HOST: This series is about evolution. But what is evolution anyway? Here's a good first approximation.
In the broadest sense, evolution can be defined as change over time. We all perceive the world around us changing, but we also tend to think that underneath all that change, the world stays fundamentally the same. But evolutionary change, like the flow of time itself, is inescapable and irreversible. It goes deep, all the way to the heart of things and changes them fundamentally and permanently.
The idea of deep evolutionary change began in a place called Ionia, the coastline of what is now Western Turkey and the islands between it and the Greek mainland. There for the first time in human history, people began to formulate naturalistic explanations for the world around them. Democritus of Abdera, who lived in the fifth century BC, was one of the first natural philosophers. He formulated two revolutionary principles that still guide the way we do science. All things are the fruit of chance and necessity, and nothing exists except atoms and the void.
2,500 years before physicists confirmed the existence of atoms, Democritus proposed that all things in the universe are composed of tiny indivisible particles completely surrounded by empty space. He also proposed that all things that happen in the universe are the result of a combination of chance and necessity. That is, that all things are explainable as the result of purely natural causes.
Almost a half millennium later, a Roman philosopher and poet named Lucretius wrote a long poem entitled De rerum natura, which means on the nature of things. In it, Lucretius asserted that everything we know about the universe around us, we know because of observation. Sense data is the basis of all knowledge. This idea now called empiricism is the basis for all of the natural sciences. Lucretius also proposed that a process like natural selection explained the origin of the animals and plants we see around us.
"For [those] creatures thou beholdest breathing the breath of life the same have been... Preserved alive by cunning, or by valor, or... by speed of foot or wing but those beasts to whom Nature has granted non of these same things... Nature [hath] reduced that stock to utter death.
But something happened in between the time of Democritus and today, something that retarded the advance of science for many centuries.
That something was the development of Platonic philosophy as elaborated by the most famous philosopher of all Plato. To Plato, the world of nature that we perceive is not reality at all. Instead, the truest reality can only be found in what Plato called ideal forms. These were ideas that were related to natural objects but existed in the mind of the demiurge, what we would now call God, rather than in nature. And to Plato, these ideal forms were eternal and unchanging.
Aristotle was Plato's most famous student and the founder of what we now call natural history. Unlike Plato, Aristotle believed that the things we could perceive around us were real and that we could understand where they came from and how they worked by observing them. Aristotle also formalized the study of natural history that we now equate with science. He proposed that all things have four causes-- material causes, efficient causes, formal causes, and final causes.
The first two are the causes that most scientists today still use to explain the origin and function of all natural objects and processes. Material causes, what a thing is made of. This rock is made of limestone. Efficient causes, what made the thing. This rock was made as the result of the deposition of the bodies of tiny microscopic organisms and particles of dirt and rock and so forth that were crushed underground by immense forces and eventually became stone such as this.
Finally, Aristotle also argued that all things exist for a purpose. Final causes are the purposes that things exist for. For example, I could use this rock as a paper weight or as a very heavy baseball. That is, this rock has a purpose, but according to Aristotle, all things have purposes. Aristotle also proposed the form of logic, deductive reasoning in which evidence plays very little role. Instead, logicians simply make assertions and then formulate consequences of those assertions without necessarily showing that the assertions themselves are true.
Then in 1620, the English philosopher and scientist Francis Bacon published Novum Organum, his response to Aristotle. Like Lucretius, Bacon argued that the best way to learn about nature is to observe it and to formulate explanations for natural processes based on those observations. Newton proposed that natural objects could be analyzed as if they were made of tiny indestructible objects that collided and rebounded from each other in very predictable ways.
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Published 150 years ago, Charles Darwin's
On the Origin of Species provided the foundation for the modern science of biology. It also set in motion a revolution in the sciences and in our understanding of ourselves and our place in nature.
This CyberTower Study Room is a brief introduction to Darwin's theory and its implications. Beginning with an overview of Darwin's predecessors, we learn how Jean Baptiste Lamarck set the stage for Darwin's monumental achievement with his Philosophie Zoologique, which advanced a theory of evolution by means of the inheritance of acquired characteristics.
Darwin, whose academic training at Cambridge University was in Anglican theology, became an acclaimed naturalist and science writer following the five-year voyage of HMS Beagle. Using the notes and specimens that he had collected during the voyage, Darwin spent twenty years refining his theory, first published in 1859, of evolution by natural selection.
In the last segment of this Study Room, we visit the Museum of the Earth in Ithaca, New York, whose director, Dr. Warren Allman, discusses the importance of such museums to the science of evolutionary biology. We also hear from Cornell professor William Provine, who discusses Darwin's work and its importance to the history and philosophy of biology.
This video is part 2 of 6 in the Darwinian Revolutions series.