The Transmission Control Protocol (TCP) protocol, i.e., one of the most used protocols over networks, has a crucial role on the functioning of the Internet. Its performance heavily relies on the management of the congestion window, which regulates the amount of packets that can be transmitted on the network. In this paper, we employ Genetic Programming (GP) for evolving novel congestion policies, encoded as C++ programs. We optimize the function that manages the size of the congestion window in a point-to-point WiFi scenario, by using the NS3 simulator. The results show that, in the protocols discovered by GP, the Additive-Increase-Multiplicative-Decrease principle is exploited differently than in traditional protocols, by using a more aggressive window increasing policy. More importantly, the evolved protocols show an improvement of the throughput of the network of about 5%.