At the beginning of the Pennsylvanian Era (320 - 295 mya), when most of the world's coal was forming, moist forests, peat bogs, vast coastal swamps and tidal marshes covered large areas of what would eventually become eastern North America and northern Europe. Contrary to popular notions, true dinosaurs were still millions of years in the future. These great primeval forests were situated in the tropics, immediately north of the equator, and had climates that were warm and humid; seasons were indistinct.  Cockroaches, identical to those found today, were the predominant insects. Tropical conditions promoted the growth of the vegetation and marine organisms which would eventually form coal, oil and gas; the plant life of the time, or at least what has been deduced from the fossil record, exhibits little diversity; the same genera and often the same species are found in widely separated regions. About 2000 species are known from the period, most of them non-flowering, spore-producing plants. Early club mosses, tree-sized lycopods and hydrophilic horsetails, made up much of the Carboniferous forest. Enormous ferns were dominant among the land plants. These terrestrial pioneers and a few others have succesfully reproduced for 325 million years and their descendants are still well established in the sandy hills of the DBNF.

Since soon after the time of the earliest recorded life on earth, about 3.6 billion years ago, the planet's average surface temperature has steadily averaged at about 70° F.  For more than 90 percent of that stretch of time earth has been free of ice ages, and no large glaciers have existed except in high mountains. Ice ages occur about every 150 million years, and last for a few million years. The Carboniferous forests covered the land at a time when temperatures were uniformly tropical and the atmosphere was oxygen rich. A fertile incubator for life in the sea, a green blanket on the land. This period may well have hosted the first Amniotes, an ancient group that includes turtles, lizards, birds, dinosaurs, and mammals. The Amniotes were capable of a revolutionary means of birth; a specialized egg allowing them to reproduce on land by preventing the desiccation of the embryo inside. The amniotic sac in modern day mammals is a remnant of the original design, with yolk sack becoming the placenta plus the added feature of a more versatile eggshell doubling as Mom.

The first true reptiles appeared at this time, developing from earlier amphibians. Corals, crinoids, and minute foraminifers were abundant and there were still a few trilobites and eurypterids crawling around. Snails and mollusks, including cephalopods and nautiloids, were widespread. Horseshoe crabs and large salamander like creatures moved through the creeks. Polyzoa and brachiopods of all kinds were common, as were sharks and primitive, hard-scaled fish. Life was thriving in the seas. Scorpions had already been around for one hundred million years. Insects were very common.  Life on the land was already well accomplished; animals began taking to the air.  Monstrous six foot millipedes slithered through the undergrowth and dragonflies as big as hawks cruised the tropical rain forests of the Carboniferous era.  Plenty of carbon bonding in all those organic cells. The rich expanse of Carboniferous flora and fauna was transformed into great black beds, milllions of generations of ancient forests compressed deep in the earth into thick seams of crystalized fire.

40-34  million years ago, the earth underwent global cooling and drying and the first signs of Antarctic glaciation appeared. The radical reorganization of oceanic and atmospheric circulation changed vegetation and climate throughout the world. These changes, in turn, caused mass extinctions in both the marine and terrestrial realm. The average temperature of the earth today is 60°F.  We are on the tail end of an ice age which would account for some of the lowered temperatures, but the cooling has been occuring over a longer period of time.  Among other things, it has been suggested that the upthrusting of the Himalayas over the last 60 milllion years has contributed to an overall drop in global temperatures since the Eocene by leaching carbon from the atmosphere as carbonic acid in snow and rainwater, creating sort of an anti-greenhouse effect.