Flowers may be more ancient than dinosaurs – but scientists can’t agree on when they evolved

• Including more than 350,000 known species, they dominate the ecological system, shape food webs and play a vital role in oxygen production.
• Plus, many of them are valuable commercial crops – think of roses, grains and tomatoes.

• A step change in research is shaking up the way scientists think about plants: they are far more complex and more like us than you might imagine.
• But not all scientists agree it is an angiosperm, due to the different definitions of flower organs.
• This is the largest known amber-preserved fossil flower, measuring about 3cm across and about three times as large as most floral fossils, showing beautiful details of this ancient flower.

Jurassic or Cretaceous?

• The timing of flowers’ evolution is still a matter of debate between scientists, but most scientists are in one of two camps: Jurassic or Cretaceous.
• Analyses using molecular data (DNA or protein sequences) suggest flowers could be much older than the fossil record shows – a Jurassic (145 million years ago) or even Triassic origin (201 million years ago).

Deciphering the past by molecular data

• One technique scientists use to determine the timing of evolutionary events is the “molecular clock”.
• This concept originated from the understanding that genetic mutations tend to accumulate at a constant rate across both time and species.
• To construct a molecular clock, researchers analyse gene segments that have been conserved throughout a species’ evolution.

Piecing the puzzle together

• Scientists examine fossil plants and observe the gradual changes in structures such as leaves, flowers and seeds over time.
• Comparing their anatomy allows researchers to identify similarities and differences between extinct and still-living species, or species in different clades.
• Biological traits which appear similar may be a result of convergent evolution, indicating changes in characteristics for environmental adaptation, rather than genetic similarity.

Mathematical approach can also help

• There is also a mathematical approach to estimating the age of angiosperms – for instance, using the Bayesian Brownian Bridge (BBB) method.
• This statistical model is a scientific formula that uses the distribution of fossils through time to estimate the age of a group.
• By using the BBB method, an international research team found that the origin of angiosperms supports a pre-Cretaceous hypothesis.

Ruolin Wu does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.