Motivation and emotion/Book/2023/Life history theory and human reproductive strategies

Life history theory and human reproductive strategies:
How does life history theory explain human reproductive strategy?

Overview

Case study

Life as we know it is very different to the lives of our ancestors. If you're reading this you exist, and if you exist it is because your parents exist - this cycle can continue for some time. However, the further up you go, the more relevant life history theory becomes. For you and I to exist our ancestors would have had to make very specific decisions at very specific times in order to ensure their survival, their reproductive success, and the survival of their offspring. This process can be thoroughly understood by applying LHT to the evolution of our species. In order to understand the reproductive strategies of our species across evolution through the lens of LHT, one must first garner a sufficient understanding of LHT alone, as well an understanding of reproductive strategies independent of LHT. The purpose of this page is to provide a comprehensive chapter on life history theory (LHT) and how it can be used to explain human reproductive strategies.

Focus questions: What is life history theory? Define the different types of human reproductive strategies. How does life history theory explain these human reproductive strategies?

What is life history theory?

Life history theory

Life history theory is an evolutionary framework which posits that the natural albeit limited resources vital to self-preservation and reproduction are applied according to different strategies which are developed and utilised depending on the individuals current stage of life and specific adaptive requirements - ultimately for the purpose of both survival, and the propagation of the organisms genetics (Csathó & Birkás, 2018). How and when these resources are applied depends on what life history strategy the individual is using. Life history strategy is therefore specific to what stage the individual is in relative to survival, including birth, maturation, and death (Reynolds & McCrea, 2016). Life history contingencies is essentially the state of the environment which determines the evolution, development, and implementation of different reproductive strategies (Reynolds & McCrea, 2016). These environmental factors include harshness (such as the mortality and morbidity rates that vary by age), unpredictable harshness (such as the consistency of harshness over time), and resource scarcity (such as the availability of energy resources and the intensity of competition for these resources (Griskevicius et al, 2011)).

Fast life history strategies, characterised by early maturation, a greater number of sexual partners to whom one is less committed, and less parenting of offspring, are often produced by unpredictable and severe environments. Unpredictability and harshness have an impact on dispositional social and emotional functioning as well as the emergence of personality traits that are more likely to lead to unstable social connections or self-centered behaviour (Csathó & Birkás, 2018).

In contrast, a slower life history strategy typically emerges in an environment with plentiful resources, predictability, and little risk to life. People that adopt a slower life history strategy typically develop more slowly, mature later, and are more focused on the future (Kavanagh & Kahl (2018). Humans have a significant amount of within-species variety despite being a species with a sluggish approach. It is significant to remember that neither quick nor slow tactics are intrinsically superior; rather, the advantages of each strategy depend on the circumstances surrounding the individual. Essentially, the harder ones life, or the closer to danger and therefore death one is, the faster their life history strategy.

The age at which people have children in a given county is inversely correlated with the county's violent crime statistics. Reproductive timing is explicitly connected to violent crime—the sort of crime that is linked to local mortality risks—rather than just varying as a function of SES or of crime in general. People appear to adopt faster life cycle strategies commensurate with earlier ages of reproduction in response to both persistent mortality cues and chronic resource scarcity. Simply put, the more mortally threatening an area or environment, the faster life history strategy is adopted by the inhabitants of said environment (Griskevicius et al, 2011).

Figure 1. Classic depiction of human evolution. Each stage represents evolutionary variation.

Natural selection

Natural selection is an evolutionary mechanism which states that living organisms which are more adaptable than others are more likely to pass on their genes and therefore their superior adaptive ability, which causes the species to fundamentally change over time (Barton & Partridge, 2000). Natural selection is described by Charles Darwin as a force against natural destruction and extinction; because desirable traits are chosen and passed down over generations, species become fully adapted to their surroundings, reducing the chance of destruction by nature. Instead of a battle for survival with extinction as the goal, natural selection provides a beneficial and thus positive outcome—the perfect adaptation of a species to its environment (Darwin, 1859).

Certain principles of life history theory are interchangeable with Darwinian theory, with an emphasis on natural selection (Bolger, 2012). Charles Darwin, in his book On the Origin of Species, briefly described the idea of sexual selection, which is another aspect of species development, in addition to the idea of natural selection. Male individuals with traits that enable them to successfully attract females are more likely to procreate and consequently generate more children than other male individuals since producing progeny is essential to a species' existence (Darwin, 1859). Additionally, there are variations of these favourable sexual traits that would be handed down to offspring.

