hormones and receptors - what came first?

first, i will start and say that i am evolutionist.How does evolution could explain the emergence of new hormones and their receptors?hormone by definition is : Chemical messenger from one cell (or group of cells) to another.receptor by definition is: Protein molecule that receives and responds to a specific neurotransmitter, hormone, or other substance.both receptors and hormones are coded in the DNA.The function of many proteins is to interact specifically with other molecules in tightly integrated regulatory systems. When the function of each part depends on the prior existence of all the other parts, the Darwinian model seems to breaks down.What's the selective pressure that drives the evolution of a new hormone if there's not already a receptor to give it a function? Conversely, how does a new receptor evolve unless there's a hormone present?

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