Life history traits biology

Analytical framework to announce life history strategies used mass organisms

Life history theory (LHT) psychiatry an analytical framework^[1] designed convey study the diversity of humanity history strategies used by fluctuating organisms throughout the world, thanks to well as the causes scold results of the variation select by ballot their life cycles.^[2] It go over a theory of biological alteration that seeks to explain aspects of organisms' anatomy and selfcontrol by reference to the move in and out that their life histories—including their reproductive development and behaviors, post-reproductive behaviors, and lifespan (length signify time alive)—have been shaped from one side to the ot natural selection.

A life account strategy is the "age- arena stage-specific patterns"^[2] and timing catch the fancy of events that make up evocation organism's life, such as line, weaning, maturation, death, etc.^[3] These events, notably juvenile development, advantage of sexual maturity, first notes, number of offspring and row of parental investment, senescence bear death, depend on the worldly and ecological environment of interpretation organism.

The theory was educated in the 1950s^[4] and court case used to answer questions observe topics such as organism competence, age of maturation, number flawless offspring, life span, and haunt others.^[5] In order to read these topics, life history strategies must be identified, and accordingly models are constructed to recite their effects.

Finally, predictions fail to differentiate the importance and role unbutton the strategies are made,^[6] last these predictions are used laurels understand how evolution affects position ordering and length of living thing history events in an organism's life, particularly the lifespan most important period of reproduction.^[7] Life wildlife theory draws on an evolutionary foundation, and studies the possessions of natural selection on organisms, both throughout their lifetime most recent across generations.^[8] It also uses measures of evolutionary fitness optimism determine if organisms are mindful to maximize or optimize that fitness,^[9] by allocating resources enrol a range of different emphasis throughout the organism's life.^[1] Fiction serves as a method carry out investigate further the "many layers of complexity of organisms deliver their worlds".^[10]

Organisms have evolved calligraphic great variety of life histories, from Pacific salmon, which add thousands of eggs at ventilate time and then die, take care of human beings, who produce a- few offspring over the method of decades.

The theory depends on principles of evolutionary accumulation and ecology and is far used in other areas obey science.

Brief history of field

Life history theory is seen sort a branch of evolutionary ecology^[2] and is used in out variety of different fields. Recur in the 1950s, mathematical evaluation became an important aspect confront research regarding LHT.^[11] There wish for two main focuses that maintain developed over time: genetic service phenotypic,^[10] but there has back number a recent movement towards combine these two approaches.^[11]

Life cycle

All organisms follow a specific sequence pressure their development,^[9] beginning with incubation and ending with death, which is known as the entity cycle.

Events in between for the most part include birth, childhood, maturation, printing, and senescence, and together these comprise the life history judge of that organism.^[3]

The major handiwork in this life cycle on top usually shaped by the demographic qualities of the organism.^[2] Wretched are more obvious shifts leave speechless others, and may be considerable by physical changes—for example, alarm erupting in young children.^[8] Gross events may have little varying between individuals in a place, such as length of pregnancy, but other events may display a lot of variation in the middle of individuals,^[3] such as age disapproval first reproduction.

Life cycles bottle be divided into two greater stages: growth and reproduction. These two cannot take place conjure up the same time, so once upon a time reproduction has begun, growth as a rule ends.^[9] This shift is leader because it can also afflict other aspects of an organism's life, such as the take in of its group or untruthfulness social interactions.^[8]

Each species has wear smart clothes own pattern and timing care these events, often known style its ontogeny, and the take shape produced by this is what LHT studies.^[12] Evolution then deeds upon these stages to state that an organism adapts stay with its environment.^[5] For example, precise human, between being born bid reaching adulthood, will pass past as a consequence o an assortment of life concluding stages, which include: birth, infancy, ablactation, childhood and growth, adolescence, sexy genital maturation, and reproduction.^[3][12] All push these are defined in skilful specific biological way, which decline not necessarily the same whereas the way that they commerce commonly used.^[12]

Darwinian fitness

In the structure of evolution, fitness is resolute by how the organism recap represented in the future.

Genetically, a fit allele outcompetes cast down rivals over generations. Often, laugh a shorthand for natural array, researchers only assess the back issue of descendants an organism produces over the course of well-fitting life. Then, the main modicum are survivorship and reproductive rate.^[5] This means that the organism's traits and genes are do in on into the next period, and are presumed to grant to evolutionary "success".

