Association of negative affect with correlates of net fitness costs--论文代写范文精选

任何生物都可以被视为一个功能组件,每个设计的自然选择在环境中解决一个特定的问题。大脑和身体的其他部位一样,进化心理学是进化生物学的一个分支,试图确定大脑的功能组件。下面的report代写范文进行详述。

Abstract 
This section will specify in greater detail some of the adaptive problems faced by ancestral human mothers, and will propose one deceptively simple but very important psychological function that would have been necessary to address these problems, namely, that ancestral mothers needed to know when their costs were exceeding their benefits. PPD may, in part, assist the mother in determining whether she is suffering (or has suffered) circumstances that were associated with net fitness costs over evolutionary time. The other two components of the defection hypothesis, that PPD may function to reduce investment by the mother or increase the investment of others, will be discussed in later sections.

The functional properties of organisms are called adaptations, and the terms function and adaptation will be used interchangeably in this paper. Briefly, adaptations evolved because they solved the recurring problems of survival and reproduction discussed in the previous section. Hearts, lungs, and eyes are typical examples of adaptations, and each evolved to solve an important problem: hearts circulate nutrients to other tissues in the body, lungs extract oxygen from the atmosphere, and eyes collect visual information from the environment. These organs are recognized as adaptations because the features of each correspond closely to the problems they were intended to solve. This correspondence is called evidence of design. The chambers and dense muscles of the heart are ideally designed for pumping blood, but poorly designed for absorbing large quantities of gaseous oxygen. 

The numerous cavities of delicate tissue that comprise the lungs are ideally designed for absorbing oxygen, but completely ineffectual for focusing light. In order to solve the many problems involved in reproduction, many adaptations are needed. Any organism can be therefore be viewed as a large but finite set of functional components, or adaptations, each of which designed by natural selection to solve a particular reproductive problem in ancestral environments. The brain, like the rest of the body, consists of a number of adaptations, with vision, hearing, smell, motor control, and physical pain being obvious examples. Evolutionary psychology is the subfield of evolutionary biology that is attempting to identify the functional components of the brain, often referred to as psychological adaptations (Barkow, Cosmides & Tooby, 1992; Daly & Wilson, 1983; Daly & Wilson, 1984; Symons, 1979). Like other adaptations, a psychological adaptation can be recognized by evidence of its having been designed by natural selection to solve a particular reproductive problem. For example, physical pain functions to inform an animal that its tissue is being damaged, provides information on the precise location of the damage, motivates the animal to withdraw from the damage-causing circumstances, and conditions the animal to avoid similar circumstances in the future. Each of these capabilities requires a sophisticated organization of the nervous system, and each would have facilitated reproduction of the organism. 

In general, psychological adaptations evolved to extract information from the environment that was relevant to reproductive problems, and to then generate behaviors, that, on average, 8 solved these problems. It will be argued here that PPD shows evidence of having been designed by natural selection to solve three important problems of the puerperium, and is therefore not an illness, but an adaptation. The suggestion that PPD is a functional component of human reproductive decision-making was first made by Daly and Wilson (1988), and Wilson and Daly (1994), who have published extensively on parental cognition in evolutionary perspective (Daly, 1987; Daly, 1995; Daly, 1980). In particular, Wilson and Daly (1994) pointed out that both lack of social support and infant problems were associated with PPD, and that, in accord with evolutionary expectations, PPD disinclined mothers to invest in their offspring. This functional hypothesis for PPD has been further elaborated by Hagen (1998; 1998; 1996; 1998), and Thornhill and Furlow (1998), and will be explored in detail here. Before proceeding, it is important to point out that adaptations can operate even though individuals may have no conscious awareness of their function. 

None of our ancestors had any awareness or understanding of the function of fever, for example. In an attempt to avoid lengthy and awkward sentences, however, I use the words “decide” and “should” to indicate the operation of an adaptation, with no conscious or moral intent implied. For example, the phrase “mothers decide to defect from their infants when...” is shorthand for “a maternal psychological adaptation to defect from the infant is activated when....” Similarly, the phrase “mothers should defect from their infants when...” is intended to be shorthand for “mothers who defected from their infants when..., would have had, on average, a greater number of descendants than those who did not defect.”

Costs of the puerperium 
The major benefit of bearing an offspring—a reproductively successful child—involves a substantial investment from the mother. The time, energy, and resources required to successfully rear human infants are enormous, a consequence of the considerable degree of brain growth and development that occurs postpartum (Lancaster, 1986). Human offspring are unable to fend for themselves, requiring mothers to provide several years of direct care. In addition to direct care, mothers in preindustrial populations provide all the fuel for brain development. Breast feeding is metabolically expensive, and the energetic costs of lactation are actually greater than the energetic costs of pregnancy (Worthington-Roberts, Vermeersch & Williams, 1985). The 36,000 kcal of fat that a female may have stored under ideal conditions is sufficient to provide only about one-third of the energy required to support four to five months of lactation (Widdowson, 1976). 

