The Evolution Institute has partnered with Cambridge University Press to bring you an exciting new publication series: Cambridge Elements in Applied Evolutionary Science. The following text was written by Dr. Emily Emmott, a Human Behavioral Ecologist at University College London and author of the first Element of this series titled Improving Breastfeeding Rates: Evolutionary Anthropological Insights for Public Health. If you are interested in the publication, you can go here to the Cambridge University Press Website.
I came to the topic of breastfeeding almost accidentally during my PhD research, where I was researching the impact of allomothers (i.e., non-maternal caregivers) on maternal investments and child outcomes in the UK. Evolutionary anthropologists argue that humans evolved a system of cooperative childrearing, where multiple caregivers are required around the mother and child. As a PhD student, I wanted to find out if and how this cooperative childrearing system exists in a post-industrialised, low-fertility context.
Breastfeeding was a maternal investment behaviour I picked out by chance, mainly because there was data on breastfeeding initiation and duration in the UK cohort datasets I was using. Back then, I knew almost nothing about breastfeeding, although I’d seen some relatives breastfeed, and had heard of the phrase “breast is best” from a long-running public health campaign in England. As I began my research, I found out that breastfeeding is associated with numerous health and developmental benefits for the infant, most notably a reduction in the risk of infectious diseases, which is of course the biggest causes of infant hospitalisation and mortality. Despite these benefits, globally, only an estimated 43 per cent of infants met the WHO recommendation of being exclusively breastfed for six months in 2015. The statistics for the UK was even worse, with only 1 per cent of infants being exclusively breastfed for 6 month back in 2010 – one of the lowest in the world.
Many experts pointed to the “culture of formula feeding” in countries such as the UK, which normalises bottle feeding as the default mode of feeding. Women are more likely to see formula feeding on TV and in public, and some women may have never seen an infant or child being breastfed in real life. With breastfeeding being largely absent from society, the low rates of breastfeeding is self-perpetuated by the lack of knowledge around breastfeeding, as well as lack of societal-level support for breastfeeding – meaning women who want to breastfeed face many barriers. Therefore, for several decades, public health campaigns and interventions in the UK targeted this formula-feeding culture by actively promoting the benefits of breastfeeding and addressing the “breastfeeding knowledge-gap” among pregnant women and mothers.
However, as I outline in my new Element, Improving Breastfeeding Rates: An Evolutionary Anthropological Perspective, such public health policies and interventions have not been particularly effective at improving breastfeeding rates. From an evolutionary perspective, at first, this may seem puzzling: If breastfeeding is so good for the baby’s health and survival, why doesn’t everyone breastfeed and for longer?
As a human behavioural ecologist, I started by wondering whether “not breastfeeding” could be an optimal strategy for some women in post-industrialised contexts where formula milk is relatively accessible. Tully and Ball (2011) had outlined how breastfeeding decisions are influenced by mother-offspring conflict, where babies tend to want more than what is most optimal for maternal inclusive fitness. I hypothesised that, where allomothers were available to provide direct care to infants, then there may be a fitness incentive to reduce breastfeeding: first, because the opportunity costs of breastfeeding to the mother increases (because allomothers cannot care for your baby easily when mothers breastfeed on demand), and second, because the cost of not breastfeeding is greatly reduced for the offspring when they can have formula instead. This led to my first paper on the topic, which found that practical caregiving support from grandmothers and fathers was associated with lower breastfeeding initiation and duration in the UK. Over the next decade, I focused on understanding the complex pathways between different types of support from different sources and infant feeding, guided by evolutionary theory.
Overall, my research has led me to challenge the assumption that lack of knowledge and ignorance is the key driver of low breastfeeding rates in the UK. I would bet that most women know breastfeeding is “good” for their baby, which would explain why breastfeeding initiation rates in England, UK, increased from 66% in 2005/06 to 74% in 2010/11. However, by 6-8 weeks after birth, breastfeeding rates drop to around 45-48%. Many mothers report they would have liked to breastfeed for longer, and had to stop before they wanted to, and this is often accompanied by a sense of guilt and failure. But, from an evolutionary perspective, it is unrealistic to expect mothers to focus solely on maximising infant health. Life is messy, with competing demands; you may need to invest in other children, invest in resource acquisition/work, or invest in yourself. Breastfeeding is a complex, costly and skilled behaviour, and it requires time and dedication. Simply put, even if you have the desire to breastfeed, it doesn’t mean you can prioritise it and make it happen – you need extensive support from multiple people.
When I had my own baby in 2021, my breastfeeding experience was initially tough and relentless. In the haze of utter exhaustion and frustration during the first few months, messages such as “breastfeeding leads to higher IQ for baby” and “breastfeeding leads to better bonding” seemed irrelevant and pointless. When my nipples were bleeding because of my baby’s tongue tie, and he demanded to be cluster fed for 5-6 hours every evening for weeks, information on how to get a “good latch” was also pointless. I needed people around me to bring me water, to feed me, to reassure me, to share stories of their infant feeding experience, and to wipe away my tears. Breastfeeding did eventually get easier for me – so much so that we stopped giving any formula/pumped breastmilk as top-ups, as dealing with bottles became too inconvenient. Occasionally, breastfeeding was even entertaining, as I watched my crawling baby turn into a contortionist while he fed.
Western family and childrearing norms tend to centre on the nuclear family, with expectation that parents, usually mothers, have primary responsibility for raising their children. This is a relatively novel and unusual norm, conflicting with the evolved system of cooperative childrearing in humans. In fact, these norms do not reflect reality. As humans, it takes a village to breastfeed, even in post-industrialised, low-fertility contexts. To improve breastfeeding rates in places like the UK, we should stop expecting mothers to be self-sacrificial, assuming they would opt to invest everything into breastfeeding once they know how “good” it is for the baby (which also implicitly and erroneously frames formula-feeding mothers/parents as not investing in their babies). Instead, we need to lower the costs of breastfeeding, for example thorough appropriate levels of paid maternity leave (so mothers do not have to juggle breastfeeding and paid work) and provision of affordable childcare (so mothers do not have to juggle breastfeeding and looking after older children). We also need to ensure families and communities understanding how much support mothers need, in general. Only then will mothers be free to concentrate on breastfeeding – if that’s what they decide is right for them.