Pronoun problem

pronoun problem

The passage below is from ‘the Blank Slate’ by Steven Pinker.

http://evolbiol.ru/blankslate/blankslate.htm

How this happens is still largely a mystery, but we know that patterns of neural stimulation can trigger the expression of a gene and that one gene can trigger many others. Since every brain cell contains a complete genetic program, the machinery exists, in principle, for neural activity to trigger the development of an innately organized neural circuitry in any of several different regions. If so, brain activity would not be sculpting the brain; it would merely be telling the genome where in the brain a certain neural circuit should go.

I'd like to ask what the underlined 'it' stands for.
It seems to refer to 'brain activity'.
Am I right?

Regards.