Big History – Life and Human Evolution
Meeting 4
The goal of today’s class is to gain an historical perspective on the conditions that led to life on Earth and how over the following 3.8 billion years ultimately delivered Homo Sapiens, the only known species possessing reflective, self-aware consciousness. This is a big story so I will focus on key elements and speed through a lot of interesting detail. To fill in some of the gaps I encourage you to watch three Crash Course episodes I have used in the past. They are light-hearted romps by the Green brothers through key periods of Big History, as described below.
We will start with the formation of the Earth and our Moon, and how the Earth settled into a differentiated structure with a hot iron core, fueling a convective engine that both drives plate tectonics as well as generating Earth’s protective magnetic field. Then we will examine theories about how life originated on the Earth and its earliest form. I do not plan to spend class time on how DNA / RNA work except to address how they may have evolved. This video will touch on the matter and provides a good introduction to the main topics we will cover regarding development of early life.
Then we track the development of life on Earth from the single cell prokaryotes (no nucleus) through the development of eukaryotes and multicellular plant and animal life over the course of ~3 billion years. This video is a nice introduction, which – following a description of the conventional theory of evolution – takes you on a breakneck ride through the entire evolutionary sequence up to the rise of mammals and the entry of primates on Earth’s biological stage.
Finally, we follow evolution from the Last Common Ancestor of hominids to the rise of Homo sapiens through the Modern Era. An explanation of the early evolutionary path of Great Apes leading to H. sapiens and their early progress in collective learning as hunter-gatherers is captured quite nicely in this video, which ends with the near-extinction event 74 kYA due to the volcanic eruption of Mt. Tobo in Sumatra that reduced the human race to a few thousand people. The Green brothers also spend some time on what they call the Hobbes-Rousseau debate on the nature of human beings, which we will also briefly discuss. We will conclude the class with the discussion of how the agriculture revolution about 12,000 years ago transformed how human beings lived in small hunter-gather tribes to large cities organized to house, feed and protect its citizens.