Darwin describes numerous strategies used by male birds to entice females in The Origin of Species, including singing to prospective partners, flaunting a variety of vividly coloured feathers, and engaging in attention-grabbing behaviours. If any change in these traits made male birds more likely to mate, that change would probably be passed down to the children and eventually take over the population in succeeding generations. Variations of this kind, like colour, singing ability, or ornamentation, may not directly affect an organism's capacity to survive in nature; rather, the utility of the variations in aiding reproduction is what enables them to be chosen and maintained within a species; these variations and their primary utility towards reproductive success can be anagolized with life history theory and specifically life history strategies, albeit very particular situational varieties which are becoming more prevalent in humans as time progresses (Darwin, 1859). (Due to first world comfort, certain anachronistic reproductive value is being superseded by specific, nuanced forms of reproductive strategy - due to a slower life history strategy).

Evolutionary reproductive strategies

Long-term strategy

Monogamy

Natural selection is the practice of having one mate exclusively (Buss, 2005). Humans also have a variety of neurophysiological attachment mechanisms associated to pair bonding and monogamy across species (Buss, 2005). Only a small percentage of men in communities that practise polygyny have more than one wife, making monogamy the most common type of union globally. A different distribution can be shown for covert enduring connections. Men who are monogamously paired may form long-term relationships with other women (covert polygyny), while women who are monogamously paired may have many long-term relationships (covert polyandry). There are also covert monogamous unions, for instance when they are deemed illegal for a number of reasons.

Polygyny

Individual men who can mate with multiple females use polygynous mating methods, whereas females typically only mate with one male (Buss, 2005). Polygyny is by far the most prevalent "default" mating system among mammals as a whole, possibly in part because female animals have evolved specific nutritional care for infants; in many mammals, females and their offspring represent an independent ecological unit. In these circumstances, males focus on mating effort while females focus on parenting effort. Even in countries that are regarded as egalitarian, polygyny is often connected in some way to men's status or accomplishments (Buss, 2005).

Polygyny

Short-term strategy

When females mate with many males and males mate with many females, it is known as a short-term mating strategy or a multimale-multifemale strategy. Short-term reproductive strategies are generally characterised by low-commitment and prioritisation of the quantity of partners rather than quality (Buss & Schmitt, 2017). These relationships are typically short-lived, lack the exclusivity of monogamous or polygynous partnerships, and place the majority of the long-term parenting responsibilities on the female and her family. Numerous short-term sexual behaviours, such as premarital sex, extramarital sex, and mate poaching (attracting someone who is already in a relationship (Buss, 2007)), are common throughout most cultures, according to ethnological research (Buss, 2005). Short-term mating allows women to acquire resources right away, ensure a kid if a long-term partner is infertile, and have access to a man's superior genes who she would not be allowed to marry (Buss, 2005).

The good genes hypothesis

The good genes theory has received the majority of attention when discussing the potential roles that women's short-term mating may play. According to this theory, short-term mating can help women by giving them access to men who have particularly good genes that would otherwise not be as available through long-term mating (Buss & Schmitt, 2019). There is an indication that women favour various traits in short-term relationships; some of these traits may be the result of sexual selection of advantageous genes (Buss & Schmitt, 2019). For instance, when evaluating men for one-night stands vs marriage partners, women often give more weight to a man's physical beauty, and when it comes to short-term relationships more often than not, women prefer a man with a manly face.

Mate switching hypothesis

The mate switching hypothesis has different forms: one entails preparing a backup partner in case something happens to a woman's primary partnership, such as a spouse getting hurt or dying in combat, or simply in cynical expectation of a possible split. It's been referred to as the "mate insurance function." Another entails engaging in a brief sexual encounter to make dumping a current partner simpler. A third option entails moving up to a spouse who has a better mate value or who provides more advantages and fewer disadvantages than the one one is now with. A fourth variation entails using short-term mating to gauge one's mate value and determine whether there might be more appealing and approachable potential partners available in the mating market.

Life history theory and human reproductive strategy

How does life history theory explain human reproductive strategies?

Monogamy

Humans experience slower development of offsprings and significant dependability on parental protection (in order to ensure genetic propagation), which are aspects associated with slow life history strategies. In turn, slow life history strategies are associated with monogamy. According to Buss (2005), the majority of divorces take place between the fourth and the sixth year of marriage, and men who engage in serial monogamy have better reproductive outcomes and therefore genetic propagation than those who remain committed to a single woman for the rest of their lives. However, repeated mating does not give women a reproductive advantage over other women, rendering resource allocation for the purpose of repeated mating counterproductive. Lower rates of human offspring survival are caused by partner abandonment, thus alluding to a preferable monogamous arrangement for the sake of offspring survival and therefore genetic influence and propagation (Buss, 2005).

