Parental investment

parental careinvestmaternal carebiparental careParental investment in humansparental investment theoryParental effortbrood careintersexual parental investmentinvesting more in the relationship
Parental investment, in evolutionary biology and evolutionary psychology, is any parental expenditure (e.g. time, energy, resources) that benefits offspring.wikipedia
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Paternal care

paternal investmentMale parental carepaternal
Parental investment may be performed by both males and females (biparental care), females alone (exclusive maternal care) or males alone (exclusive paternal care).
In biology, paternal care is parental investment provided by a male to his own offspring.

Evolutionary psychology

evolutionary psychologistevolutionary psychologistsevolutionary
Parental investment, in evolutionary biology and evolutionary psychology, is any parental expenditure (e.g. time, energy, resources) that benefits offspring.
There have been studies of human social behaviour related to infanticide, intelligence, marriage patterns, promiscuity, perception of beauty, bride price, and parental investment, with impressive findings.

Mate choice

mate selectionfemale choicemate preference
This theory has been influential in explaining sex differences in sexual selection and mate preferences, throughout the animal kingdom and in humans.
In 1972, soon after Williams' revival of the subject, Robert L. Trivers presented his parental investment theory.

Life history theory

life historylife historieslife-history
Parental investment theory is a branch of life history theory.
A life history strategy is the "age- and stage-specific patterns" and timing of events that make up an organism's life, such as birth, weaning, maturation, death, etc. These events, notably juvenile development, age of sexual maturity, first reproduction, number of offspring and level of parental investment, senescence and death, depend on the physical and ecological environment of the organism.

Robert Trivers

TriversR. L. TriversTrivers, R. L.
Parental investment theory, a term coined by Robert Trivers in 1972, predicts that the sex that invests more in its offspring will be more selective when choosing a mate, and the less-investing sex will have intra-sexual competition for access to mates. Robert Trivers' theory of parental investment predicts that the sex making the largest investment in lactation, nurturing, and protecting offspring will be more discriminating in mating; and that the sex that invests less in offspring will compete via intrasexual selection for access to the higher-investing sex (see Bateman's principle ).
Trivers proposed the theories of reciprocal altruism (1971), parental investment (1972), facultative sex ratio determination (1973), and parent–offspring conflict (1974).

Fisher's principle

Fisher's theoryFisher's prediction of a 1:1 male to female sex ratioFisher's theory of sex ratio selection
In 1930, Ronald Fisher wrote The Genetical Theory of Natural Selection, in which he introduced the modern concept of parental investment, introduced the sexy son hypothesis, and introduced Fisher's principle.
Fisher couched his argument in terms of parental expenditure, and predicted that parental expenditure on both sexes should be equal.

Reproductive success

passing ofreproductive assurancereproductive outcomes
They increase their own reproductive success through feeding the offspring in relation to their own access to the female throughout the mating period, which is generally a good predictor of paternity.
Parental investment is a key factor in reproductive success since taking better care to offspring is what often will give them a fitness advantage later in life.

Natural selection

selectionselectiveselected
This introduced the concept of natural selection to the world, as well as related theories such as sexual selection.
In contrast, K-selected species are strong competitors in crowded niches, and invest more heavily in much fewer offspring, each with a relatively high probability of surviving to adulthood.

The Genetical Theory of Natural Selection

In 1930, Ronald Fisher wrote The Genetical Theory of Natural Selection, in which he introduced the modern concept of parental investment, introduced the sexy son hypothesis, and introduced Fisher's principle.
Other chapters discuss parental investment, Fisher's geometric model, concerning how spontaneous mutations affect biological fitness, Fisher's principle which explains why the sex ratio between males and females is almost always 1:1, reproductive value, examining the demography of having girl children.

Parent–offspring conflict

parent-offspring conflictParent offspring conflictgenomic conflict
These differences may lead to parent-offspring conflict.
It is used to describe the evolutionary conflict arising from differences in optimal parental investment (PI) in an offspring from the standpoint of the parent and the offspring.

