There seems no reason to doubt the most widely accepted theory, that in play the young of any species rehearse and practise the activities which they will have to perform in earnest later on. ... They enjoy anything that gives them new muscular facilities, such as jumping, climbing, or walking up a narrow plank--always provided the task is not too difficult.
Source: On Education, especially in early childhood, 1926, by Bertrand Russell
More info.: https://russell-j.com/beginner/OE05-010.HTM
* a brief comment:
Not only human children, but the young of all species, try to acquire various abilities through play, driven by a desire to become able, as soon as possible, to do what adults can do.
It is often said that "play is the work of the child," and this can be seen as an expression of the natural impulse children have to grow and develop quickly.
The abilities individuals wish to acquire vary -- physical strength, intellectual capacity, imagination, and more. However, the specific abilities they actually develop often depend on which adults are around them or whom they admire.
When it comes to intelligence and imagination, if the person a child models themselves on is admirable, the abilities they acquire are likely to be those valued by society. Conversely, if the role model is not admirable, the resulting traits are often viewed negatively by others.
For example, a figure like President Donald Trump may serve as a "negative role model" but it remains doubtful how effective that actually is in practice.
The following quote from "Russell's Words for Today" concerns physical strength. With the exception of cases where strength is used for violence, such as in criminal acts, it is generally regarded as a desirable ability.
"There seems no reason to doubt the most widely accepted theory, that in play the young of any species rehearse and practise the activities which they will have to perform in earnest later on. ... They enjoy anything that gives them new muscular facilities, such as jumping, climbing, or walking up a narrow plank?always provided the task is not too difficult."
