Does a newborn baby have a circadian clock? Is a newborn clock different from an adult clock? Physiologically, how might these differences be explained? Are these differences found across species or only in humans?

From the perspective of a chronobiologist consider:

Does a newborn baby have a circadian clock? Is a newborn clock different from an adult clock? Physiologically, how might these differences be explained? Are these differences found across species or only in humans?