1. A method comprising: generating a first plurality of agents, wherein each agent includes a set of ad characteristic definitions ordered in a linear array, wherein each ad characteristic definition includes a set of ad characteristics ordered in a linear array, that define how an ad associated with the respective ad characteristic definition is displayed, and wherein a position of each ad characteristic definition along a linear array of a respective agent determines a respective ad slot within a page layout; sending display information to a user device to display the ad content according to the first plurality of agents; accepting a user input signal associated with the user device to indicate an impact of the ad content upon a human user for each agent of the first plurality; generating a second plurality of agents, wherein each agent of the second plurality of agents includes a set of ad characteristic definitions ordered in a linear array, wherein each ad characteristic definition includes a set of ad characteristics ordered in a linear array, that define how an ad associated with the respective ad characteristic definition is displayed, and wherein each agent of the second plurality of agents is derived at least in part from better-performing agents of the first plurality according to the impact of each agent of the first plurality; determining that a first agent and a second agent are better-performing than at least one other agent, wherein the first agent includes a set of first ad characteristic definitions ordered in a linear array, and wherein the second agent includes a set of second ad characteristic definitions ordered in a linear array; using a first portion of the first agent and a second portion of the second agent to create a third agent, wherein the first portion includes one or more ad characteristic definitions of the first agent, wherein the second portion includes one or more ad characteristic definitions of the second agent, and wherein the third agent includes a combination of ad characteristic definitions from the first and second portions; and sending display information to the user device to display the ad content according to the third agent.