With the advancement of micro-sensor and radio technology, wireless sensor networks are deployed in various applications. In a continuous monitoring application, sensors gather information and transmit the sensed data to base station in a periodic manner. In each data gathering round, a node generates a data packet and transmits the packet to base station, or any other node; the data packets received from neighbouring nodes can be aggregated. The lifetime of such sensor system is the time until base station receives data from all sensors in the network. We propose a Genetic Algorithm (GA) based multi-hop routing for a homogeneous network to maximize the network lifetime. Given the location of the sensor nodes and base station, our algorithm generates a sequence of routing paths that maximizes the system lifetime.