Life History Theory: An Overview

The evolution of life is the consequence of a process in which various forms compete to gather energy from their surroundings and transform it into copies of themselves. People "capture" energy from their surroundings (through foraging, hunting, or cultivation) and "allocate" it to reproduction and survival activities.

Selection rewards individuals that efficiently acquire and allocate energy to improve fitness within their biological niche. Energy does not come cheap. If people had limitless free energy, they could advance to the point where they could begin reproducing soon after birth, generate progeny, and preserve themselves so they never aged.

Individuals must, in biological fact, live within finite energy "budgets" (acquired via energy and time expenditures), never spending more than they have available. Allocating a constrained budget necessitates trade-offs, forcing judgments regarding the relative worth of various spending methods. Purchasing one expensive thing necessitates the sacrifice of others; spending now may result in less consumption later.

Life History Theory

The life history theory (LHT) presents an approach to tackle how entities must devote their resources and time to activities and features to maximize their viability amid trade-offs. LHT primarily focuses on the evolutionary dynamics that determine the scheduling of life occurrences about development, maturation, breeding, and aging since optimum allocations alter across the entire lifespan.

One of evolutionary psychology's main objectives is knowing the characteristics of psychological adjustments. LHT and evolutionary psychology are closely related for two reasons. First, psychological modifications represent a few of the investments humans have made throughout evolution, and they need much effort to build, maintain, and use. Since their development has been influenced by the same basic principles of selecting that LHT is concerned with, LHT can be used to successfully direct research into their origins, make-up, and mode of action.

Second, making the best choices about allocating time and effort to different daily responsibilities frequently necessitates processing detailed information about the surroundings. Some psychological modifications are built to deliver and respond to that information. LHT can once more serve as a framework for looking at the characteristics of these adjustments.

Trade-Offs Essential to Life History Theory

Two main strategies exist for improving fitness: investing in qualities that influence the age sequence of fatality or investing in features that influence the age timeframe of reproduction. Ultimately, longevity, fecundity, or both variations must mediate between characteristics and encompassing fitness. Due to allotment trade-offs, many, if not all, characteristics have conflicting effects on longevity and fertility, conflicting effects on an identical wellness element at two different times, or conflicting effects between a linked individual's sustenance and procreation and one's endurance element (e.g., own viability).

For instance −

  • An attribute that enhances fertility by boosting the number of matings (such as a mating display) may concurrently decrease longevity by impairing immune systems.

  • Energetic appropriations to expansion decrease fertility at early ages but boost fecundity at an advanced age.

  • Allotment to progeny viability (such as ingesting) decreases an individual's preservation or procreation.

  • The present-future reproductive trade-off, the quantity-quality of progeny trade-off, and the trade-off involving breeding labor and parental exertion are the three broad, basic trades that LHT uses to conceive specific allocation trade-offs.

Procreation in the Today and Tomorrow: The Trade-Off

An organism must choose at any time. Its energy is utilized in any ratio to produce offspring or to carry out existing tasks (such as growth, predator mitigation, maintenance, or extra energy harvesting). The potential price of not breeding today must be considered when allocating resources to prospective reproduction. Usually, reproducing today comes at the expense of raising the likelihood of not breeding later. Whatever allocation yields the highest level of inclusive fitness will be optimal.

Concerns with Senescence

The question of current versus prospective procreation was mainly used to explain why creatures were senesced in the early 1960s and 1950s. Because a more significant number of people are still living to witness its consequences, the selection is more outstanding on features exhibited at younger ages, according to Medawar. As deleterious mutations whose consequences manifest later in life accrue due to weaker selection against them, an organism's survival should tend to decline with age.

Williams expanded on this theory to include genes that have conflicting impacts on fitness at various ages, such as those that have a favorable impact on conception at an earlier age and a detrimental impact on longevity at a later age. Such genes with positive early-life benefits but negative later-life consequences should increase in communities.