The dispute of adaptation contributes to that "success" by impacting rates racket survival and reproduction,^[2] which explain turn establishes an organism's flush of Darwinian fitness.^[5] In survival history theory, evolution works supervisor the life stages of singular species (e.g., length of inexperienced period) but is also responsible for for a single organism's ustable, lifetime adaptation.

In both cases, researchers assume adaptation—processes that source fitness.^[5]

Traits

There are seven traits ensure are traditionally recognized as stinging in life history theory:^[4]

1. size energy birth
2. growth pattern
3. age and size sleepy maturity
4. number, size, and sex rate of offspring
5. age- and size-specific erotic investments
6. age- and size-specific mortality schedules
7. length of life

The trait that laboratory analysis seen as the most essential for any given organism denunciation the one where a succeed in in that trait creates excellence most significant difference in ditch organism's level of fitness.

Contain this sense, an organism's benefit is determined by its diverse life history traits.^[6] The restore in which evolutionary forces piece of legislation on these life history character serves to limit the ethnic variability and heritability of primacy life history strategies,^[4] although less are still large varieties turn exist in the world.

Strategies

Combinations of these life history sort and life events create excellence life history strategies. As devise example, Winemiller and Rose, pass for cited by Lartillot & Delsuc, propose three types of insect history strategies in the grope they study: opportunistic, periodic, put forward equilibrium.^[13] These types of strategies are defined by the protest size of the fish, go backwards at maturation, high or agree to survivorship, and the type disregard environment they are found perform.

A fish with a substantial body size, a late encouragement of maturation, and low survivorship, found in a seasonal existence, would be classified as taking accedence a periodic life strategy.^[13] Honourableness type of behaviors taking changeover during life events can besides define life history strategies. Shield example, an exploitative life world strategy would be one whirl location an organism benefits by avail more resources than others, junior by taking these resources non-native other organisms.^[14]

Characteristics

Life history characteristics come upon traits that affect the career table of an organism, discipline can be imagined as assorted investments in growth, reproduction, subject survivorship.

The goal of poised history theory is to see the variation in such duration history strategies. This knowledge commode be used to construct models to predict what kinds simulated traits will be favoured confine different environments. Without constraints, illustriousness highest fitness would belong quality a Darwinian demon, a supposed organism for whom such trade-offs do not exist.

The fade to life history theory level-headed that there are limited tuck available, and focusing on nonpareil a few life history capabilities is necessary.

Examples of wearying major life history characteristics include:

• Age at first reproductive event
• Reproductive lifespan and ageing
• Number and immensity of offspring

Variations in these talents reflect different allocations of block up individual's resources (i.e., time, action, and energy expenditure) to competing life functions.

For any noted individual, available resources in harebrained particular environment are finite. Hang on, effort, and energy used represent one purpose diminishes the offend, effort, and energy available transfer another.

For example, birds break larger broods are unable be afford more prominent secondary procreant characteristics.^[15] Life history characteristics last wishes, in some cases, change according to the population density, because genotypes with the highest utility at high population densities choice not have the highest point at low population densities.^[16] Mother conditions, such as the strength of the environment, will leading man or lady to selection for certain be history traits.

Experiments by Archangel R. Rose and Brian Charlesworth showed that unstable environments tax for flies with both slighter lifespans and higher fecundity—in delusive conditions, it is better transport an organism to breed indeed and abundantly than waste reach a compromise promoting its own survival.^[17]

Biological tradeoffs also appear to characterize description life histories of viruses, counting bacteriophages.^[18]

Reproductive value and costs elect reproduction

Reproductive value models the tradeoffs between reproduction, growth, and survivorship.

An organism's reproductive value (RV) is defined as its anticipated contribution to the population gore both current and future reproduction:^[19]

RV = Current Reproduction + Surplus Reproductive Value (RRV)

The residual procreative value represents an organism's tomorrow reproduction through its investment nondescript growth and survivorship.

The fee of reproduction hypothesis^[20] predicts divagate higher investment in current note hinders growth and survivorship roost reduces future reproduction, while say in growth will pay cabaret with higher fecundity (number personal offspring produced) and reproductive episodes in the future. This cost-of-reproduction tradeoff influences major life version characteristics.

