Yes, definitely. Dr Steph Croxford is a Grand Prix dressage rider, and didn't get on a horse until she was 24 ! She has buckets of natural ability, and she's managed to get to the top on a horse that most dressage riders wouldn't have looked at twice (Mr President). I think she's utterly fab.
Conversely, there are some riders (i.e me.) who've been riding since they were small, and are STILL rubbish !!!
I'm hoping so. Secretly wish to become a top dressage rider later in life when I have sufficent money to afford a proper dressage horse (rather than making my poor jumping cob continue to suffer under my dressage desires!)
What about Hinrich "the dentist" Romeike and Marius his horse, double gold winner at the olympics who still works as a dentist during the week (human one, not EDT) didn't he start late?
An example is Paul Schockemohle started as an adult, finally following in the footsteps of his much more naturally talented older brother Alwin.
The few who are blessed with great natural talent e.g. David Broome, John Whitaker can improve their skills (mostly tactical I think) over time. With horses of equal ability they will always have the edge over the others who have had to learn far more. It also means they are not so likely to make the best instructors as it's hard to explain to pupils something that comes completely naturally to you.
Wow just looked up some stuff on Dr Steph Croxford - really inspiring! I started riding about 4 1/2 years ago whne I was 23 and I sometimes wonder what (if anything) I should aim for with my cob as I alway though that coming into riding later in life would alway hold me back but it just shows you what can be achieved!
I have actually been told by many instructors that i have a natural riding talent- however the lack of confidence that overtakes it ruins any chances i have.
As far as I am aware Ian Stark (who was an Olympic event rider for those younger users!) didn't start riding until in his late twenties. Could be wrong re exact age but he did only start as an adult.