The first value in the Agile Manifesto is Individuals and interactions over processes and tools. It reminds us that programming is a human activity. For example, XP champions the importance of happy developers for sustainable development. Mindful of the impact of overwork on the ability to program well or maintain a healthy social or family life, XP has the rule of sustainable pace avoiding working overtime. Agile Principle 8 states, Agile processes promote sustainable development.
Also, research shows that individual developer contributions vary enormously, with studies illustrating 10 times more productive from best to worst [Boehm81]. This does not imply promotion of (unsustainable) heroic individual programming, but the right knowledge and work habits play a significant productivity role thus the value of ongoing education and mentoring for developers. XP encourages deep skills transfer through the practice of pair programming.
The primacy of people and interactions over process is also promoted in agile methods by their emphasis on communication, especially face-to-face conversations. Scrum's daily meeting and common project room, and XP's pair programming and whole team together are examples.