In Why Is a Fly Not a Horse?, Giuseppe Sermonti explains why evolution resembles a “paradigm” more than it does an explanation. Scientists assume that the theory and its implications (such as universal common descent) are true, but no one can ever explain the details of precisely why it is. According to Sermonti, naturalistic theories of biological origins are science-stoppers.
Sermonti explains that biology has advanced greatly when naturalistic theories of biological origins have been disproved. For example, in 1688 Francesco Redi performed an experiment which refuted the notion that flies come from rotting meat—Redi discovered that flies actually come from worms that hatch from eggs laid in rotting biological matter which subsequently develop into flies. The recognition that flies come from eggs rather than meat fostered our early understanding of biological development, but one theory of spontaneous generation had to die before the advance was made.
Sermonti recounts that the field became stalled when the early evolutionist Comte de Buffon imagined that everything from fleas to the hippopotamus emerged from the primordial slime. Providing an Italian perspective on the history of biology, Sermonti explains that an Italian naturalist named Spallanzani refused to just accept spontaneous generation as the easy answer, and through a series of carefully observed experiments, came to the conclusion that “omne vivium ex ovo” (all life comes from eggs). Spontaneous generation was finally disproved by Pasteur’s experiments nearly a century later. This was a fact lamented by Darwin, who claimed that Pasteur “denied spontaneous generation.” Despite Pasteur’s “denial,” biology progressed.
Sermonti turns to the primary question of his book: Why is a fly not a horse? According to Sermonti, developmental genes are widely similar across various species. Providing a tour of genetic development, Sermonti finds that genes alone may not be enough to account for differences among the species, something that would pose a profound challenge to Darwin’s theory.
Giuseppe Sermonti is a retired professor of genetics at the University of Perugia and the chief editor of Rivista di Biologia/Biology Forum, one of the oldest still-published biology journals in the world. He is the author of seven books, including Genetics of Antibiotic-producing Microorganisms, Dopo Darwin, Fiabe dei fiori, and Il mito della grande madre.