Nested Hierarchies, the Order of Nature: Carolus Linnaeus (1 of 2)

Homo sapiens, Tyrannosaurus rex, Escherichia coli—our English conversation is littered with pairs of Latin names for animals, plants, and microbes. How did a dead language find this renewed life? It is the 250-year-old legacy of a Swedish naturalist’s quest to discover God’s handiwork in nature.

Linnaeus

Carolus Linnaeus (1707-1798) was far from the first thinker to try to classify life. Aristotle, for example, argued that each species had a unique form and could be classified by some of its key characteristics. In the process, he organized life in a ladder-like hierarchy, with plants on the bottom, animals in the middle, and humans on top (figure, right). Medieval European scholars were guided by both Aristotle and the Bible, and they believed that nature—including all of the species on Earth—reflected God’s benevolent organization of the world.

Searching for a System of Classification
With the advent of the Renaissance, naturalists tried to understand this divine plan by searching for a rational pattern in the bewildering array of species. They grouped species with an overall similarity with one another in a larger group called a genus. Lions, tigers, and leopards, for example, all belonged to a “big cat” genus.

But did big cats and other animals fit into a larger scheme? This was difficult to know for many reasons. One problem was that European explorers and colonists began encountering many previously unknown species in the New World, Africa, and Asia. On top of that was the problem of method. Some argued that naturalists looking for a system of classification should try to take into account as many characteristics of a species as possible. That would ensure that their classification system was truly natural. Others argued that we do not find systems in nature but construct them in our minds. Therefore naturalists should invent artificial systems based on a few convenient traits of their own choosing, such as the shape of a plant’s reproductive organs.

Aristotle's Great Chain of Being
Linnaeus’ system diverged from Aristotle’s vision of a Great Chain of Being, above.
• Linnaeus image courtesy of the Swedish Museum of Natural History. next page


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Spanish translation of Understanding Evolution For Teachers from the Spanish Society of Evolutionary Biology.