The gentle hum of activity in The Herald newsroom was shattered abruptly on Monday as the doors imploded. Through them roared what at first glance appeared to be a chariot with two small boys between the shafts. At the helm, though not what you would describe as in charge, was Michael Tumelty, the paper's veteran music critic.

With his other half away on a rare break, 61-year-old Michael had been left to cope with their three-year-old twins and, equipped with two pairs of reins, he had bravely decided to make a foray into the city. Judging from the brow-mopping going on once this cheery duo had been brought to a halt, it's a good job Michael can take refuge in various concert halls on a regular basis. Yet as one of Britain's growing band of second-time-around fathers, he clearly derives huge pleasure from his hands-on role. "I have terrible arthritis but they keep me going. Once I'm running round the park with them, I don't have time to think about it. They often exhaust me but they're also good for me."

The deal is clearly mutual. Adam and Andrew are delightful lads, brimming with intelligence, confidence and fun. Recently one of them was listening to a recording of Für Elise, and inquired if it was Mozart. On being told it was Beethoven, this three-year-old's instant rejoinder was: "Sounds like Mozart." By an odd coincidence, music and food critic Conrad Wilson also boasts a second brood and once regaled Herald readers with a description of his daughter's first birthday party, at which she wolfed down courgette soup, seafood and polenta cake.

Meeting such children, you get the distinct impression that one day they will take the world by storm. Their worldly-wise parents are a bonus.

Messrs Tumelty and Wilson belong to a distinguished group. The veteran broadcaster Russell Davies has three-year-old twins. Radio 4 Today programme's anchorman, John Humphrys, author Garrison Keillor, and actors David Jason and Michael Douglas are all older dads. This week it emerged that, following Wendy Alexander's appointment as Labour parliamentary group leader at Holyrood, her husband, Professor Brian Ashcroft, is stepping down as director of the Fraser of Allander Institute to care for the couple's 18-month old twins, Caitlin and Michael.

As he joked to journalists, at 60 and with a 24-year-old daughter from his first marriage, he feels less like a "new man" than an old one. For obvious reasons, second-time fathers are often older than their partners and are likely to be at a better stage in their careers to scale down their work commitment.

There is certainly a social revolution in fatherhood taking place, with 68% of us now regarding the traditional model of male breadwinner and female homemaker as outdated. And though most of them work, today's fathers spend an average of two hours a day on child-related activity, an eight-fold rise since the mid-1970s. Most telling of all, nearly 80% of working dads with young children say they would be happy to stay at home while their wives go out to work. Were it not for the scandalous gender wage gap, more couples would try it. There is also an argument for replacing (better) maternity and (still paltry) paternity rights with gender-neutral parental leave. Even the proposal to introduce a right for fathers to take up to 26 weeks of their partners' unused maternity leave from 2009 doesn't achieve that. Yet in countries such as Norway and Sweden, it is starting to make a real difference. An added advantage is that it should eventually rid the system of a disinclination to employ women of child-bearing age and aspirations.

There are around 200,000 "housedads" in Britain, according to the latest census. It's not known how many of them are older men. While the changing role of fathers seems to be a cause of general rejoicing, the issue of older parents is much more fraught. It's in the news again this week because new, more reliable egg-freezing techniques have opened the possibility of women one day having more choice in when they have children. Once again we're hearing the old argument about the "biologically optimal" child-bearing window of 20 to 35, that women who postpone childbearing to get on with their careers risk "missing the boat" and relying on any technological fix is unwise. Yesterday it was reported that more than one-quarter of Scottish couples in their late 30s have difficulty conceiving.

This is certainly a serious issue. Fertility in Scotland is down from an average 3.1 births per woman to 1.5. As it happens, it was work carried out under Prof Ashcroft at Fraser of Allander that showed that more than 40% of female graduates are still childless in their late 40s. The flip side is worryingly high rates of teenage pregnancy and early motherhood among the most disadvantaged. The demographic implications of these statistics should worry us. How can we create a smart, successful Scotland if the brightest aren't reproducing and the poorest and least educated are passing on their disadvantage to the next generation? The answers have to be substantial state support to break the cycle of poverty and more thinking about how to make Scotland an attractive place for families.

But it is wrong to harangue educated women for putting their careers before motherhood. I can't speak for Wendy Alexander, but many modern women don't establish stable relationships until their mid-30s, never mind financial independence. In the most recent survey of childless women, more than one-third cited failure to find a partner as the main reason.

As a second wife, who embarked on motherhood at 35 and finished at 42, I have to say that for me there wasn't a choice. My husband is four years older. At times it has been challenging, to say the least, not only because one has less energy at 3am but mainly because our babies arrived at the same time as our parents were slowly taking their leave, a common problem for we alma maters. It was summed up by an enervating expedition to a farm life centre: a restless babe in arms, two hyperactive horse-mad little girls, Grandpa (three strokes) in his wheelchair and Granny (Alzheimer's) wandering off every few minutes to talk to goats. After days like that, coming to work felt like a welcome break. Of course, the other issue is that we may not be around to meet our grandchildren. If my son has children at the same age I had him, I will be 85 and probably not much use for helping out with childcare. In fact, he is likely to face the same double whammy that we did.

Couples who embark on parenthood late need to know the downside. Apart from infertility problems, there are more risks of complications in pregnancy and of birth defects. On the plus side, children of older parents tend to be better off and better educated. We may not be wiser but at least I felt we had established values. Perhaps we were less selfish because we had already achieved a lot of our ambitions. I'm pretty sure I made a better mum at 40 than I would have been at 20. No reason, then, to apologise for our late arrivals.