Evolution__3rd_Edition

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Introduction
Part one
When Darwin put forward his theory of evolution by natural selection, he lacked a
satisfactory theory of inheritance, and the importance of natural selection was
widely doubted until it was shown in the 1920s and 1930s how natural selection
could operate with Mendelian inheritance. The two key events in the history of evolutionary
thought are therefore Darwin’s discovery of evolution by natural selection and the synthesis
of Darwin’s and Mendel’s theories a a synthesis variously called the modern synthesis, the
synthetic theory of evolution, and neo-Darwinism. Chapter 1 discusses the rise of evolutionary
theory historically, and introduces some of its main figures. During the twentieth century,
the sciences of evolutionary biology and genetics have developed together and some
knowledge of genetics is essential for understanding the modern theory of evolution.
Chapter 2 provides an elementary review of the main genetic mechanisms. In Chapter 3, we
move on to consider the evidence for evolution a the evidence that species have evolved
from other, ancestral species rather than having separate origins and remaining forever
fixed in form. The classic case for evolution was made in Darwin’s On the Origin of Species
and his general arguments still apply; but it is now possible to use more recent molecular
and genetic evidence to illustrate them. Chapter 4 introduces the concept of natural selection.
It considers the conditions for natural selection to operate, and the main kinds of
natural selection. One crucial condition is that the population should be variable, that is,
individuals should differ from one another; the chapter shows that variation is common in
nature. New variants originate in mutation. Chapter 2 reviews the main kinds of mutation,
and how mutation rates are measured. Chapter 4 looks at how mutations contribute to variation,
and discusses why mutation can be expected to be adaptively undirected.