ANTA01H3 Chapter Notes - Chapter 2: Scientific Revolution, Intelligent Design, Pope Urban Viii
Chapter 2: The Development of Evolutionary Theory
2-1 A Brief History of Evolutionary Thought
• Charles Darwin was the first person to explain the basic mechanics of the
evolutionary process. But while he was developing his theory of natural
selection, a Scottish naturalist named Alfred Russel Wallace independently
reached the same conclusion. That natural selection, the single most important
force of evolutionary change, was proposed at more or less the same time by two
British men in the mid-nineteenth century may seem like a strange but if Darwin
and Wallace hadn’t made their simultaneous discoveries, someone else soon
would have, and that someone would probably have been British or French. That’s
because the groundwork had already been laid in Britain and France, and many
scientists there were prepared to accept explanations of biological change that
would have been unacceptable even 25 years before.
• Throughout the Middle Ages, one predominant feature of the European worldview was that
all aspects of nature, including all forms of life and their relationships to one another, never
changed. This view was partly shaped by a feudal society that was itself a rigid class system
that hadn’t changed much for centuries. But the most important influence was an extremely
powerful religious system in which the teachings of Christianity were held to be the only
“truth.” Consequently, it was generally accepted that all life on earth had been created by
God exactly as it existed in the present, and this belief that life-forms couldn’t and didn’t
change came to be known as fixity of species. Anyone who questioned these notions of
fixity, especially in the fifteenth and sixteenth centuries, could be accused of challenging
God’s perfection, and that was heresy. Generally, it was a good idea to avoid accusations of
heresy because it was a crime punishable by trial by fire (a nasty, fiery death).
• The plan of the entire universe was viewed as God’s design. In what is called the “argument
from design,” anatomical structures were engineered to meet the purpose for which they
were required. Limbs, internal organs, and eyes all fit the functions they performed; and
they, along with the rest of nature, were a deliberate plan of the Grand Designer. Also, the
Grand Designer was thought to have completed his works as recently as 4004 B.C. The
prevailing notion of the earth’s brief existence, together with fixity of species, was a huge
obstacle to the development of evolutionary theory. Until the concepts of fixity and time were
fundamentally altered, it was simply not possible to conceive of evolution by means of
natural selection.
2-1a The Scientific Revolution
• For Europeans, the discovery of the New World and circumnavigation of the globe in the
fifteenth century overturned some very basic ideas about the planet. The earth could no
longer be thought of as flat. Also, as Europeans began to explore the New World, their
awareness of biological diversity was expanded as they encountered plants and animals
they’d never seen before.
• There were other attacks on traditional beliefs. In 1514, a Polish mathematician named
Copernicus challenged a notion proposed more than 1,500 years earlier by the fourth-
century B.C. Greek philosopher Aristotle. Aristotle had taught that the sun and planets
existed in a series of concentric spheres that revolved around the earth. This system of
planetary spheres was, in turn, surrounded by the stars. This meant, of course, that the
earth was the center of the solar system. In fact, scholars in India had figured out that the
earth orbited the sun long before Copernicus did; but Copernicus is generally credited with
changing the idea that the earth was the center of the universe.
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• Copernicus’ theory was discussed in intellectual circles, but it didn’t attract much
attention from the Catholic Church. (Catholicism was the only form of Christianity
until the 1520s.) Nevertheless, the theory did contradict a major premise of church
doctrine, which at that time wholeheartedly embraced the teachings of Aristotle.
By the 1300s, the church had accepted these teachings as dogma because they
reinforced the notion that the earth, and the humans on it, were the central focus
of God’s creation and must therefore have a central position in the solar system.
• However, in the early 1600s, an Italian mathematician named Galileo Galilei
restated Copernicus’ views, using logic and mathematics to support his claim. To
his misfortune, Galileo was eventually confronted by the highest-ranking officials
of the Catholic Church (including his former friend, Pope Urban VIII), and had to
face the Roman Inquisition (the court of justice associated with the church). He
spent the last nine years of his life under house arrest, but continued to publish
scientific works (outside of Italy) that were far less controversial. Nevertheless, in
intellectual circles, the solar system had changed; the sun was now at its center,
and the earth and other planets revolved around it as the entire system journeyed
through space.
• Throughout the sixteenth and seventeenth centuries, European scientists
developed other methods and theories that revolutionized scientific thought. In the
seventeenth century, the discovery of the principles of physics (such as motion
and gravity) and the invention of numerous scientific instruments, including the
microscope. These advances permitted the investigation of many previously
misunderstood natural phenomena. Even with these advances, the idea that living
forms could change over time simply didn’t occur to people.
2-1b Precursors to the Theory of Evolution
• The concept of species wasn’t proposed until the seventeenth century, when John Ray, a
minister educated at the University of Cambridge, developed it. He recognized that groups
of plants and animals could be differentiated from other groups by their ability to mate with
one another and produce fertile offspring. He placed such groups of reproductively
isolated organisms into categories, which he called species. By the late 1600s, the
biological criterion of reproduction was used to define species, much as it is today. Ray also
recognized that species frequently share similarities with other species, and he grouped
these together in a second level of classification he called the genus (pl., genera). He was
the first to use the labels genus and species in this way. We still use these terms today.
