Orc

Orcs did not evolve, they were created. When the Dragon Laku needed an army, he took it upon himself to manipulate the people living on Ilor, making them bigger, strong and more aggressive.
After he was defeated and the war over, the people did not change back, the damage could not be undone. And as the years went by their children beared the curse their forefathers were given. Due to their aggressive nature, they became fractured with Laku's defeat, splitting into small factions and fighting others.
In the centuries since the war, the aggressive tendencies have mellowed dramatically, and though still present, and they are well on the path to collectivising and creating stronger civilisation. Currently, this has manifested in nation states of large size but low density in cold wars over Ideals and the future of their race.