmothers will step in. The SHARE data do indeed seem to support this explanation (though see Appendix). However, it is not at odds with an evolutionary explanation, such as paternity uncertainty theory. Paternity uncertainty theory suggests that matrilineal biases will emerge all else being equal (see Euler & Michalski, 2008, for review). If there are differences in need, then all else is not equal, and we should expect grandparents to respond accordingly.