I'm studying the source code Bitcoin, and have no clue to this question.
It looks like the genesis block is mined "out-of-band" (given a timestamp, and a message with no transaction information) and then hard coded into the source code before compiled (with the nonce, hash, Merkle Tree Root hash, and a modified timestamp if no nonce found with the original one). After Googling, it is said that 50 BTC was mined in the genesis block, is the 50 set by the Bitcoin protocol? And will the "50 BTC" message participates in the mining of the genesis block? (No from my current understanding). If the "50BTC" not part of the message for genesis block generation, we're free to change it to, e.g 500BTC after mining the genesis block, and I think that will not violate the original Bitcoin protocol. With this question pending, I am not sure how the first Bitcoin is created (looks out-of-band with the generation of genesis block).
Any hints will be highly appreciated!