Motherwell had the youngest team in the Scottish Premiership last season, while Kilmarnock had the oldest.
According to analysis from Swiss-based research group CIES Football Observatory, the Steelemen, who relied heavily on youngsters David Turnbull, Jake Hastie and Allan Campbell, had an average age of 25.45 years.
That was just ahead of Aberdeen at 25.83, while league champions Celtic were the fifth youngest at 26.4.
Kilmarnock had the oldest mean age at 27.71, just behind Hibs (27.31) and Rangers (27.13)
CIES looked into Europe’s top 31 leagues and found the the Scottish top-flight collectively had the 14th lowest average age at 26.58.
The lowest was Croatia at 24.77 and the highest Turkey at 28.99.
England were 21st at 27.17.
Turkish side Istanbul Basaksehir also had the oldest age at 30.91, with Danish team Nordsjaelland the youngest at 21.58.
St Mirren: 25.99
St Johnstone: 26.91