A world where tropical forests stretched across a warmer planet

Space · Published 31 October 2026 Swipe more like this →

In short: Imagine an Earth significantly hotter than our own, where the continents sat closer together to create vast corridors for life. This was the Eocene Epoch—the dawn of the modern world where primates first appeared and ancient giants began their evolutionary journey.

The Eocene Epoch spanned from 56 to 33.9 million years ago, serving as the first epoch of the Cenozoic Era. This period was defined by a climate that was much warmer than today's, with temperatures reaching up to 10°C higher in some regions. These elevated temperatures facilitated the global spread of tropical and subtropical flora and fauna, creating a lush environment that differed drastically from our current ecological landscape. This era followed the Paleocene and preceded the Oligocene. It represented a major worldwide division of the Paleogene Period.

Geologically, the Eocene was a time of significant transition for the Earth's surface. Because the continents were positioned much closer to one another than they are in the present day, species were able to disperse more easily across land and sea. This proximity allowed for the emergence and migration of iconic lineages, including the first primates, as well as early ancestors of modern horses and elephants. During this time, the first modern plants also began to appear. These biological developments marked the start of our modern day world.

While the Eocene provided the stage for these biological milestones, it was also shaped by the fundamental mechanics of plate tectonics. The theory, which gained universal acceptance in the 1960s, explains how the Earth's lithosphere—a rigid outer layer about 100 km thick—is broken into large and small plates. These plates move at rates of 5 to 10 cm per year over a plastic asthenosphere, driving the mountain-building, volcanic activity, and continental drifting that ultimately sculpted the modern geography we see today. The theory incorporates older concepts like seafloor spreading and continental drift. It provides a framework for understanding how the atmosphere and hydrosphere evolved alongside the crust.

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