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?

as i mentioned in the first post i am an evolutionist..
As i read creationists claims about Irreducible Complexity i got puzzled.let's look on the following Irreducible system:The problem only gets complicated to explain,if we look on the suckle reflex in mammals, a friction sensors on the mother nipples sense the infant sucking, as a result a signal is being sent via neurons from the nipples to the hypothalamus in the brain. after the signal has been processed a signal is being sent to the hypophyses gland.
as a result the hypophyses gland releases two hormones to the blood stream.
the two hormones travels in the blood stream until they reach a specific receptors in a specific cells membranae in the milk glands.
this results two things:
1. the milk is being squeezed.
2. the milk reproduction process is being accelerated.the process could be read here:Human Milk and Lactation: Background, Physiology, Human Milk and Preterm Infanthow could this 'irreducible complexity' system be reduced?each factor is important for this system evolution, the friction sensors is important, the neurons connection to the hypothalamus, the process in the hypothalamus, the signals which is sent from the hypothalamus to the hypophyses gland, the metabolic process which results the manufacture of the two hormones, the proteins in the receptors in the milk glands. and the special processes which accurs after the hormones reach to this receptors.
and all the parts of the system is a result of many genes working together, why would each part develop if another part didn't existed?
why would a friction sensors develop in the nipples if the link between the hypothalamus and the hypophyses didn't existed?
and if the receptors didn't existed? and if the hormones didn't existed?
if the whole course didn't existed why would any of the parts develop separately?This message has been edited by caligola2, 02-02-2005 16:14 AM

thank you for the replay,I accept what you wrote about the mammary glands.Do you an easy way to recognize whether a system is Irreducible Complexity or not?This message has been edited by caligola2, 02-18-2005 15:28 AM

The definition from EvoWiki is: the definition is easy to understand.
But, if i take a system such as the mammary glands as i described. how can i determine whether she is IC or not?will a genetic mapping of the system will give the result?
[if we know that the system needs 7 genes to make her work - could this be a way to determine?]or should i try to find info. on how the system work in other organisms?
[in order to see if variation of the system is possible]This message has been edited by caligola2, 02-18-2005 16:51 AM