Final answer:
Motor development in infancy depends on both the nature, which includes genetics and biological factors, and nurture, which involves the environmental influences and cultural practices that can impact the timing and achievement of motor skill milestones.
Step-by-step explanation:
Motor development in infancy relies on two core developmental processes: nature and nurture. The aspect of nature includes genetic factors and biological conditions, such as newborn reflexes like the Moro reflex and the grasping reflex, which are innate and help with immediate post-birth adaptation. Nurture, on the other hand, encompasses the environmental influence and child care practices that can vary culturally and affect the timing and acquisition of motor skill milestones like sitting, crawling, and walking.
Motor skills are the capabilities enabling movement and manipulation of objects and are divided into fine and gross motor skills. Fine motor skills involve smaller actions by using muscles in fingers, toes, and eyes, while gross motor skills involve larger movements like balancing and running, utilizing larger muscle groups.
While there is a universal sequence to milestone development, cultural factors can lead to variation in the pace at which these milestones are reached. This illustrates the interplay between a child's genetics and their environment, shaping the course of their development.