Why do little children run everywhere instead of walking? Is it a legacy of sabre-toothed predators? (continued)
Ibrahim Gasim Ibrahim Ahfad University for Women, Omdurman, Sudan
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When humans evolved into full bipeds, they would be constantly on the move. As there was no birth control, mothers would have several children in tandem. The result was that, as families grew larger, the younger members of the group would have to run to avoid being left behind 鈥� or so they believed.
This trend of running and chasing the older members of the child鈥檚 group stuck with modern humans. Thus, most children today will run and chase around believing they need to catch up.
Toby Pereira Rayne, Essex, UK
One reason not mentioned in previous answers (2 July) is that smaller animals (including little children) are more agile than larger ones because of the cube-square law.
鈥淯sing a compass for navigation has its problems, particularly at the poles or if you switch between hemispheres鈥�
In simple terms, as animals grow, you would expect their mass to increase in proportion to the cube of their linear dimensions (such as length or height). But the cross-sectional area of their legs (a proxy for leg strength) would only increase in proportion to the square of their linear dimensions.
This would result in a deficit of leg strength in larger animals, so, in reality, they don鈥檛 scale up proportionally in this way, and larger animals have relatively thicker legs.
But this all comes at a cost. In the ensuing trade-off, larger animals tend to be less agile than smaller ones, and running becomes more of an effort. Little children don鈥檛 need big, muscly legs in order to run everywhere easily, whereas adults do.
Tony Chabot Birmingham, UK
It is relatively easy to balance a metre rule on a finger, yet a pencil similarly balanced requires small, rapid adjustments. Perhaps small children run so they don鈥檛 fall.
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