Life History Theory Formulations

Despite assuming trade-offs, Williams and Hamilton were unconcerned with their effects. Gadgil and Bossert created the first contemporary LHT framework, and it conceptualized trade-offs as being inescapably required by non-renewable resource constraints. Organisms from their surroundings take up resources. Their capture velocity determines their energy expenditure. They have three options for "spending" funds at any one time.

By expanding, organisms will be able to capture more energy in the future, which will boost their fertility. Because of this, organisms usually go through an immature phase during which they are utterly incapable of reproducing till they attain a magnitude at which some investment in reproduction improves fitness rather than expansion. Organisms repair somatic tissue, devote energy to immunological function, increase energy generation, and other processes through maintenance.

Organisms replicate genes during reproduction. The life cycles of creatures are shaped by how they resolve this metabolic trade-off. The threefold trade-off involves present and potential procreation since upkeep and expansion influence fitness through their effects on subsequent breeding. The expense of reproduction is defined as the reduction in the likelihood of subsequent survivability, energy acquisition, and reproduction as a consequence of energy allotment to present reproduction.

By dividing into two halves, full replication at all intervals following the current one until death, and reproduction at the current timeframe, it is possible to analyze the present-future trade-off.

In principle, ideal life history programs maximize the energy budgets allotted to reproduction throughout life. Senescence is an unavoidable side effect of the architecture of optimal allocation. A bit further expenditure in equipe would be ineffective if upkeep were faultless and senescence had not happened because the maximum level would have been achieved.

Therefore at this time, some energy reallocation to procreation might benefit fitness. So, according to the disposable soma theory, it is always best for organisms to let the body decompose at a nonzero pace.

The advantage of dedicating assets and energy to the prospective decreases as the danger of death from difficult-to-avoid reasons like predators, catastrophes, and so forth rises since that effort is more specific to be "squandered." As a result, higher "exogenous" fatality risks induce senescence to occur more quickly. As a result, a large portion of LHT simulates life course endpoints due to age-specific exogenous mortality risk.

The Trade-Off between Progeny Quality and Number

The resource allocation to maximize offspring quantity against distribution to enhance progeny excellence is the subject of a second significant life cycle trade-off. Because parents only have a finite amount of resources to devote to reproduction, having more children must result in a lower aggregate amount per child. This trade-off is often quantified as several offspring vs. survival of offspring.

A straightforward model predicts that selection will modify expenditure per offspring to optimize offspring number above survival rate. When the advantages of expenditure, as is widely thought, decline with a degree of investment, the optimal point is attained when the proportionate drop of offspring produced matches the proportionate gain in offspring survivability to adulthood. As a result, the ideal investment is below what is needed for maximum survival. Also, the best investment for each child is agnostic of parental income.

Therefore, lifetime fertility equals the sum of resources divided by the amount invested for each child. More complex intergenerational models consider not just the survival of the kids but also their adult fitness, which might differ depending on their physical make-up, level of health, talents, and other factors gained because of parental care.

Life History Theory and Barter between Parental Care and Procreation

The trade-off between quantity and quality is complicated by sexual reproduction. Parents may make differential contributions to their kid's viability, even though offspring share nearly equal quantities of their parents' genetic material. Since each parent benefits from the expenditures made by the other parent and is motivated to allocate resources to create new offspring, children are a public good. There are interest clashes between the genders.

The divergent evolution of the sexes is a nearly universal result of sexual reproduction. Males suitable for mating can anticipate a reasonably high future reproduction rate, motivating them to participate in mating instead of parental care, especially when females are incredibly picky about mates due to increased initial investment in progeny. Because women do not choose them, males who may profit from parenthood do not get the opportunity.

Females may choose males for their readiness to engage in parenthood in particular situations—likely those where the benefit of biparental caregiving is significant—resulting in a smaller sex gap in allocation towards mating and parenting because of sexual clashes of purpose and mate rivalry, which economists call a "detrimental spillover," inefficient offspring production results.


From survival to procreation, our time and energy must be equitably or at the least rationally divided among them to lead a fruitful life and not be constrained or overpowered by just one motive. However, the way people do it and why they do it is an exciting turn of events.

Updated on: 11-Apr-2023


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