8.1: Developing the Theory of Evolution by Natural Selection
Scientific theories are the result of hard work by many people gathering and analyzing data. The general
process follows steps similar to these:
1. A scientist observe certain patterns and states a hypothesis; and idea that may explain the pattern
but has not been proven.
2. Experiments are done and more data is gathered and analyzed to see if it supports or refutes the
hypothesis.
3. If significant data from several groups of researchers supports the hypothesis, then it becomes a
theory; a coherent explanation for observations about the natural world.
If data refutes the hypothesis, then the hypothesis is often revised to take the data into account. In this
way, many people over many centuries worked together to advance our understanding of the natural
world.
Today’s theory of evolution is the result of centuries of research by many scientists, each one building
on the work of others.
Traditional scientific thought, as express by early philosophers such as Plato and Aristotle, was that life
was unchanging because it was already perfected. In 1707-1708, George-Louis Leclerc published Histoire
Naturelle, in which he included the hypothesis that similarities between humans and apes might mean
they had a common ancestor.
Complete Theories Chart.
Charles Darwin used the ideas, readings, and works of Jean-Baptiste Lamarck, Charles Lyell, and Thomas
Malthus, as well as his own observations, to create his theory of evolution by natural selection, which is
accepted today as a guiding theory to explain evolutionary pathways and forces. Alfred Russell Wallace
developed similar theories during the same time period. Their combined paper was published in 1858.
Darwin based his theory of evolution by natural selection on two pillars:
-
An analysis of data gathered by many other scientists that showed life had changed in specific
ways over time.
- His own observations of the distribution of species around the world.
These are the main points of the theory of evolution by natural selection:
1. Members of a population vary (differ from one another). The traits that vary are inheritable.
2. Most populations have more offspring each year than local resources can support, leading to a
struggle for resources. Since the environment cannot support unlimited population growth, not all
individuals get to reproduce to their full potential. The fittest individuals will contribute more
offspring to the next generation. This is the idea of survival of the Fittest, and Darwin called this
natural selection.
3. Natural selection acts on traits that can be passed on from one generation to the next.
4. The process for change is slow and gradual.
Learning Check:
1. Why is evolution by natural selection, considered a theory and not a hypothesis? [k/u]
2. Explain how these three ideas relate to one another, according to Darwin’s theory of evolution by
natural selection. [k/u]
a) survival of the fittest
b) natural selection
c) evolution