Flowering Plant Explosion / Angiosperm Radiation

Not to be outdone by the animals of the Cambrian explosion, plants have their own example of sudden appearance. And what an example it is! Darwin called the origin of flowering plants an “abominable mystery” and scientists in the field still admit that nothing has changed in the 150+ years since Darwin wrote Origin of Species.

Flowering plants are an amazing group. They are seed plants like the gymnosperms [means naked seed] but unlike them, flowering plants protect their seed in a fruit. Angiosperm means ‘encased seed’. Unlike the gymnosperms (conifers, cycads and Ginkgo ) which boast only approximately 1000 species, angiosperms/flowering plants are represented by about 370,000 species. [One Thousand Plant Transcriptomes Initiative. 2019. Nature 574: 679-685. See p. 682-3]. Indeed, the Angiosperms constitute about 80% of all the terrestrial green plants and their diversity is phenomenal.

So, what are the special characteristics of the flowering plants? There are major innovations all of which would require considerable new information and controls. Obviously, the flower is special. It encases the developing seed (initially an ovule) inside a carpel (stigma, style and ovary) which develops into the fruit. Moreover, the angiosperms exhibit multiple other key innovations including double fertilization and vessel elements for conducting water in the xylem.  [Nature p. 683].

Double fertilization is a key feature of the Angiosperms. When the haploid egg is fertilized with a nucleus from the pollen grain, a second nucleus, also from the pollen grain, unites with two polar cells [products from the same meiotic division in the ovule]. The fertilized egg develops into the embryo in the seed and the results of the second fertilization yield a triploid or polyploid tissue which develops into the endosperm in the seed. We cannot overemphasize the importance of the endosperm. It stores up and provides nutrients for the germinating seedling, but it also literally feeds many populations which cannot manufacture their own food. The grains from the grasses (like wheat and rye, oats, rice and corn) and so many other nutritional seeds all come from the endosperm. Then of course there are nutritious fruits as well.

When we think of the rest of the land plants other than the angiosperms, their potential to feed animal populations is poor indeed. These plants tend to be tough. It is the Angiosperms that keep the trophic pyramid on land going. But the interesting thing is that Angiosperms appear in the fossil record only in Lower Cretaceous rocks and they then really show amazing diversity higher up in the Cretaceous rocks. In an evolutionary scenario, this would be close to the time of extinction of the dinosaurs. Scientists want to know why or if the flowering plants took so long to appear and how they managed to show such rapid radiation. This sudden appearance, with no ancestors evident, and with lots of sophisticated innovations, is what constitutes the Angiosperm Radiation!

Scientists are still far from answering the mysteries of the angiosperm radiation. Still no angiosperm fossils have been found in rocks lower than Cretaceous rocks. Thus, a botany text book author declared in 1972 “In spite of advances in our knowledge of comparative floral morphology and of the fossil record, and in spite of the publication of many pages of speculation on this subject, Darwin’s words still eloquently summarize the current state of our knowledge.” [H. C. Bold. Morphology of Plants. Harper and Row. pp. 668. See p. 601]. Bell, Soltis and Soltis in 2005 similarly declared: “A minimum age estimate is provided by a variety of fossils from the Barremian-Aptian boundary (125 million years ago; mya) in the Early Cretaceous.” [The Age of the Angiosperms: A Molecular Timescale without a Clock. Evolution. pp. 1245-1258. See p. 1245] and Sawal in 2021 also admitted: “The oldest angiosperm fossils so far found are 135 million years old, and many researchers believe this is when the group originated.” [New Scientist January 28, 2021 p. 1]

Obviously, scientists are far from satisfied with this answer of the late appearance and extraordinarily rapid diversification of the flowering plants. As with the Cambrian explosion, they have turned to molecular clock models to suggest that the angiosperms appeared much earlier. Bell, Soltis and Soltis discuss early attempts to apply molecular clock estimates to the issue. They point out the “grossly inconsistent” and “widely divergent” age estimates that result either by applying a “strict molecular clock” or “relaxed assumptions” of varied rates of change among the lineages. [pp. 1245-1246]

A molecular clock study was published in 2019 by scientists from China, Australia, USA and Scotland. They claimed it was the most comprehensive family tree to date of the flowering plants and they calibrated their study against some plant fossils. The key “finding” (conclusion) of their paper was that the point of origin of all modern flowering plants came from the Triassic Period ~209 mya.  But there are problems. “This leaves an enormous period of time, roughly 70 million years and spanning the entirety of the Jurassic Period, during which angiosperms were present but left no trace.” [Alex Davey. May 8, 2019. Royal Botanical Gardon of Edinburgh Personal and Project Stories p. 4] The authors of the study called this interval which lacks evidence of the presence of angiosperms “the mysterious Jurassic Gap.” [based on Li, H.-T. et al.2019. Origin of angiosperms and the puzzle of the Jurassic gap. Nature Plants. https://doi.org/10.1038/s41477-019-0421-0

The new study in 2021 relied on comparisons of modern plants with fossil specimens. The authors wanted to develop a model that only relied on fossils and which specifically excluded molecular data. They attempted to draw a line between modern diversity and the time when the first ancestors of flowering plant families appeared. Their analysis provided “strong evidence that the oldest angiosperm may have appeared perhaps as early as 250 million years ago, during the very end of the Permian period – much earlier than the oldest known angiosperm fossil.” [emphasis mine. Ibrahim Sawal. January 28, 2021. Flowering plants may be 100 million years older than we thought. New Scientist  p. 2] This gap is even longer than the mysterious “Jurassic gap”. This conclusion however met the expectations of the scientific team. They assumed that the ancestors of the flowering plants would have had to appear much earlier than the earliest fossils.  Commenting on the situation, Professor Philip Donoghue at the University of Bristol declared “Rather than a mythical artifact of genome-based analyses, Jurassic angiosperms are an expectation of our interpretation of the fossil record.” [emphasis mine. Sci News Feb. 9, 2021 p. 3] [based on D. Silvestro et al.2021. Fossil data support a pre-Cretaceous origin of flowering plants. Nat. Ecol. Evol. Published online January 28.  https://doi.org/10.1038/s41559-020-01387-8  ]

These models are exercises, based on evolutionary expectations, in explaining away the observations from the rocks. Dr. Christine Bacon, a molecular biologist from Gothenburg Global Biodiversity Centre, insists that “the fossil record has to be interpreted.”  Computer models are a necessary tool in this study. Thus, she declares: “A literal reading of the fossil record cannot be used to estimate realistically the time of origin of a group. Instead, we had to develop new mathematical models and use computer simulations to solve this problem in a robust way.” [Sci News p. 3] Obviously evolutionary assumptions, not actual observations, are driving the evolutionary story.

Of course, creation scientists too have to deal with the sudden appearance of flowering plant fossils high up in the rock record. Two things to keep in mind are that all these organisms were created during the creation week, so they were contemporaneous with other organisms buried in the rocks. Like the rest of those pre-flood communities, they were all overtaken by flood waters. The order in which creatures were buried and preserved depended on their elevation on land or in the sea, and the rate of sinking of the materials washed off the land.   The key thing to remember is that evolution could not possibly accomplish this amazing diversification in a few million years. Thus, evolutionists need to develop explanations that call for a long slow period of evolution. We declare alternatively that the flowering plants are amazingly designed for the benefit of mankind and the animal populations. The sudden appearance demonstrates that they did not evolve but were instead created in their amazing diversity.