Ronald Fisher

R.A. FisherR. A. FisherFisher
In 1930, Ronald Fisher wrote The Genetical Theory of Natural Selection, in which he introduced the modern concept of parental investment, introduced the sexy son hypothesis, and introduced Fisher's principle.

Offspring

broodprogenybroods
Parental investment, in evolutionary biology and evolutionary psychology, is any parental expenditure (e.g. time, energy, resources) that benefits offspring.

Cuckold

cuckoldrycuckoldingcuckolded
PIT explains this, as woman's sexual infidelity decreases the male's paternal certainty, thus he will show more stress due to fear of cuckoldry.
In evolutionary biology, the term is also applied to males who are unwittingly investing parental effort in offspring that are not genetically their own.

Sexual jealousy

Sexual jealousy in humansjealous and possessive
PIT (Parental Investment Theory) also explains patterns of sexual jealousy.
Psychologists have found that males react very strongly to sexual infidelity, whereas females are more likely to forgive a one-time sexual adventure if it does not threaten the male parental investment.

Ophioblennius atlanticus

redlip blenniesredlip blennyBlennophis webbii
This indiscriminative parental care by males is also observed in redlip blennies.
Allopaternal care seems to be a huge disadvantage from an evolutionary perspective, since the male expends its resources to benefit genetically unrelated offspring.

Parent

parentspaternitybiological parent
They increase their own reproductive success through feeding the offspring in relation to their own access to the female throughout the mating period, which is generally a good predictor of paternity.
While parents tend to maximize the number of offspring, the offspring can increase their fitness by getting a greater share of parental investment often by competing with their siblings.

Sociality

gregarioussocial animalsolitary
The human need to have a birth attendant also requires sociality.
This wasp behaviour evidences the most fundamental characteristic of animal sociality: parental investment.

Tropheus moorii

T. moorii
For example, in the cichlid fish Tropheus moorii, a female has very high parental investment in her young because she mouthbroods the young and while mouthbrooding, all nourishment she takes in goes to feed the young and she effectively starves herself.
T. moorii females have unusually high parental investment in their offspring since they produce large eggs and buccally feed their young.

Mate desertion

These trade-offs between costs and benefits are further reflected in the two major conflicts driving mate desertion: 1) parent-offspring conflict over the level of parental investment that a parent should provide and 2) sexual conflict between mates over who should provide care and how much care should be provided.

R/K selection theory

K-selectedr-selectedr-strategists
The focus on either an increased quantity of offspring at the expense of individual parental investment of r-strategists, or on a reduced quantity of offspring with a corresponding increased parental investment of K-strategists, varies widely, seemingly to promote success in particular environments.

Jealousy

jealousjealousiesJealousy definitions
It has been argued that jealousy has developed to avert the risk of potential loss of parental investment in offspring.
According to the Parental Investment Model based on parental investment theory, more men than women ratify sex differences in jealousy.

Cinderella effect

mistreated the twins
Evolutionary psychologists Martin Daly and Margo Wilson propose that the Cinderella effect is a direct consequence of the modern evolutionary theory of inclusive fitness, especially parental investment theory.

Crested auklet

crestedAethia cristatellaCrested auklet (''Aethia cristatella'')
An example of this is seen in crested auklets, where parents share equal responsibility in incubating their single egg and raising the chick.
Since both sexes are ornamented, crested auklets align with Robert Trivers's parental investment theory, which predicts that with biparental care, mutual choosiness will arise.

Bateman's principle

Robert Trivers' theory of parental investment predicts that the sex making the largest investment in lactation, nurturing, and protecting offspring will be more discriminating in mating; and that the sex that invests less in offspring will compete via intrasexual selection for access to the higher-investing sex (see Bateman's principle ).
Consequently, reversals in sex roles and reproductive variance are consistent with Bateman's principle, and with Robert Trivers's parental investment theory.

Parental care in birds

birdsparental careparents help
Parental investment is any form of investment made by a parent that increases an offspring's rate of survival (reproductive success) at the expense of the parent or parent's ability to divert investment towards a new brood.