Polgyny

When a guy can regularly command and protect food supply, territories, or other resources, resource-defence polygyny develops. Despite the fact that he is already mated, females preferentially desire and seek mate-ships with this high-resource male; this is, according to life history theory, so that the female has the highest chances of survival. The polygyny threshold model states that females are more likely to mate several times when the benefits outweigh the costs of doing so; for instance sharing a male's resources and engaging in competition with other females and their offspring. Women prefer to mate with wealthy, high-status men rather than poor, low-status men who would be incapable of supporting a family (Borgerhoff-Mulder, 1992), and polygyny is more likely to develop in environments where the genetic quality of men is valued, such as dangerous environmental contingencies, as well as when ecologically adaptive in a other instances (Buss, 2005); by securing a male who can support her family, the female has employed her resources, whether it be her beauty or other resources, as a means to secure the male she desires, predominantly for her survival and for the survival of her offspring, as per life history theory.

Men may advocate equitable resource distribution as a strategy of securing many partners in addition to status-related resources. The acquisition of multiple wives greatly increases the reproductive success of men and therefore natural selection would have favoured men who preferred a large number of mating partners. Buss (2005) also implies that men who are dominating and, when possible, amass the most resources can use their resources to gain marriages to multiple women, which ensures his genetic proliferation. By allocating his resources to obtain as many females as possible, the male has successfully succeeded in propagating his genes. Due to humans predominantly employing a slow life history strategy because of the slow physical maturation of humans, it is in the males best interest to not abandon his offsprings for the purpose of defending them so his genetics can prevail. Men may also engage polygynous structure depending on how high mortality rates are in the specific region (Ember, 2007). The higher the mortality rates, the more polygyny is practiced (Ember, 2007) - this encourages men to "secure" their genetic propagation before likely death. This is especially prevalent during war (Ember, 2007).

Identifying Women of High Reproductive Value Features of physical appearance and apparent behaviour were the two main sets of observable cues that were probabilistically connected with reproductive value in our ancestors. Those cues linked to relative youth make up one group of cues. Life history theory states that individuals do their best to achieve genetic immortality; given that she has many more years to reproduce in the future, a young adult female has higher reproductive value than any other older adult female, as she is the most fertile and provides the male with the best opportunity for genetic influence. This reasoning generates a compelling range of precise predictions as well as an evolutionary, life history-based explanation of feminine attractiveness to men.

Historical applications

Although humans almost universally employ slow life history strategies in comparison to other species' regardless of the chronological setting, it is reasonable to assume that the further back in history one travels, the faster the strategy (without officially employing a fast strategy). Our ancestors were more inclined to practice polygyny due to the dangerous environmental contingencies and high chance of spouse or offspring death - this prompted a faster life history strategy so as to secure as many children and therefore grandchildren a possible; this was particularly more important to our male ancestors (Chapais, 2013).

Modern applications

Social darwinism

Social darwinism is the application of the theories and ideas of natural selection to aspects of human life. Instead of adaptability, survival, and continuation of genetic legacy being the end goal for organisms according to natural selection - power, both politically and financially are a result of natural selection in the modern age (Halliday, 1971). Simply, those with superior genes will naturally obtain more power and status than those whose genes are inferior - this allows those with more status and power better means to produce more offspring than those who are not. For example, the contrast between an accomplished, affluent individual and a poor, unskilled individual, according to social darwinism, are likely a testament to the first individuals superior genetics (Halliday, 1971). Women tend to be attracted to men with more resources; in the modern age, these resources are status, money, and power. Therefore, according to social darwinism, women are more drawn to men who have these resources because it is an indication of their superior genes - which they can then secure for their offspring - in accordance with life history theory. For men, however, this is likely to be same as ever before - judging the reproductive value of females on their beauty and fertility.

Quiz 1 Life history contingencies are? The state of the environment which determines the evolution, development, and implementation of different reproductive strategies The state of the individual which determines the feasibility, planning, and implementation of different reproductive strategies 2 Polygyny is? Multiple females to a male Multiple males to a female 3 Fast life history strategies are associated with? More dangerous environments Less dangerous environments 4 Humans exhibit patterns more heavily associated with? Slow life-history strategies Fast life-history strategies

Conclusion

Life history theory posits that organisms, including humans, direct and spend our limited resources - which differ depending on gender - in particular ways for the purpose of self-survival, reproductive success, and offspring survival. Natural selection is essentially the by product or result of this resource spending. The better one spends and the more successful their endeavour, the more likely their genetics are adaptively superior, rendering them a higher chance of achieving this reproductive success, leading to the proliferation of these superior genetics.

