Primeval refers to resembling the earliest stages of something, mainly the world and history thereof. In this instance, the speaker wants to take those steps back to the beginning with a goal in mind. Based on the racial turmoil occurring, the goal can be to start over and hope for a new and improved today. Through this line, Mina Loy's vigilance in racial expression is seen outright. Taking the "lethargic ecstasy of steps" to this goal is slow, but can be worthwhile.