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First Paragraph: It has been over 30 years since the suggestion that horizontal gene
transfer (HGT) may have been a factor in the evolution of life entered
the literature. Initially these speculations were based on discoveries
made in medical microbiology, namely, that genes for resistance to
antibiotics were found to move from one bacterial pathogen to another.
This discovery was so unexpected and contrary to accepted genetic
principles that though it was announced in Japan in 1959 [1,2], it was
not generally recognized in the West for another decade. Speculations
that HGT may have been a bigger factor in the evolution of life was
inviting because it offered broad explanations for a variety of biologi-
cal phenomena that have interested and puzzled biologists for over the
last century and a half, These were problems that had been raised by
botanists who have puzzled over the evolution of green plants 131 as
well as by paleontologists who recorded macroevolutionary trends [4]
in the fossil record that were often difficult to reconcile with the New
Synthesis that merged Darwin's thinking with Mendelian genetics.
However, outside of the field of bacteriology this exercise did not really
attract that much attention until the late 1990s, at which time there was
a major influx of data indicating that HGT had been very pervasive in
early life. Namely, complete genome sequences began to appear.
Simple examination of these sequences showed beyond any doubt that
horizontal gene transfer was indeed a major factor in the evolution of
modern bacterial, archaeal, and eukaryotic genomes.
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