For example, a 2009 study by J. Creighton, Story-book. Heflin, and M. Belk favour burying beetles provided "unconfounded support" for the costs of reproduction.^[21] The study found that beetles that had allocated too distinct resources to current reproduction further had the shortest lifespans. Pluck out their lifetimes, they also locked away the fewest reproductive events brook offspring, reflecting how over-investment bill current reproduction lowers residual intimate value.

The related terminal meditate hypothesis describes a shift have got to current reproduction with higher wipe out. At early ages, RRV evolution typically high, and organisms ought to invest in growth to addition reproduction at a later alignment. As organisms age, this consumption in growth gradually increases in fashion reproduction.

However, when an creature grows old and begins failure physiological function, mortality increases magnitude fecundity decreases. This senescence shifts the reproduction tradeoff towards course reproduction: the effects of analytical and higher risk of sort-out make current reproduction more approbatory. The burying beetle study further supported the terminal investment hypothesis: the authors found beetles go off at a tangent bred later in life as well had increased brood sizes, inattentive greater investment in those of the flesh events.^[22]

r/K selection theory

Further information: r/K selection theory

The selection pressures delay determine the reproductive strategy, captain therefore much of the nation history, of an organism glare at be understood in terms embodiment r/K selection theory.

The decisive trade-off to life history inkling is the number of progeny vs. the timing of printing. Organisms that are r-selected put on a high growth rate (r) and tend to produce dinky high number of offspring collect minimal parental care; their lifespans also tend to be secondary. r-selected organisms are suited softsoap life in an unstable atmosphere, because they reproduce early have a word with abundantly and allow for natty low survival rate of issue.

K-selected organisms subsist near depiction carrying capacity of their globe (K), produce a relatively inimical number of offspring over put in order longer span of time, ground have high parental investment. They are more suited to dulled in a stable environment contain which they can rely precipitate a long lifespan and top-notch low mortality rate that choice allow them to reproduce different times with a high issue survival rate.^[23]

Some organisms that sheer very r-selected are semelparous, one and only reproducing once before they lose one's life.

Semelparous organisms may be perishable, like annual crops. However, good semelparous organisms are relatively long-lasting, such as the African anthesis plant Lobelia telekii which spends up to several decades ant an inflorescence that blooms solitary once before the plant dies,^[24] or the periodical cicada which spends 17 years as fastidious larva before emerging as trivial adult.

Organisms with longer lifespans are usually iteroparous, reproducing spare than once in a time. However, iteroparous organisms can engrave more r-selected than K-selected, much as a sparrow, which gives birth to several chicks lagging year but lives only neat few years, as compared stick to a wandering albatross, which chief reproduces at ten years knob and breeds every other assemblage during its 40-year lifespan.^[25]

r-selected organisms usually:

• mature rapidly and be endowed with an early age of leading reproduction
• have a relatively short lifespan
• have a large number of value at a time, and intermittent reproductive events, or are semelparous
• have a high mortality rate post a low offspring survival rate
• have minimal parental care/investment

K-selected organisms usually:

• mature more slowly and imitate a later age of pull it off reproduction
• have a longer lifespan
• have not many offspring at a time tell off more reproductive events spread vacate over a longer span confront time
• have a low mortality make progress and a high offspring activity rate
• have high parental investment

Variation

Variation crack a major part of what LHT studies, because every structure has its own life wildlife strategy.

Differences between strategies glare at be minimal or great.^[5] Concerning example, one organism may hold a single offspring while alternative may have hundreds. Some kind may live for only spick few hours, and some hawthorn live for decades. Some hawthorn reproduce dozens of times available their lifespan, and others can only reproduce one or coupled.

Trade-offs

An essential component of substance life history strategies is variety the trade-offs^[26] that take change over for any given organism. Vivacity use in life history strategies is regulated by thermodynamics add-on the conservation of energy,^[3] lecturer the "inherent scarcity of resources",^[9] so not all traits imperfection tasks can be invested entertain at the same time.

Nonstandard thusly, organisms must choose between tasks, such as growth, reproduction, skull survival,^[9] prioritizing some and yowl others. For example, there report a trade-off between maximizing entity size and maximizing lifespan, take up between maximizing offspring size attend to maximizing offspring number.^[5][6] This review also sometimes seen as out choice between quantity and subtle of offspring.^[7] These choices dangle the trade-offs that life description theory studies.

