Darwin called it “an abominable mystery.” He simply could not explain why flowers had appeared so suddenly in the fossil record, as if they had sprung from nowhere to dominate the planet. Well, perhaps he was right to be puzzled: the origin of flowers is even older than he imagined.
Four pollen grains measuring just 0,02 millimetres in size, found in coastal sediments off Portugal, They just backdated the origin of flowers to 123 million years ago. Two million years earlier than we thought. Nature, evidently, always has some surprises in store for those who are too sure of their certainties.
When it all began in the Cretaceous
The story begins in the laboratories of the University of Hannover and the University of Bonn, where researchers analyzed marine sediments from the Portuguese Lusitanian Basin. Julia Gravendyck and his team were searching for traces of ancient life when they stumbled upon something that would make any paleobotanist jump out of their seat: 123-million-year-old fossil pollen.
Imagine the scene: thousands of years ago, these grains fell into a river, were swept downstream, and finally reached the sea, where they settled in the sediments. There they remained, perfectly preserved, like little time capsules that tell us about the first origin of flowers on earth.
Professor Ulrich Heimhofer of Leibniz University in Hannover explains that “the emergence of flowering plants has considerably altered biological diversity.” But exactly where and when this development began has been the very enigma that Darwin already called an “abominable mystery.”
The peculiarity of these grains lies not only in their age, but in their structure. Each one has three small grooves on the external wall, a distinctive feature of tricolpate pollen, used by over 70% of current angiosperms. It is like finding the fingerprint of the first flowering plants ever to exist.
The technology that reveals the secrets of the origin of flowers
To find these microscopic grains, researchers had to use cutting-edge technology. Like most mammals, these pollens fluoresce under the right light. When a confocal laser scanning microscope shone on some sediment, four tiny grains lit up like little stars in samples collected 27 kilometers apart.
But how can you be sure of the age? Here comes into play a particularly precise dating technique: the analysis of strontium isotopes of shells buried in the same layer. Calcium carbonate shells carry with them a chemical record of the seawater in which they formed. By comparing their isotopic levels with global reference data, Scientists have managed to date the sediment with high precision.
Before this discovery, the oldest pollen grain had been found on the Isle of Wight in 1990 and estimated to be 120,4 million years old. In addition to being even smaller than the Portuguese grains, that grain looked very similar to the new discoveries. It's as if we had found relatives of a very, very old family.
The Origin of Flowers and the Domination of the Planet
Angiosperms today represent about 80% of all known living green plants.. They are so close to universal that they sometimes seem synonymous with plants to non-botanists. Conifers maintain their dominance in the forests of the far north and provide the tallest trees on the planet, but otherwise non-flowering plants are represented by the humble mosses and ferns that literally survive in the shadow of flowering plants.
Yet for nearly three-quarters of the time since plants first became established on land, there were no flowering plants. The development of pollen, and with it a vastly expanded range of options for conquering new territory, changed all that. But even a major innovation like this takes time to spread, so it was millions of years before angiosperms were widespread enough to be evident in the fossil record.
As we have highlighted when analyzing the impact of climate change, pollen is an incredibly strong and versatile structure. Its wall is made up of sporopollenin, an extremely strong and stable polymer that protects the granules during their journey from the stamens to the pistil.
Eudicots and the Origin of Flowers
The plants responsible for these ancient grains were eudicots, angiosperms with two seed leaves when they germinate. This detail is far from trivial: eudicots include many modern plants such as roses, sunflowers, and oaks. Until now, it was widely believed that this important group of flowering plants emerged about 121 million years ago. But this new discovery pushes that timeline back two million years.
The discovery in Portugal was in the middle latitudes during the early Cretaceous, just like today. This calls into question the hypothesis that angiosperms first appeared in the tropics, although the authors say this “remains plausible.” It is possible that the origin of flowers occurred simultaneously in different regions of the world, or that the first flowers spread more rapidly than we imagined.
The mystery deepens when we consider that we still don’t know much about what kind of plant sparked this world-changing innovation, though they certainly started small. Reconstruction of the first ancestral flower suggests that it was bisexual, with female and male parts, and with multiple petals arranged in concentric circles.
The Future of Flower Origin Research
Whether this was the birthplace of the angiosperms, or whether they arose earlier somewhere else, cannot yet be determined. But the discovery shows that the first flowers needed some updating to achieve their eventual dominance.
The reason Darwin found the mystery so abominable is that flowers seemed to go “from zero to one hundred” in far too short a time in the fossil record. However, those few layers of rock that separated the absence of flowers from their dominance represented millions of years, something Darwin could not have known at the time.
The evolution of angiosperms was characterized by a transformation in the capillarity of the leaves that improved their photosynthetic efficiency. Their rapid diversification led Darwin to hypothesize that they had evolved on an island or a continent yet to be discovered. A theory that, in light of the new discoveries, may not be so far from reality.
The Modern Implications of the Origin of Flowers
Today, angiosperms dominate the Earth's surface and vegetation in more environments than any other plant group. As a result, They are the most important final source of food for birds and mammals, including humans. Furthermore, flowering plants are the most economically important group of green plants, serving as a source of pharmaceuticals, fiber products, timber, and ornamental plants.
The ability of angiosperms to establish synergies with insects and other animals, in the processes of pollination and dissemination, is one of the reasons for their evolutionary success. Plants and animals have been protagonists of a phenomenon of coevolution that has allowed them to reach the current levels of high biodiversity.
It is interesting to note how pollen continues to be the protagonist of modern innovation.: Singapore researchers they have developed a paper made from sunflower pollen that can be erased and reused multiple times, demonstrating how this ancient biological structure continues to inspire contemporary technological solutions.
The Legacy of a Microscopic Discovery
The research, published on Proceedings of the National Academy of Sciences, is a perfect example of how science often proceeds through seemingly tiny discoveries that reveal enormous truths. Four pollen grains, each smaller than the width of a human hair, have rewritten the timeline of the origin of flowers on Earth.
Professor Heimhofer concludes that the emergence of flowering plants has considerably altered biological diversity. But now we know that this process began at least 2 million years earlier than we thought. It is a lesson in humility for all of us: nature always has some hidden surprises, even in the smallest details.
Whenever you look at a flower, remember that you are looking at the result of an evolutionary innovation that began 123 million years ago. An innovation so successful that today it is difficult to imagine the world without it. And it all started with pollen grains so small they are almost invisible, but powerful enough to change the face of our planet forever.
Next time you sneeze at pollen, remember: you are reacting to one of nature’s oldest and most successful inventions. Darwin would certainly have appreciated the irony.
