In Search of the First Flower

By Dr. David Galbraith, Head of Science, Royal Botanical Gardens.

Flowers are everywhere in our world today. The majestic Magnolias, Lilacs, and Roses are all flowering plants, or Angiosperms. So are many plants we eat, and even humble little tufts of grass that live in city pavement. They are beautiful, they enrich our culture, and are of great economic importance. It’s hard to imagine our world before plants had flowers.

Land plants show up in the fossil record over 400 million years ago, in the Silurian Period. A variety of fossil plants with true flowers appear much later, in the Cretaceous Period. This period stretches from about 65 million years ago (MYA) back to about 145 million years ago and by the end of the Cretaceous most of the major flowering plant families we know today were in existence.

One hundred and fifty years ago Charles Darwin puzzled over the sudden appearance of fossil flowers in the Cretaceous. When had the earliest flowering plants evolved? Researchers from Switzerland, Sweden, China, and the UK may have an answer. They applied statistical methods to try to narrow down the age of Angiosperms in a paper published this year (1). They mapped the appearance of early families of flowering plants during the Cretaceous and more recent Cenozoic Era. Then they ran a mathematical model backward in time, into the earlier Jurassic Period. They found that a large number of flowering plant families may have had their origins in the Jurassic, between 145 MYA and 200 MYA. Some may have originated in the even earlier Triassic Period. Other researchers studying DNA sequences have made the same suggestion. Flowering plants likely diversified in the Jurassic.

Two years ago, researchers in China actually found fossil flowers dating from the Jurassic: Nanjinganthus dendrostyla, a flower from more than 174 million years ago (2). These ancient blooms are strong evidence that flowers have been around a very long time.Insects, the great ecological partners of flowers, also had an early start in the fossil record. The earliest known insect fossil is 400 million years old, from chert deposits in Scotland (3). In the Triassic Period, before the Jurassic, insects increased in their diversity so it’s tempting to think that insects in the late Triassic or early Jurassic were a factor in the rise of flowering plants. A study of 29 living “basal” or early-appearing Angiosperm families indicated that that may have been the case (4). Floral structures that suggest insect pollination appear in early fossils of 86% of these families.

The ancient association between flowers and pollinating insects is important to us today. It has given us all the benefits of flowering plants, from their beauty. to much of our food. It may also have been a significant part of the origin of flowers themselves. We have insects to thank for the flowers we love so much today.

Resources

1. Silvestro, D., Bacon, C.D., Ding, W. et al. 2021. Fossil data support a pre-Cretaceous origin of flowering plants. Nature: Ecology & Evolution https://doi.org/10.1038/s41559-020-01387-8
2. Chinese Academy of Sciences. 2018. Flowers originated 50 million years earlier than previously thought. EurekAlert! Science News. https://www.eurekalert.org/pub_releases/2018-12/caos-fo5121818.php
3. Engel, M. S., and Grimaldi D. A. 2004. New light shed on the oldest insect. Nature. 427 (6975): 627–630. doi:10.1038/nature02291
4. Shusheng Hu, S., Dilcher, D. L., Jarzen, D. M., and Taylor, D. W. 2008. Early steps of angiosperm–pollinator coevolution. PNAS January 8, 2008 105 (1) 240-245; https://doi.org/10.1073/pnas.0707989105