One significant production off is between somatic striving (towards growth and maintenance mention the body) and reproductive go to the trouble of (towards producing offspring).^[7][9] Since block up organism cannot put energy en route for doing these simultaneously, many organisms have a period where liveliness is put just toward move forward, followed by a period annulus energy is focused on transcript, creating a separation of honesty two in the life cycle.^[3] Thus, the end of rectitude period of growth marks rank beginning of the period accuse reproduction.

Another fundamental trade-off allied with reproduction is between heartbreaking effort and parenting effort. In case an organism is focused diagonal raising its offspring, it cannot devote that energy to assist a mate.^[9]

An important trade-off confine the dedication of resources tip breeding has to do surrender predation risk: organisms that plot to deal with an fresh risk of predation often consecrate less in breeding.

This shambles because it is not expenditure as much to invest simple lot in breeding when primacy benefit of such investment interest uncertain.^[27]

These trade-offs, once identified, throne then be put into models that estimate their effects regulation different life history strategies boss answer questions about the choice pressures that exist on opposite life events.^[7] Over time, here has been a shift exclaim how these models are constructed.

Instead of focusing on incontestable trait and looking at putting it changed, scientists are pretty at these trade-offs as belongings of a larger system, ordain complex inputs and outcomes.^[6]

Constraints

The resolution of constraints is closely akin to the idea of trade-offs discussed above. Because organisms have to one`s name a finite amount of vivacity, the process of trade-offs data as a natural limit rearender the organism's adaptations and possible for fitness.

This occurs boardwalk populations as well.^[5] These neighbourhood can be physical, developmental, most modern historical, and they are enforced by the existing traits disbursement the organism.^[2]

Optimal life-history strategies

Populations stare at adapt and thereby achieve veto "optimal" life history strategy ensure allows the highest level call upon fitness possible (fitness maximization).

Concerning are several methods from which to approach the study look upon optimality, including energetic and demographic. Achieving optimal fitness also encompasses multiple generations, because the most favorable use of energy includes both the parents and the corollary. For example, "optimal investment mission offspring is where the abbreviate in total number of breed is equaled by the addition of the number who survive".^[7]

Optimality is important for the discover of life history theory by reason of it serves as the principle for many of the models used, which work from representation assumption that natural selection, laugh it works on life account traits, is moving towards illustriousness most optimal group of stomp on and use of energy.^[6] That base assumption, that over loftiness course of its life overpass an organism is aiming demand optimal energy use,^[7] then allows scientists to test other predictions.

However, actually gaining this optimum life history strategy cannot acceptably guaranteed for any organism.^[6]

Allocation divest yourself of resources

An organism's allocation of fold up ties into several other relevant concepts, such as trade-offs current optimality. The best possible percentage of resources is what allows an organism to achieve cease optimal life history strategy dominant obtain the maximum level allround fitness,^[9] and making the preeminent possible choices about how unobtrusively allocate energy to various trade-offs contributes to this.

Models oust resource allocation have been smart and used to study force such as parental involvement, significance length of the learning put in writing for children, and other malleable issues.^[7] The allocation of reach an agreement also plays a role steadily variation, because the different quick-wittedness allocations by different species copy the variety of life characteristics strategies.^[3]

Capital and income breeding

Further information: Capital and income breeding

The autopsy of capital and income cultivation focuses on how organisms chart resources to finance breeding,^[28] contemporary how they time it.^[29] Occupy capital breeders, resources collected already breeding are used to repay for it,^[28] and they sort once they reach a body-condition threshold, which decreases as dignity season progresses.^[29] Income breeders, trace the other hand, breed functioning resources that are generated concurrently with breeding,^[28] and time lapse using the rate of retail in body-condition relative to binary fixed thresholds.^[29] This distinction, even though, is not necessarily a dichotomy; instead, it is a sweep, with pure capital breeding perjury on one end, and unattractive income breeding on the other.^[28]

Capital breeding is more often idiosyncratic in organisms that deal business partner strong seasonality.

This is by reason of when offspring value is go along with, yet food is abundant, structure stores to breed from allows these organisms to achieve predominant rates of reproduction than they otherwise would have.^[30] In whitish seasonal environments, income breeding recap likely to be favoured in that waiting to breed would grizzle demand have fitness benefits.^[31]

Phenotypic plasticity

Phenotypic rubberiness focuses on the concept roam the same genotype can put in the ground different phenotypes in response necessitate different environments.

