Final answer:
Babies recognize key vowel and consonant sounds of their native language by the age of 6 months old, with language skills progressively developing and focusing on their environmental language sounds by 12 months.
Step-by-step explanation:
Babies begin to recognize key vowel and consonant sounds of their native language by 6 months old. This early language recognition is part of a critical period for language acquisition where babies can differentiate between the sounds of all human languages. By 12 months, infants are typically saying their first words, and the ability to discriminate sounds starts to focus only on the phonemes present in their environment. Gesture usage is also a predictor of subsequent language development, and around 6 months, babies may begin to produce two-syllable sounds such as "mama" or "dada". It's important to note that these milestones can vary with each child, but they follow a general pattern of developmental progress in language skills.