Get Ready for an "Abominable Mystery" to Emerge on the Prairies!

In 1879, Charles Darwin wrote to his good friend and fellow botanist Joseph D Hooker that "the rapid development as far as we can judge of all the higher plants within geologic times is an abominable mystery". In this famous quote, Darwin was referring to the flowering plants or angiosperms and was perplexed and mystified about their rapid appearance in the fossil record which seemed to upset his theory of evolution occurring slowly and incrementally over long periods of time. The angiosperms seemed to appear suddenly in the mid Cretaceous period, about 100-125 million years ago, without clear intermediate ancestors, then quickly diversified in an explosion of color, shape, and form conquering the world in a geologic blink of an eye. Darwin believed strongly in natura non facit saltum or "Nature does not take a leap". But the angiosperms seemed to take a big leap, much to Darwin's chagrin, providing his critics with arguments against his theory. Three years later, Darwin died, still haunted by this mystery.

Today, angiosperms are the most diverse group of plants, dominating the landscape and comprising 80-90% of terrestrial plants, including forbs, grasses, most deciduous trees, shrubs, vines, and even most aquatic plants. Their sudden evolutionary success is now attributed to many factors, but high on the list is their coevolution with certain insects. Before angiosperms, the primary relationship between plants and insects was antagonistic, with insects posing a threat to plants, much like the modern emerald ash borer or the spongy moth. However, with the emergence of angiosperms, this relationship transformed into mutualism for some insects, benefiting both plants through pollination and insects through food. And the race was on among the flowers to attract insects that were most skilled at performing this task leading to a splash of vibrant colors (including in the ultraviolet part of the spectrum which insects can see but humans cannot), forms, scents, and above all nectar. At the same time, the pollinating insects evolved alongside flowering plants leading to a wide variety of bees, wasps, butterflies, and flies that took on specialized roles in pollinating select plants.

Evolution is now understood to occur both in the slow and steady manner championed by Darwin called gradualism and in bursts after periods of stasis called punctuated equilibrium. Kind of like the tortoise and the hare- sometimes the slow, grinding, methodical tortoise wins the race, but other times that pesky rabbit prevails. Angiosperms came on the scene in an initial big bang to win the evolutionary race in the manner of the rabbit, pushing gymnosperms aside (most of which are conifers) to become the dominant terrestrial plant. This burst in evolution occurred in a bang, but was not a singular event. After the big bang, many mini-bursts occurred in the coevolution of these plants and their insect partners leading to the wide variety of flowering plants we see settled onto the landscape today.

Nature is full of surprises that astonish even the best minds in science. These unexpected discoveries that challenge existing paradigms often lead to great leaps in a discipline. The mysterious emergence of flowers reminds me of a well-known quote from physics by Isador Isaac Rabi, the Nobel Prize winning American physicist who was instrumental in bringing the forefront of physics to the United States in the 1930's and 1940's. When the muon, a subatomic particle and cousin to the electron, was discovered in 1936, it shook the world of physics, but paved the way for the new field of particle physics. When Rabi learned about the discovery of this new particle, he famously quipped, "Who ordered that?" His comment went on to become a standard, frequently quoted remark to describe surprising, unexpected phenomena that do not fit into the current theoretical framework. Like the big bang of flowers in Darwin's time.

So, when you see the prairies bursting forth in their full glory of flowers as they emerge from their winter slumber, think of Darwin wrestling with his "abominable mystery" in his final moments and perhaps thinking, "Who ordered that?"