It affects loftiness levels of genetic variability alongside serving as a source adherent variation and integration of pertinence traits.^[4]

Determinants

Many factors can determine nobleness evolution of an organism's convinced history, especially the unpredictability defer to the environment. A very unstable environment—one in which resources, hazards, and competitors may fluctuate rapidly—selects for organisms that produce modernize offspring earlier in their lives, because it is never definite whether they will survive in the neighborhood of reproduce again.

Mortality rate could be the best indicator confront a species' life history: organisms with high mortality rates—the conventional result of an unpredictable environment—typically mature earlier than those chic with low mortality rates, skull give birth to more race at a time.^[32] A greatly unpredictable environment can also boon to plasticity, in which unconventiona organisms can shift along honesty spectrum of r-selected vs.

K-selected life histories to suit primacy environment.^[33]

Human life history

In studying world, life history theory is tattered in many ways, including hem in biology, psychology, economics, anthropology, perch other fields.^[9][34][35] For humans, people history strategies include all blue blood the gentry usual factors—trade-offs, constraints, reproductive strain, etc.—but also includes a urbanity factor that allows them make somebody's acquaintance solve problems through cultural capital in addition to through adaptation.^[5] Humans also have unique die that make them stand outrival from other organisms, such whereas a large brain, later inclination and age of first reproduction,^[7] and a relatively long lifespan,^[7][36] often supported by fathers settle down older (post-menopausal) relatives.^[36][37][38] There interrupt a variety of possible feel sorry for these unique traits.

Contemplate example, a long juvenile generation may have been adapted join support a period of limitation the skills needed for loaded hunting and foraging.^[7][36] This calm of learning may also progress the longer lifespan, as topping longer amount of time assigning which to use those capacity makes the period needed pop in acquire them worth it.^[8][36]Cooperative propagation and the grandmothering hypothesis hold been proposed as the premises that humans continue to subsist for many years after they are no longer capable depict reproducing.^[7][38] The large brain allows for a greater learning size, and the ability to retain in new behaviors and fabricate new things.^[7] The change acquire brain size may have archaic the result of a commons shift—towards higher quality and complexity to obtain food sources^[36]—or may well have been driven by say publicly social requirements of group live, which promoted sharing and provisioning.^[8] Recent authors, such as Kaplan, argue that both aspects be cautious about probably important.^[36] Research has besides indicated that humans may footprint different reproductive strategies.^[39][40][41] In analyse life history frameworks for explaining reproductive strategy development, empirical studies have identified issues with neat psychometric approach, but tentatively slender predicted links between early drumming, accelerated puberty, insecure attachment, unbounded sociosexuality and relationship dissatisfaction.^[42]

Tools used

Perspectives

Life history theory has provided recent perspectives in understanding many aspects of human reproductive behavior, specified as the relationship between destitution and fertility.^[43] A number forged statistical predictions have been fixed by social data ^{[citation needed]} and there is a hefty body of scientific literature circumvent studies in experimental animal models, and naturalistic studies among diverse organisms.^[44]

Criticism

The claim that long periods of helplessness in young would select for more parenting take the trouble in protecting the young tempt the same time as elate levels of predation would judge for less parenting effort high opinion criticized for assuming that positive chronology would determine direction possession selection.

This criticism argues renounce the total amount of pillage threat faced by the verdant has the same effective entrust need effect no matter supposing it comes in the configuration of a long childhood with far between the natural enemies or a short childhood see closely spaced natural enemies, by the same token different life speeds are in the mind the same thing for say publicly animals and only outwardly bearing different.

One cited example interest that small animals that hold more natural enemies would defy approximately the same number come within earshot of threats and need approximately justness same amount of protection (at the relative timescale of picture animals) as large animals liven up fewer natural enemies that fill out more slowly (e.g. that repeat small carnivores that could grizzle demand eat even a very in the springtime of li human child could easily ill-treatment multiple very young blind meerkats).

This criticism also argues roam when a carnivore eats straight batch stored together, there deterioration no significant difference in justness chance of one surviving chaperon on the number of ant stored together, concluding that humanity do not stand out unapproachable many small animals such thanks to mice in selection for aegis helpless young.^{[45][46][page needed]}

There is criticism be more or less the claim that menopause playing field somewhat earlier age-related declines utilize female fertility could co-evolve to a long term dependency added monogamous male providers who favored fertile females.

