It's not unusual to hear racing commentators talk about a horse developing from year to year, and that's especially true of younger animals. In flat racing that development is most important as juveniles mature into adult horses.
But what does that actually mean? How quickly do horses mature and how should we see that in comparison with humans? In their early years there is no flat rate comparison between the two. That only clicks into place once horses reach the age of five, when each additional year is roughly the equivalent of 2 1/2 human years.
For the first four years of a horse’s life it's a completely different story. To begin with, a newborn foal has the capacity of a two-year-old child. The most obvious comparison is that foal can walk immediately it is born. During its first year of life a horse will age all of six human years, so that by the time that first 12 months have elapsed it is effectively eight years old.
That rate of growth slows in each of the subsequent three years, but when it's two years old (real-time) a horse has grown another five human years and is entering its teenage years. The troublesome teens span a horse’s third and fourth years, and by the time these are over we have a mature human equivalent of 20 years on the clock.
Then things settle down, and from the age of five onwards each horse year represents 2 1/2 human years.
Does any of this matter when we're betting? Well, I think it does, particularly in flat racing. Remembering that every horse has its official birthday on 1 January, let's compare the maturity of an animal foaled in early February with one born in late April, the difference of just 12 weeks. The key point is that a horse matures by five human years in its second year.
The early foal will have its official second birthday and become eligible to race when it's virtually 22 months old, or 12 in human terms. The later foal, just 13 weeks younger in real time is effectively a full year and a half younger, still a 10 and a half year old child. When the flat season starts at the end of March, it’s likely putting a 14yo child against a 12yo.
That "18 month gap" is a huge difference to carry through a first season of racing. It would be in any sporting contest, which is why junior Rugby football are organised in annual year groups, under 9s, under 10s, under 11s and so on.
Think about those late season big two-year-old races like Doncaster's Racing Post Trophy or Newmarket's Dewhurst, both run during October. Whilst the younger colt is barely a human 15 year old, the earlier one is already a strapping 16-year-old.
Those “18 months” are just as relevant during a horse’s three-year-old career. Let's look at those relative ages when the Classics are run. At the end of April our younger horse is exactly 2 years old in real time, even though on racing time it's birthday was some four months earlier. Its human comparator is celebrating her 17th birthday. But our earlier foal is now well past its 18th birthday.
We'll all spend some time over the next month or two reflecting on last year's top two-year-old races and wondering which of the participants will mature into Classic winners in their second season. We'll do well to remember that the date the horse was foaled can have quite a bearing on that.