It is one of the oldest jobs in the world, and it makes a vital contribution to the modern economy - but we know very little about it, and rarely celebrate it publicly. It is that exquisite art: grandparenting.
As a new study by Professors Doreen Rosenthal and Susan Moore notes, grandmothers provide an average of 12 hours' childcare every week. Their book, New Age Nannas: Being a Grandmother in the 21st Century, reports a survey of 1200 grandmothers, aged from their 30s to early 90s.
They found that grandmothers are increasingly fit and healthy, playing important roles in their children's and grandchildren's lives. Some are still working, others are retired, but they maintain an engagement with family and the broader world, which was seemingly foreign to some previous generations.
This increased wellbeing is partly because of lifestyles, including better nutrition and increased exercise, and broader social trends like modern medicine and universal health care.
But it is also, I suspect, because of the childcare itself: the intimacy and physicality of caring for children keep us stimulated, in an active congress with the world. It can also be a salve for loneliness among those widowed or separated.
Children benefit from this arrangement, too, with grandmothers providing new kinds of play, and a living connection to the remembered past. When I was a child, my own grandmother used to tell stories of her childhood and youth in the 1920s and '30s - the Jazz Age, in which, as a pianist and band leader, she played a lively role.
The study also notes that grandmothers can be ''confidantes and wisdom-givers'' - close enough to observe and sympathise, but distanced enough to provide welcome counsel.
There are also the ever-present treats: chocolate sandwiches, Dora dolls, apocalyptic mud play. These can frustrate parents, but are often more harmless than they seem. They give welcome but hopefully brief respite from parental austerity - the momentary transgressions that help maintain the taboos.
In other words, the involvement of nannas and grandmas is, at its best, reciprocally vital: healthy for parents, children and grandparents alike. Rosenthal and Moore have not yet published research on grandfathers, who have traditionally played less of an immediate role in care-giving. But with the right attitude and opportunities, they are equally capable of contributing to familial wellbeing.
Perhaps the most unnoticed benefit of this generational intermingling is its existential revelation: it shows grandparents as whole human beings, not quiet exiles from the adult world.
In all families, there is the danger that people become symbols: cooking and cleaning mother, the providing father, the quaint, archaic nanna. ''I loved my grandparents, but they seemed very old - certainly for as long as I remember them, they were stereotypically old,'' Professor Rosenthal told Melbourne University's Voice lift-out.
''Neither they nor their friends drove. The women didn't work outside the home.'' There is nothing inherently wrong with this, of course. But it can lead to an unnecessary distance between generations. The psyche's subtle inner universe can become a more limited persona or role.
But as grandmothers spend more hours with their grandchildren, many kids will be given an important opportunity: to see their nannas and grandmas in all their subtlety and vivacity; with their variable moods, ideas, memories. They may not notice this at first, but over the decades, this will provide a valuable corrective to the myth that older generations are just faded sepia versions of real human beings.
And this is not only valuable for children. Parents get to rediscover their own mothers and fathers as caregivers, and reflect on their impressions of childhood. This enriches memory, and offers clarifying contrasts with familiar habits. And the grandmothers, meanwhile, can redefine themselves as child-rearers: a new, mindful balance of proximity and detachment. Often more educated and professional than their predecessors, the ''new-age nannas'' can combine public achievement with domestic finesse, and hopefully the ripe wisdom of age.
Sadly, because of events like death, distance and divorce, not all families can experience these transformations. But it is worth recognising and celebrating nonetheless: the ancient, and very modern, grandparental vocation.
Dr Damon Young is a philosopher, and the author of Distraction: A Philosopher's Guide to Being Free.