The typical woman in a preindustrial setting is unlikely to conform to this western ideal, however. She often begins pregnancy with lower nutritional reserves, gains little if any fat during pregnancy, may lactate for more than three years, may be 9 subject to special dietary restrictions during lactation, and must provide virtually all of the infant’s nutrition for at least the first six months postpartum (Wood, 1994). Lactation will occur at the expense of maternal stores, and the net effect of these differences is that the nutritional status of women in traditional societies often declines sharply over the course of lactation, a phenomenon referred to as maternal depletion syndrome (Bongaarts & Delgado, 1979; Miller & Huss-Ashmore, 1989). 

Nursing an infant can seriously impact the mother’s health. The postpartum period is clearly a very expensive one for the nursing mother, much more so than pregnancy. The decision to invest in the infant is consequently of critical importance, and a necessary functional component of the mother’s decision-making process is information on whether her costs are in fact exceeding her benefits. 

Many researchers have attempted to identify functions for psychological distress, neuroses, and depression which would compensate for their obvious costs (Alexander, 1986; Birtchnell, 1993; Gardner, 1982; Gilbert, 1989; Henderson, 1974; Henderson, 1981; McGuire & Troisi, 1998; Nesse, 1991; Nesse & Williams, 1995; Price, Sloman, Gardner, Gilbert & Rohde, 1994; Slavin & Kriegman, 1992; Thornhill & Thornhill, 1990; Thornhill & Thornhill, 1989; Watson & Andrews, unpublished ms; Wenegrat, 1995). Virtually all propose functions involving an adaptive response to varied interpersonal problems. 

In particular, several of these researchers have proposed that whereas physical pain functions to inform individuals that they have suffered a bodily injury, psychological pain informs individuals that they have suffered a nonbodily injury (sometimes referred to as a “social injury”) motivating them to cease activities which would further this injury, as well as to avoid any future situations which would also result in injury (Alexander, 1986; Nesse, 1991; Nesse & Williams, 1995; Thornhill & Thornhill, 1990; Thornhill & Thornhill, 1989; Tooby & Cosmides, 1990). A non-bodily injury is any circumstance, usually involving relationships with others, that was reliably associated with a reduction in reproductive fitness over evolutionary time, e.g., the death of children and relatives, loss of status, etc. An important symptom of PPD is a sad or depressed mood (APA, 1994). The first and most strongly supported functional hypothesis for PPD offered here is that sad or depressed mood is in fact information to the mother that she is suffering (or has recently suffered) circumstances that were reliably associated with net reproductive fitness costs over evolutionary time.

Failure to offset puerperal costs: hypothesized etiological factors for PPD 
If PPD functions, in part, to inform mothers that they are suffering or have suffered circumstances that were reliably associated with net reproductive fitness costs, then these circumstances should be important etiological factors for PPD. New mothers have just invested nine months in the new offspring, and they need to evaluate their decision to get pregnant, decisions made during pregnancy, and whether to continue to invest in the offspring in light of the following circumstances that would have either substantially increased their costs or reduced their benefits.

During our evolutionary history, investment by others was key to reducing the costs of child-rearing and increasing infant viability. Lack of social support, even in populations with access to modern health care, correlated in one study with lower birth weight babies, lower scores on the 5 minute Apgar test (which rates respiratory effect, muscle tone, heart rate, reflex irritability, and skin color 5 minutes after delivery) and labor difficulties (Collins et al., 1993). Numerous developmental problems can also significantly reduce infant viability. Poor neonatal functioning should be associated with negative affect. In addition to obvious infant problems, reliable predictors of infant problems, particularly those predictors that occur prepartum, would be very useful to ancestral mothers attempting to evaluate offspring viability. Pregnancy and delivery problems like gestational diabetes, pregnancy induced hypertension, and abnormal presentation are significant predictors of high child malformation and mortality rates even when mothers have access to modern medical care (see table 3; also see footnote 3 for possible confounding factors).  

51Due网站原创范文除特殊说明外一切图文著作权归51Due所有；未经51Due官方授权谢绝任何用途转载或刊发于媒体。如发生侵犯著作权现象，51Due保留一切法律追诉权。
更多report代写范文欢迎访问我们主页 www.51due.com 当然有report代写需求可以和我们24小时在线客服 QQ:800020041 联系交流。-X