There are both long-term and short-term reproductive strategies which have been employed by humans throughout history all the way up to today. The two most prevalent long-term strategies are polygyny and monogamy. In order for a male to successfully lead a polygynous reproductive strategy, he must be in abundance of resources. Humans have been shown to possess a variety of intrinsic mechanisms in line with pair bonding and monogamous practice. The short-term reproductive strategy is abundant mating between both genders. The two best explanations for this are the mate switching hypothesis and the good genes hypothesis; which states that women seek men based purely on the resources they possess, which would otherwise be unobtainable via a long-term strategy. The mate-switching hypothesis is essentially a multi-variant hypothesis which lists four reasons for short-term actions, such as "mate-insurance" in case of partner death, and for the purpose of securing genetics from one who is superior than the current mate.

Life history theory can be used to understand the several reproductive strategies used in the past and in the present. Ones limited resources are applied according to either a fast or slow life history theory. Life history explains monogamous strategy as the motivation to propagate ones genes by allocating ones resources to the needed protection of ones offspring through the prevention of partner abandonment (which would likely end in offspring death). Polygyny can be explained using life history theory as desire to create as many progenies as possible for genetic influence; for women, it is primarily to secure the best genes from the most competent male, as well as securing resources for themselves and their offspring. The further you regress in history, the more viable fast-slow strategies would be. Modern day female reproductive strategies can be attributed to securing the genetics (physically and intellectually) of the best males, which today is measured by resources like money - and remains largely the same for men.

See also

Darwinism (Wikipedia)

Evolutionary fitness (Wikipedia)

Evolutionary psychology (Wikipedia)

Human behavioural ecology (Wikipedia)

Human reproductive strategies

Life history theory

Mate-seeking behaviour (Wikiversity, Book chapter, 2010)

References

Barton, N., & Partridge, L. (2000). Limits to natural selection. BioEssays, 22(12), 1075–1084.

Bolger, D. (Ed.). (2012). A companion to gender prehistory. John Wiley & Sons.

Buss, D. M. (2007). The evolution of human mating. Acta Psychologica Sinica, 39(3), 502-512.

Buss, D. M. (Ed.). (2005). The handbook of evolutionary psychology. John Wiley & Sons.

Buss, D. M., & Schmitt, D. P. (2019). Mate preferences and their behavioral manifestations. Annual review of psychology, 70, 77-110.

Buss, D. M., & Schmitt, D. P. (2017). Sexual strategies theory: An evolutionary perspective on human mating. In Interpersonal Development (pp. 297–325). Routledge.

Chapais, B. (2013). Monogamy, strongly bonded groups, and the evolution of human social structure. Evolutionary Anthropology: Issues, News, and Reviews, 22(2), 52-65.

Csathó, Á., & Birkás, B. (2018). Early-life stressors, personality development, and fast life strategies: An evolutionary perspective on malevolent personality features. Frontiers in psychology, 9, 305.

Darwin, C. (2016). On the origin of species, 1859.

Ember, M., Ember, C. R., & Low, B. S. (2007). Comparing explanations of polygyny. Cross-Cultural Research, 41(4), 428-440.

Griskevicius, V., Delton, A. W., Robertson, T. E., & Tybur, J. M. (2011). Environmental contingency in life history strategies: the influence of mortality and socioeconomic status on reproductive timing. Journal of personality and social psychology, 100(2), 241.

Halliday, R. J. (1971). Social Darwinism: a definition. Victorian Studies, 14(4), 389-405.

Kavanagh, P. S., & Kahl, B. L. (2018). Are expectations the missing link between life history strategies and psychopathology?. Frontiers in Psychology, 9, 89.

Mulder, M. B. (1992). Women’s strategies in polygynous marriage: Kipsigis, Datoga, and other East African cases. Human Nature, 3, 45–70.

Orr, H. A. (2009). Fitness and its role in evolutionary genetics. Nature Reviews Genetics, 10(8), 531–539.

Reiss, S. (2012). Intrinsic and extrinsic motivation. Teaching of psychology, 39(2), 152–156.

Reynolds, J. J., & McCrea, S. M. (2016). Life history theory and exploitative strategies. Evolutionary Psychology, 14(3), 1474704916659483.

External Links

Evolution (Encyclopedia Britannica)

Motivation (Encyclopedia Britannica)

Asexual and sexual reproduction