.......the theory of evolution is in crisis. But this is a positive development, because it reflects the non-linear progress of scientific knowledge, characterized by what Thomas Kuhn described in his influential book The Structure of Scientific Revolutions as “paradigm shifts.”
For the last 70 years, the dominant paradigm in evolutionary science has been the so-called “new synthesis.” Widely publicized in recent years by Oxford evolutionary biologist Richard Dawkins, the new synthesis unites Darwin’s theory of natural selection with Mendelian genetics, which explains heredity.
The current crisis in evolutionary science does not imply complete rejection of this paradigm. Rather, it entails a major, progressive reorganization of existing knowledge, without undermining the fundamental tenets of evolutionary theory: organisms alive today developed from significantly different organisms in the distant past; dissimilar organisms may share common ancestors; and natural selection has played a crucial role in this process.
Other assumptions, however, are under threat. For example, in the traditional “tree of life” representation of evolution, the branches always move apart, never merging, implying that species’ ancestry follows a linear path, and that all evolutionary changes along this path occur within the lineage being traced. But examination of genomes – particularly microbes – has shown that genes moving between distantly related organisms are an important catalyst of evolutionary change.