Final answer:
Newborn reflexes are inborn responses essential for a baby's early survival, such as the rooting and sucking reflexes. These reflexes are not under conscious control and disappear as the cortex matures, with some, like the Babinski reflex, being abnormal if present in adults.
Step-by-step explanation:
Newborn reflexes are inborn automatic responses that are crucial for a baby’s survival. These reflexes develop during the prenatal period and are fully functional at birth. Reflexes such as the rooting reflex, which directs a baby toward a food source when his or her cheek is touched, and the sucking reflex, essential for feeding, are present from the moment of birth. The grasping reflex and the Moro reflex are also vital for survival, helping the infant to maintain close physical contact with the caregiver.
These inborn reflexes are under subconscious control and are not voluntary; they occur automatically in response to certain stimuli. As the infant's cortex matures, many of these reflexes begin to disappear, usually around 4-5 months old, as the infant develops more complex motor skills and no longer needs these primitive reflexes for survival. In addition to their survival advantage, newborn reflexes also signal normal brain and nerve development.
The Babinski reflex, however, is an example of a reflex that, while normal in infants, can indicate neural problems in adults. In adults, this reflex could be a symptom of reduced myelination of the spinal tract, which can impact their motor skills and sensory processing. Therefore, reflexes that provide survival advantages in infancy can become problematic if they persist into adulthood, demonstrating the evolutionary adaption of human development.