Did Plants Evolve?

Plants and trees

Have you ever seen a fossil plant series in a museum display or textbook on evolution?

Alexander Williams

When I studied botany at university in the 1960s they taught us evolution and paleobotany (the study of plant fossils) but not a single fossil series was ever presented as evidence that plant evolution actually did occur. So, when I saw a new book recently entitled The Diversity and Evolution of Plants, dated 1995 and published by the CRC Press, a reputable publisher of top quality scientific manuals and textbooks, I was keen to see what new evidence had arisen during the last 30 years of research. The author, Dr Lorentz Pearson, appeared to be well qualified, being a Professor of Botany with a string of credits to his name.

In the Preface, Professor Pearson asserts that evolution is a fact attested to by the fossil record. The Introduction is entirely devoted to a narrative description of that evolutionary history.

The main body of the book consists of 18 chapters that deal with the whole plant kingdom at the level of its 29 classes. Each chapter contains a diagram of the ancestor-descendant relationships between each class and its near neighbours and between the subdivisions within each class; such diagrams are called ‘phylogenetic trees’. On my first run through the book I combined the information in the phylogenetic trees to make a single tree so that I could see Professor Pearson’s complete evolutionary history in visual form (see Figure). I have avoided, where possible, the rather long and obscure technical names for the classes and have just identified each class with the common name of a representative member.

The figure shows that, according to Pearson, every class evolved from another class, with the bacteria being the original ancestor of all the others. There was only one questionable connection; Pearson was uncertain whether the brown seaweeds had evolved directly from the dinoflagellates, or whether they had arisen indirectly from the dinoflagellates via the yellow-green algae. According to Pearson’s diagram the history of plant evolution is almost complete.

Each chapter is divided up into consistent sub-sections, one of which is headed ‘Phylogeny and Classification’. Phylogeny means ‘evolutionary history’. So I then began to read what Professor Pearson had to say about the fossil evidence from which he derived his evolutionary histories. In the face of the confident Preface, Introduction and phylogenetic tree diagrams, what I found was rather surprising.

In all 18 chapters, not a single fossil series was quoted or illustrated to support the phylogenetic trees! Many groups have excellent fossil records, but not once does he indicate that there is unequivocal evidence of transition from one to another, as evolution requires…


image credit: Sebastian Unrau