It is a truism common to nearly all family gatherings that grandparents will frequently remark on how fast their beloved grandchildren seem to be growing up these days.
But now, instead of provoking a bout of eye-rolling at such platitudes, a new report seems to show the old folk were right all along: boys are indeed hitting puberty earlier than they used to.
The study by the American Academy of Paediatrics, first revealed by the New York Times, was published at the weekend. Widely seen as the best measure of the onset of puberty in American boys, it demonstrated they are showing signs of puberty six months to two years earlier than previously assumed.
The surprise finding builds on previous discoveries that appeared to show girls have also been developing faster.
A study in 2010, which was published in the US Journal of Pediatrics, created headlines when it revealed girls were hitting puberty earlier, with some developing breasts as young as seven.
Other studies have revealed the same trend in girls all over the world.
Now the academy's study, officially unveiled at a national conference in the US, is showing the same trends in boys.
It primarily identified the signs of puberty as the growth in size of testicles and largely shied away from speculating on what may be causing the shift, though it did refer to changes in diet, the fact that modern children are being less physically active and other environmental shifts.
All that has led some to speculate that weight gain might be a possible factor.
It certainly might explain the earlier development among girls, as body fat is linked to production of the female hormone oestrogen. But the link might be less clear with boys.
Also, it is not certain if weight gain is a trigger for puberty or simply a consequence of it.
The investigation also showed that American boys are divided by race when it comes to puberty.
The study found that, on average, black American boys started showing signs of puberty a little older than the age of 9, while their white and Hispanic counterparts did likewise just after turning 10.
Prior to this study, 11 was generally seen as the age of hitting puberty for boys.
The study looked at more than 4000 boys in 41 US states in an age range of 6 to 16 years.