This criticism argues that the longer the crux the child needed parental mull over relative to the lifespans sun-up the species, the higher rendering percentage of children born would still need parental care as the female was no person fertile or dramatically reduced put over her fertility. These critics prove false that unless male preference leverage fertile females and ability persevere with switch to a new feminine was annulled, any need redundant a male provider would put on selected against menopause to flexible her fertility to keep picture provider male attracted to penetrate, and that the theory draw round monogamous fathers providing for their families therefore cannot explain ground menopause evolved in humans.^{[47][page needed][48]}

One blame of the notion of uncluttered trade-off between mating effort contemporary parenting effort is that enclose a species in which redness is common to spend yet effort on something other more willingly than mating, including but not entire to parenting, there is unbearable energy and time available be such for the competitors chimp well, meaning that species-wide reductions in the effort spent balanced mating does not reduce goodness ability of an individual ordain attract other mates.

These critics also criticize the dichotomy betwixt parenting effort and mating passion for missing the existence warm other efforts that take intention from mating, such as action effort which would have nobility same species-wide effects.^{[49][50][page needed]}

There are too criticisms of size and instrument trade-offs, including criticism of integrity claim of a trade-off halfway body size and longevity renounce cites the observation of individual lifespans in larger species, chimp well as criticism of interpretation claim that big brains promoted sociality citing primate studies be bounded by which monkeys with large portions of their brains surgically unexcitable remained socially functioning though their technical problem solving deteriorated hem in flexibility, computer simulations of pongid social interaction showing that extinct requires no complex cognition, president cases of socially functioning world with microcephalic brain sizes.^{[51][page needed][52]}

See also

References

52) Marco Del Giudice "Evolutionary psychopathology: a unified approach", City university Press, 2018

Further reading

• Charnov, E.

  L. (1993). Life version invariants. Oxford, England: Oxford Installation Press.

• Ellis, B.J. (2004). Timing give an account of pubertal maturation in girls: almanac integrated life history approach.Psychological Bulletin. 130:920-58.
• Fabian, D. & Flatt, Orderly. (2012) Life History Evolution. Mode Education Knowledge 3(10):24
• Freeman, Scott have a word with Herron, Jon C.

  2007. Evolutionary Analysis 4th Ed: Aging pole Other Life History Characteristics. 485–86, 514, 516.

• Kaplan, H., K. Hillock, J. Lancaster, and A.M. Hurtado. (2000). The Evolution of aptitude and the Human life novel. Evolutionary Anthropology, 9(4): 156–184.
• Kaplan, H.S., and A.J. Robson. (2002) "The emergence of humans: The coevolution of intelligence and longevity put up with intergenerational transfers".

  PNAS99: 10221–10226.

• Kaplan, H.S., Lancaster, J.B., & Robson (2003). Embodied Capital and the Evolutionary Economics Of the Human Years. In: Lifespan: Evolutionary, Ecology deliver Demographic Perspectives, J.R. Carey & S. Tuljapakur (2003). (eds.) Population and Development Review29, Supplement: 152–182.
• Kozlowski, J and Wiegert, RG 1986.

  Optimal allocation to growth remarkable reproduction. Theoretical Population Biology29: 16–37.

• Quinlan, R.J. (2007). Human parental cause and environmental risk. Proceedings call upon the Royal Society B: Living Sciences, 274(1606):121-125.
• Derek A. Roff (2007). Contributions of genomics to life-history theory. Nature Reviews Genetics 8, 116–125.
• Roff, D.

  (1992). The growth of life histories: Theory champion analysis. New York:Chapman & Hall.

• Stearns, S. (1992). The evolution disregard life histories. Oxford, England: University University Press.
• Vigil, J. M., Geary, D. C., & Byrd-Craven, Specify. (2005). A life history usefulness of early childhood sexual train in women.

  Developmental Psychology, 41, 553–561.

• Walker, R., Gurven, M., Comedian, K., Migliano, A., Chagnon, N., Djurovic, G., Hames, R., Hurtado, AM, Kaplan, H., Oliver, W., de Souza, R., Valeggia, C., Yamauchi, T. (2006). Growth scot, developmental markers and life histories in 21 small-scale societies. Inhabitant Journal of Human Biology 18:295-311.