For years, the backbone of Labour’s family policy has been to support mothers in their role as parents and to support them into work, in order to lift families out of poverty: a mix of parenting support programmes for mums and childcare. These are vital and always will be, but we have reached the limit of this approach. It is expensive and the money has run out. Jon Cruddas and Labour's Policy Review are looking at expanding this approach by looking for other resources in children’s lives – the social capital that is potentially available to children, such as fathers, grandparents, extended family and community.

Much research has been undertaken that shows the well-being and resilience of children is strongly linked to their stock of social capital: well connected children do better. They are surrounded by constantly available support in order to deal with both immediate difficulties and as they step into the worlds of work and of parenting.

On 6 March, Labour’s Policy Review organised a symposium on family policy and assembled a number of radical thinkers to come up with ideas about this "whole family" approach to policy making. Shadow ministers Lucy Powell, Lisa Nandy and Liz Kendall were involved and David Lammy and Harriet Harman also spoke.

If social capital, rather than just money, is going to be a resource we depend on, then that requires a pretty major development in our perspective. First, we must see families as more than only mothers caring for babies and children. And second, we have to look at how all those who also have parental roles – including fathers, grandmothers and grandfathers - support each other in families.

The singular maternal approach to parenting that is considered the norm has been shown to be a short-term historical blip dating back to the Industrial Revolution. Human parenting has been characterised for the vast majority of human history as a highly collective activity, where mothers have shared the care of infants, from day one, with a wider family group, often, but not always, including men. All members of the human family have evolved to fit this pattern of care. Mothers depend on substantial support, particularly in the first years of a child’s life. Fathers undergo hormonal changes when close to pregnant mothers and babies and these trigger patterns of caring behavior and a desire to stay closer to the children. And most importantly, babies have evolved to need and thrive on multiple attachments within a family group, the foundation for their future existence in a social world. Babies are remarkably good at reading individuals in their families and the relationships between them.

Support programmes for families have consistently been shown to be more effective when they engage with not just one carer, but with the caring group. The world’s leading researchers in this field, Phil & Carolyn Cowan, are currently working with Family Action and the Tavistock Centre for Couple Relationships to demonstrate that support for families specifically focusing on the quality of the couple relationship gets better outcomes. That’s because it works along the grain of how our parenting has evolved.

The way we parent changes depending on our environment and has always done. With the education of women making women vital to our economy, with the lack of war that takes men out of households, with the internet again breaking down the division between work and home, with fathers routinely attending the birth of babies and undergoing a much stronger bonding experience, we are entering a new era of family life. Families are changing and policy must do its best to catch up.

Over the last 30 years, the focus of building social capital has been the creation of networks of mothers that operate outside families. This has been right and will continue so long as mothers are deprived of the considerable support they need within the family during the early years. But as Jon Cruddas has made clear, we must widen this approach and actively encourage fathers (and grandfathers) and ensure that they too have the social support to engage directly in the care of children. As David Lammy has pointed out, we need much higher expectations of men when it comes to looking after children. We need to start thinking "Mums and Dads" instead of just "Mumsnet" or "Netmums".

We need to start at the beginning, in maternity care. I presented a project in Liverpool Women’s Hospital, Maternity Assist, where a digital extension of local maternity care is being developed that defaults to engaging with fathers and other family members – mothers can nominate as many key supporters as they wish to receive information and advice from the maternity service. Parenting support programmes should engage with the parenting group, not just a "primary carer" because that gets a better result.

At the heart of the matter is child development, which is the foundation of Labour’s Policy Review on families. We know that attachment between child and adults is the key to child wellbeing, influencing how the brain develops. We have to learn how multiple attachments work for babies and how a child’s relationship with different people in the family depends substantially on how the group operates and on the health of other relationships within the group. The idea of a "primary attachment" that needs supporting, and then "secondary" and other "lesser" attachments being left to look after themselves, is a profound misunderstanding of how things work in a collective environment. The relationships (in the plural) that a baby and child forms with close carers form the essence of their humanity. We need to support and build these. And not just because we have run out of money, which happens to be the case, but because that is the best thing we can do for our children in the 21st century.

Duncan Fisher is the co-founder of the Fatherhood Institute