Infants are likely to reach motor milestones at different ages depending on the culture. This is probably due to

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Quizplus · Accepted Answer

The variation in motor milestone timing across cultures is likely due to differences in activity opportunities and physical manipulation. For example, cultures where infants are carried more often or given more opportunities for tummy time may reach motor milestones earlier than cultures where infants are placed in stationary environments for longer periods of time. Climate and nutrition may have some influence, but are less likely to be the sole explanation for such variation. Genetic inheritance alone is also unlikely to explain the cultural differences observed in motor milestone timing.

Infants Are Likely to Reach Motor Milestones at Different Ages