Our cosmic-evolutionary scenario is really taking shape now. From stellar atoms to planetary molecules, we have explored plausible ways that galaxies, stars, planets, and life can be surveyed, in turn, along a single range of flowing energy and rising complexity. Indeed, the origin of life seems to be a natural consequence of the evolution of matter, and, further in turn, the evolution of that life a natural process of yet more change with time.

To grasp the entire spectacle of life—from past to present, from aardvark to zucchini—we must inquire beyond specialized reductionism and its specialized analyses of simple matter. Single cells are sufficient to display the operational difference between life and nonlife, but these are not enough to illuminate the full expanse of all life on Earth. To appreciate life’s true complexity—including its structure, function, and diversity—we need to examine whole organisms, generally and often in the context of wider populations. For the same reason that no one could possibly understand the inner workings of an automobile by grinding it up and chemically measuring its basic atoms and molecules, holistic inquiries of entire living things usefully complement microscopic views of their component cells. And if microscopic studies of life forms comprise mainly the realm of chemistry as in the previous CHEMICAL EPOCH, then their macroscopic studies fall squarely into the realm of biology, hence the arrival of the present BIOLOGICAL EPOCH, at least on Earth.

Here, we encounter the vast ensemble of plants and animals on our planet. Roses and reindeer, tulips and turtles, evergreens and elephants, uncounted more species. Where did they all come from? That they suddenly appeared intact from nothing is an interesting idea, but spontaneous or miraculous creation makes no sense scientifically, nor is there a shred of objective evidence to support it.

Together, genes and fossils chronicle an amazing story of life on Earth. Biochemists who amass digital genomes are now pooling their talents with paleontologists who scour fossilized bones. The result is increasingly robust details of that story, regularly revealing torn and tattered pages here, occasionally uncovering whole new chapters there. Repeatedly, throughout millions of millennia, life forms emerged while others perished. Some species survived for ages; others succumbed as soon as they appeared. Incredibly, >99% of all life forms that once prospered are now extinct—victims of the strides of time.

Only one factor has seemingly remained constant and unchanging throughout the eons of Earth’s deep history: change itself. The phenomenon of change really does seem to have been the hallmark in the origin, evolution, development, and fate of all structures, living or nonliving.

The learning goals for this epoch are:

• to sense the blurred time domain between chemical and biological evolution
• to understand what the ancient fossils tell us about the oldest forms of life on Earth
• to appreciate the rich, diverse, and extreme forms of life throughout Nature
• to understand how the recent fossils support the modern theory of biological evolution
• to know the roles played by genetic mutation and environmental change in neo-Darwinism
• to sample the long evolutionary path that led from simple cells to advanced primates
• to realize the early steps in the evolution of the brain on the road to intelligence.