• Carolus Linnaeus (1707–1778) was a Swedish naturalist who developed a method of
classifying plants and animals. In his famous work, Systema Naturae (System of Nature),
first published in 1735, he standardized Ray’s use of genus and species terminology and
established the system of binomial nomenclature. He also added two more categories:
class and order. Linnaeus’ four-level system became the basis for taxonomy, the system of
classification we continue to use.
• Linnaeus also included humans in his classification of animals, placing them in the
genus Homo and species sapiens. (Genus and species names are always italicized or
underlined.) Including humans in this scheme was controversial because it defied
contemporary thought that humans, made in God’s image, should be considered unique and
separate from the rest of the animal kingdom. Linnaeus also originally classified whales as
fish; however, he later changed his mind and reclassified them as mammals based on their
anatomical features (a controversial idea at the time).
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• Linnaeus still believed in fixity of species, although in later years, faced with mounting
evidence to the contrary, he came to question it. Indeed, fixity was being challenged on
many fronts, especially in France, where voices were being raised in favor of a universe
based on change and, more to the point, in favor of a biological relationship between similar
species based on descent from a common ancestor.
• A French naturalist, Georges-Louis Leclerc, Comte de Buffon (1707–1788), recognized the
dynamic relationship between the external environment and living forms. In his 36-
volume Histoire Naturelle (Natural History), first published in 1749, he recognized that
different regions have unique plants and animals. He also stressed that animals had come
from a “center of origin,” but he never discussed the diversification of life over time. Buffon
recognized that alterations of the external environment, including the climate, were agents of
change in species. For this reason, the twentieth-century evolutionary biologist Ernst Mayr
said of him: “He was not an evolutionist, yet he was the father of evolutionism”
• Erasmus Darwin (1731–1802) is best known as Charles Darwin’s grandfather. But he was
also a physician, a poet, and a leading member of an important intellectual community in
England. In fact, Darwin counted among his friends some of the leading figures of the
industrial revolution, a time of rapid technological and social change. In his most famous
poem, Darwin expressed the view that life had originated in the seas and that all species
had descended from a common ancestor. Thus, he introduced many of the ideas that his
grandson would propose 56 years later. These concepts include vast expanses of time for
life to evolve, competition for resources, and the importance of the environment in
evolutionary processes. From letters and other sources, we know that Charles Darwin read
his grandfather’s writings, but we don’t know how much he was influenced by them.
• Neither Buffon nor Erasmus Darwin attempted to explain the evolutionary process,
but a French naturalist named Jean-Baptiste Lamarck (1744–1829) did. Lamarck
suggested a dynamic relationship between species and the environment such that
if the external environment changed, an animal’s activity patterns would also
change to accommodate the new circumstances. This would result in the
increased or decreased use of certain body parts (that is, “use it or lose it”);
consequently, those body parts would be modified. According to Lamarck, the
parts that weren’t used would disappear over time. However, the parts that
continued to be used, perhaps in different ways, would change. Such physical
changes would occur in response to bodily “needs,” so that if a particular part of
the body felt a certain need, “fluids and forces” would be directed to that point, and
the structure would be modified. Because the alteration would make the animal
better suited to its habitat, the new trait would be passed on to offspring. This
theory is known as the inheritance of acquired characteristics, or the use-
disuse theory.
• One of the most frequently given hypothetical examples of Lamarck’s theory is the giraffe,
which, having stripped all the leaves from the lower branches of a tree (environmental
change), tries to reach leaves on upper branches. As “vital forces” move to tissues of the
neck, it becomes slightly longer, and the giraffe can reach higher. The longer neck is then
transmitted to offspring, with the eventual result that all giraffes have longer necks than did
their predecessors. So, according to this theory, a trait acquired by an animal during its
lifetime can be passed on to offspring. Today we know that this explanation is wrong
because only those traits that are influenced by genetic information contained within sex
cells (eggs and sperm) can be inherited.
• Because Lamarck’s explanation of species change was incorrect on a genetic
level, he is frequently scorned even today. But in fact, Lamarck deserves a great
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Document Summary
2-1 a brief history of evolutionary thought: charles darwin was the first person to explain the basic mechanics of the evolutionary process. But while he was developing his theory of natural selection, a scottish naturalist named alfred russel wallace independently reached the same conclusion. That natural selection, the single most important force of evolutionary change, was proposed at more or less the same time by two. British men in the mid-nineteenth century may seem like a strange but if darwin and wallace hadn"t made their simultaneous discoveries, someone else soon would have, and that someone would probably have been british or french. This view was partly shaped by a feudal society that was itself a rigid class system that hadn"t changed much for centuries. But the most important influence was an extremely powerful religious system in which the teachings of christianity were held to be the only.
