Local mating markets in humans and non-human animals

Local mating markets in humans and non-human animals. Ronald Noë. Behavioral Ecology and Sociobiology, October 2017, 71:148. https://doi.org/10.1007/s00265-017-2376-3

Abstract: In biology, the term ‘mating market’ has been fashionable for a few decades only, but sexual selection theory was implicitly based on economic principles from the start. I regard mating individuals explicitly as traders on markets and distinguish ‘global mating markets’, consisting of all reproducing members of a population, from ‘local mating markets’ (LMMs) that are disconnected in space and/or time. I focus on ways in which individuals make the best of variation among LMMs by adapting their mating strategy to each local market they enter. The ‘operational sex ratio’ (OSR; Emlen ST, Oring LW (1977) Science 197:215–223) gives a first approximation of the balance of power between the two trader classes: males and females ready to reproduce. The parameter I use is the local OSR (LOSR), the OSR of a single LMM. The balance of power is dependent not only on the LOSR, however, but also on the production costs and exchange values of ‘crucial commodities’, which often vary locally and over time. Distinguishing LMMs is most useful for species with strong variation in the LOSR. Human mating markets distorted by war, selective abortion and sex-biased migration are among the best-documented local markets with aberrant OSRs. Traders on LMMs may strategically adjust to supply and demand ratios and changes in their own market value but also attempt to change local market conditions or transfer to another local market with better conditions. Fine-tuning can result not only from conditional strategies, evolved under natural and sexual selection, but also from learning processes as far as species-specific cognitive constraints allow.

Significance statement: Biological market theory (BMT), which deals with cooperation among unrelated agents in general, is combined with sexual selection theory (SST), which deals with reproductive cooperation, to focus on an aspect that received little attention in the vast SST literature: adaptations that improve mating success when the market value of an individual varies considerably from one local mating market (LMM) to the next. An individual’s market value on an LMM is determined not only by the local operational sex ratio (LOSR) but also by the value of the goods and services that both sexes invest in their mates and/or the communal offspring. Case studies of both humans and non-human animals are used to illustrate the difference between global and local markets and to evaluate predictions based on the LMM-hypothesis.

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Prediction 2: sensitivity to one’s own market value and adjustment to changes in market value of self and others

...Broadly speaking, individual changes inmarket value can be due to changes relative to local competitors, changes in the LOSR, or changes in the production costs of commodities. As the consequences of the latter are hard to predict, I will concentrate on the other two factors, the first of which is notably well documented in humans. ***A universal, frequently reported human pattern is that men are attracted by youth in women and women are attracted by men that can offer resources***... During their exceptionally long mating career, men can gradually gain in value with age by slowly accumulating wealth or a steady rise in salary. Their market value can also increase abruptly, for example by high gains in the lottery, or a sudden ascent to a powerful position. ***After reaching maximal fertility in their early twenties (Hawkes and Smith 2010), women tend to gradually lose market value, as far as this is contingent on their age. Men are sensitive to cues informing about age, which is ultimately linked to reproductive potential***. Humans of either sex tend to adjust their demands and expectations to changes in their market value. For example, following earlier papers... in both methods and ideas, Pawłowski and Dunbar... showed that ***with increasing age, women become less demanding, quantified as the number of preferred characteristics listed in ‘Lonely Hearts’ advertisements. This sensitivity to market value of self in humans has since been confirmed in numerous other studies...  Climbing down a peg when one is not doing very well on the mating market, often is a ‘best-of-a-bad-job’ strategy***... Inferior competitors in several species use strategies radically different from those of their high-quality rivals. ***For example, big bullfrogs croak loudly in order to attract females, but small males of the same species remain silent and ambush the females that are on their way to the big bullies, a strategy known as ‘sneaking’...  Strategies that differ radically from the main stream exist among humanmales too, of course, e.g. rape and brothel visits.***

Members of several other species are also able to calibrate their mate preferences according to their own market value.  Spotted bowerbird males decorate their bowers with Solanum berries, the number of which shows considerable variation among males with higher numbers correlating with higher mating success. After experimental changes of the number of berries that decorated their bower, males added or removed berries to such an extent that the natural number was more or less restored. Males with berry-numbers considerably larger than what they had contributed themselves, suffered an increased risk of having their bowers disrupted by neighbouring males. - (Griggio and Hoi 2010). The latter authors also found indications of sensitivity to the own attractivity in bearded reedlings... Another house sparrow study (Schwagmeyer 2014) showed similar market effects, not only during pair formation at the start of the reproductive season but also in the form of partner switches during the season. ***The latter reminds of humans again: people report more satisfaction with their present partner when their prospects of switching to a higher quality mate are dim...***

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Check also: Behavioral display of lumbar curvature in response to the opposite sex. Zeynep Şenveli Bilkent University, Graduate Program in Neuroscience - Master's degree thesis. http://repository.bilkent.edu.tr/handle/11693/33362

And: The Reversed Gender Gap in Education and Assortative Mating in Europe. De Hauw, Yolien, Grow, Andre, and Van Bavel, Jan. European Journal of Population, https://link.springer.com/article/10.1007/s10680-016-9407-z

And: Marzoli, D., Havlícek, J. and Roberts, S. C. (2017), Human mating strategies: from past causes to present consequences. WIREs Cognitive Science, e1456. doi:10.1002/wcs.1456

And: The Causes and Consequences of Women’s Competitive Beautification. Danielle J. DelPriore, Marjorie L. Prokosch, and Sarah E. Hill. The Oxford Handbook of Women and Competition, edited by Maryanne L. Fisher. http://www.oxfordhandbooks.com/view/10.1093/oxfordhb/9780199376377.001.0001/oxfordhb-9780199376377-e-34