Biomen are the genetically engineered results of a top-secret project commissioned by the Earth Military Coalition in the year 2000 to combat a potential alien invasion.
It took Earth’s scientists the better part of twenty years to perfect their lab-grown weapons of war. Biomen are tall, huge and heavily muscled. They’re designed to kill and withstand massive amounts of punishment. They can have a variety of skin tones – both natural and unnatural – and possess eyes of vivid color. Every group of Biomen has a “batch name” based on the name of a U.S. president (Reagan, Carter, Woodrow, Barack) and individuals are branded with a unique serial number (Ulysses-537634). 
The armistice between humans and Votans and the dissolution of the Earth Military Coalition effectively rendered Biomen obsolete. The Earth Republic has tried to integrate Biomen units into their security forces with mixed results. Many of them suffer from the same aggression they displayed during the war, and behave erratically when they’re not given something to destroy. For this reason, Biomen are stigmatized by both Votans and humans.
They are not really considered to be a species of their own, as they are genetically engineered humans created to be used as tools. But they are different enough from the average human that most Biomen have trouble integrating with society. Many surviving Biomen want nothing more than to be perceived as normal.
Biomen were designed to be the ultimate killing machine, unburdened by feelings of doubt or remorse. Their creators estimated that most Biomen would perish in the war, and they weren't intended to still be alive long after the war ended. Their stunted sense of morality, coupled with erratic behavior due to their age, means that Biomen in the modern world have the emotional range of a child. 
The biomen shown on the tv series tend to be extremely trusting of their employers, take people at face value, and don't understand when they are being lied too. When Meeko offers to take Ulysses and flee Defiance in A Well Respected Man, Ulysses does not notice all the telltale signs of a lie that most people would notice. Similarly, when Niles Pottinger is in a life or death situation, he sends Churchill into a fight with only a metal bar to defend himself. Although Churchill suspects it will not be enough to defeat the Gulanee, Pottinger easily convinces him it will. Pottinger then tells Churchill he's going to take him out as soon as they get home even though he's being sent on an undeniable suicide mission. Their unfailing loyalty to their employers tends to frequently put them in harms way.
Although they are often overly trusting, they are not incapable of reading between the lines. In Dead Air, Pottinger's bioman, George, can tell that Amanda Rosewater is unhappy around Pottinger. When George doesn't want to leave Pottinger alone with her, Amanda compares him to a jealous ex-girlfriend.
Known Biomen (TV)
Niles Pottinger's loyal bioman in season 2. He serves as Pottinger's assistant during his term as mayor. Churchill handles the "heavy lifting" while also acting as his bodyguard.
George, John, Paul, & Ringo
The four biomen who live with Niles Pottinger in his bunker in season 3 episode 4.
Conrad Von Bach's loyal bodyguard who appears in season 3 episode 7.
- Rob Archer plays the most important biomen in the series, including Ulysses, Churchill, George, and Benedict