Riddle: I have 4 legs in the morning, 2 in the afternoon and 3 in the night. What am I?
Morning describes the earliest period of human life, at the time the humans are infants and they walk with four legs. Humans are walking with two legs in the afternoon and it defines the mid-stages of life.
Night refers to the end stages of life and humans walk with three legs in the night, the third leg is a cane. So instead of thinking of the literal meanings of the morning, afternoon, and night we need to take their metaphorical meanings into consideration.
Answer: A human.