The Natural Age of Weaning

August 23, 2017 at 8:25 pm

Mothers today are bombarded with all kinds of conflicting advice on how long they should breastfeed. Some are told it’s “gross” or “weird” to nurse beyond six or 12 months. Some consider nursing a 2 or 3-year-old to be “extended” breastfeeding.

The World Heath Organization recommendation is “up to two years or beyond,” which is confusing in and of itself. “Up to” sounds like a maximum, with a “beyond” thrown on the end to satisfy La Leche League members who likely complained.

When I wrote a post titled “Why I Still Breastfeed My 5-Year-Old” – who is still nursing at 6, by the way – I got all kinds of emotional reactions.

The thing is these numbers and reactions are based solely on our cultural norms, not on our biological needs. Hardly anyone is asking the question “what is the natural age of weaning, according to science?”

In a meta-analysis of methodologies for determining the natural age of weaning in primates and other large mammals, Anthropologist Katherine Dettwyler attempts to estimate that age in humans.

According to five of the six methods, the natural age of weaning in humans is between 4.5 and 7 years old:

1. In a study of 21 species of non-human primates (monkeys and apes), the offspring were weaned at the same time they were getting their first permanent molars. In humans, that would be 5.5-6.0 years.

2. Chimpanzees and gorillas nurse their offspring six times the length of gestation. In humans, that would be 4.5 years of nursing.

3. One study of primates showed that the offspring were weaned when they had reached about 1/3 their adult weight. This happens in humans at about 5-7 years.

4. A comparison of weaning age and sexual maturity in non-human primates suggests a weaning age about half-way to reproductive maturity, 6 or 7 years for humans.

5. Large mammals nurse their offspring until they have quadrupled their birth weight. In humans, quadrupling of birth weight usually occurs between 2.5 and 3.5 years.

6. Studies have shown that a child’s immune system doesn’t completely mature until about 6 years of age. It is well established that breast milk helps develop the immune system and augment it with maternal antibodies as long as breast milk is produced.

Note that the only study that suggested a natural weaning age of less than 4.5 years was a study of all large mammals, not primates specifically. Considering the well-documented link between longer-term breastfeeding and higher IQ, it seems to make sense that primates, especially humans, would breastfeed longer than other mammals.

Dettwyler and others note that in cultures where children are allowed to nurse “as long as they want,” they very rarely wean themselves before age 4, without “arguments or emotional trauma.”

“Most of my experience is with children who weaned between three and four, but clinical observations and research suggest that a completely child-led weaning is unlikely to take place before the child turns four,” writes La Leche League educator Norma Jean Bumgarner¬† in her book Mothering Your Nursing Toddler.

Of course many children spontaneously stop nursing long before age 4, but Bumgarner says there are usually conditions outside the child’s control that contribute to their “decision,” such as parents pushing solid foods and other liquids as young as 6 months — sometimes even requiring babies and toddlers to fill up on something else before the breast is offered. (I briefly babysat a 7-month-old whose father literally force-fed her large portions of “baby food” before each feeding to relieve his breastfeeding wife.)

Some babies seem less interested in nursing between nine and 14 months old, as they become more mobile and distracted by other things, Bumgarner says.

“If you don’t want to nurse a toddler, this may be the least traumatic weaning time there will be for at least two or three more years,” she writes.

If you’re goal is natural weaning, “this may be a sort of danger time in which you may want to make sure your nursing relationship is not interrupted or disturbed.”

Often times children who appeared to “self-wean” as babies or toddlers try to resume nursing at 3 or 4 or even 5 years old, especially if they have a younger sibling nursing. Bumgarner says not to worry.

“He is not returning to babyhood, but picking up a behavior that is appropriate for his age.”

In the months that follow an apparent decision to wean, many children encounter rough spots that cause them to reconsider, Bumgarner says.

“A request to nurse from a child who has not nursed for a while is usually a request for reassurance and acceptance. It is much easier for a little person to wean himself if he knows his decision does not have to be final.”

Children usually wean at a time when their lives are otherwise easy and stable, she says.

“When she asks to nurse again after such a long time you can be sure that she has just come to a time in her life which she can handle better if she can still nurse a bit. Once she works her way past it, she will get back to the business of weaning.”

You can find more excerpts from Bumgarner’s book on The Natural Child Project’s website.

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