prepares for her work as a toddler nurses. (Japan, ) In some cultures, weaning progresses with the introduction of feeding the child food that has been prechewed by the parent along with continued breastfeeding, a practice known as
premastication. The practice was important throughout human history in that it naturally gave a child a greatly improved protein source in addition to preventing iron deficiency. However, premasticated food from caregivers of lower socioeconomic status in areas of endemic diseases can result in the passing of the disease to the child. How and when to wean a human infant is controversial. The American Academy of Pediatrics recommends feeding a baby only breast milk for the first six months of its life. Many mothers find breastfeeding challenging, especially in countries where many mothers have to return to work relatively soon after the birth of their child. The American Academy of Pediatrics, the World Health Organization, the National Health Service Choices UK, and the National Health & Medical Research Council in Australia recommend waiting until six months to introduce baby food. However, many baby food companies market their "stage 1" foods to children between four and six months old with the precaution that the food is meant to be consumed in addition to breast milk or formula and is just for "practice". These practice foods are generally soft and runny. Examples include mashed fruit and vegetables. Certain foods are recommended to be avoided. The United Kingdom's NHS recommends withholding foods including those "that contain wheat, gluten, nuts, peanuts, peanut products, seeds, liver, eggs, fish, shellfish, cows' milk and soft or unpasteurised cheese" until a baby is six months old, as they may cause food allergies or make the baby ill. However, recommendations such as these have been called into question by research that suggests early exposure to potential allergens does not increase the likelihood of allergies, and in some cases reduces it. Evidence from clinical trials shows that nutrition education of family members about infant weaning practices probably has a positive effect on babies' weight and height at 12 months compared with conventional management of weaning. No matter what age baby food is introduced, it is generally a very messy affair, as young children do not have the coordination to eat neatly. Coordination for using utensils properly and eating with dexterity takes years to develop. Many babies begin using utensils between 10 and 14 months, but most will not be able to feed themselves sufficiently well until about two or three years of age.
Weaning conflict At this point, the mother tries to force the infant to cease nursing, while the infant attempts to force the mother to continue. From an evolutionary perspective, weaning conflict may be considered the result of the cost of continued nursing to the mother, perhaps in terms of reduced ability to raise future offspring, exceeding the benefits to the mother in terms of increased survival of the current infant. This can come about because future offspring will be equally related to the mother as the current infant, but will share less than 100% of the current infant's
genes. So, from the perspective of the mother's evolutionary fitness, it makes sense for her to cease nursing the current infant as soon as the cost to future offspring exceeds the benefit to the current infant. Weaning conflict has been studied for a variety of mammal species, including
primates and
canines.
Age There are significant individual and cultural variations in regards to weaning. Scientifically, one can ask various questions; some of the most straightforwardly empirical include: • At what age do children self-wean? • At what age do various societies normatively choose to wean? • In comparison with other animals, especially similar primates, by various measures. As there are significant ranges and skew in these numbers (some infants are never nursed, or only nursed briefly, for instance), looking at the
median (half-way mark) is more useful than looking at the
average. This depends on the measure, for example: weaning in non-human primates is often associated with eruption of
permanent molars (humans: to 6 years); comparing duration of nursing to length of pregnancy (gestation time) yields a factor of about 6 in chimpanzees and gorillas (humans: months = 54 months = years); body weight may be compared to birth weight (quadrupling of birth weight yields about to years for humans; of adult weight yields 5 to 7 years for humans); and similarly for other measures. Other studies are possible, as in psychological factors. For example,
Barbara Rogoff has noted, citing a 1953 study by Whiting & Child, that the most distressing time to wean a child is at 13–18 months. After this peak, weaning becomes progressively easier and less distressing for the child, with "older children frequently wean[ing] themselves". In her study of pre-war
Japanese society The Chrysanthemum and the Sword,
Ruth Benedict documents that Japanese children were usually not weaned until soon before a new sibling arrives. However the government promoted eighth-month weaning which was reluctantly adopted by the middle-class in the benefit of the baby. The factor that the
Japanese meals did not include cow's milk or special vegetables for children also favored late weaning. ==In other mammals==