"The Million-Year Picnic" is the last story in The Martian Chronicles, detailing how a family steals a rocket from the government and flees the nuclear wars on Earth to settle on Mars. Throughout the story, a sense of fear can be seen in the words and behavior of the Father, who knows that Earth is doomed. His children believe that they are on vacation, a picnic on Mars, and only later is it fully understood that the nuclear wars have devastated life on Earth, leaving barely anyone alive. The theme of Man versus Technology is subtle, but can be seen as the Father destroys his own rocket in order to cover their tracks. He has seen the rise of technology, specifically destructive technology, and believes that the only way his family will survive is to abandon their previous way of life and literally become the new Martians.
"Science ran too far ahead of us too quickly, and the people got lost in a mechanical wilderness, like children making over pretty things, gadgets, helicopters, rockets; emphasizing the wrong items, emphasizing machines instead of how to run the machines."
(Bradbury, The Martian Chronicles, Google Books)
The immediate point is that humanity developed their weapons of mass destruction, which led inevitably to their use against other humans, resulting in mutually-assured destruction. The deeper point is that humanity simply progressed too quickly in their sciences, without equal development in moral responsibility; just because they could develop their weapons didn't mean that they needed to. Humanity was given the power to destroy without the corresponding ability to understand what that power truly meant. Because their reach exceeded their grasp, humanity destroyed itself; the development of technology shouldn't occur outside of the development of personal and moral responsibility, and full understanding of consequences.