All nutrients and energy are cycled. Although we tend to think that we are less dependent on plants today, this is partly a U.S. bias. This is not true for most people in the world. We are dependent on fewer species of plants than formerly, but even in the U.S. we are highly dependent on plants.
Petroleum is the remains of former plants.
We will talk about domesticated plants, gathered plants, and wild plants. By 2000 years ago, most of the major peoples and regions of the earth practiced agriculture. Almost all of the oldest records are from the Near East. Man was a hunter-gatherer before he began agriculture. In 1900, hunter-gatherers were restricted to small areas that were too dry, too cold or too wet for agriculture.