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| In biology, evolution is the process whereby the frequencies
of traits within populations of organisms can change over time.
Its action over large stretches of time explains the origin of
new species and ultimately the vast diversity of the biological
world. Contemporary species are related to each other through
common descent, products of evolution and speciation over
billions of years. The phylogenetic tree at right represents
these relationships for the three major domains of life. The
understanding of evolution is based on the theory of natural
selection, which was first proposed in a joint 1858 paper by
Charles Darwin and Alfred Russel Wallace, and achieved a wider
readership in Darwin's 1859 book, On The Origin of Species .
Natural selection is the idea that individual organisms which
possess variations giving them advantageous heritable traits are
more likely to survive and repr