The Darwin Awards Next Evolution: Chlorinating the Gene Pool (12 page)

A
few hundred years ago a new fad swept through the privileged ranks of European aristocracy. It was a substance refined from an enigmatic plant brought back from the New World. Hailed as a godsend by some, more recent experience has shown that long-term consumption can lead to erratic behavior, serious weight fluctuations, and systemic organ failure. Even first-time users can, although rarely, fall victim to fatal cardiopulmonary shock. But it is not all bad. I must confess, on my first date with my future wife, she and I both indulged. The mysterious extract soon worked its neurotransmitter magic. We gazed enraptured into each other’s now-blazing eyes, and we fell madly in love.

If you travel back to the opening days of the Cretaceous Period, you are well advised to watch your step. Saurian monsters abound. Hungry eyes watch from ambush. Hordes of tiny ratlike mammals slumber by day in fur-lined burrows, emerging to feed at dusk. Aside from running afoul of a carnivorous titan, you must be careful of the little critters as well. Tread on the wrong lair and you might crush dear old Great-to-the-Zillionth Grandpa in his sleep, wiping out the entire human race and giving rise to the dreaded Grandfather Paradox. With so much to worry about, it is easy to miss the most important new organism to arise in ages, standing low in the tangled bank at the steamy water’s edge.

It is the world’s first blossom.

The little pockets of flowers were unobtrusive in a world ruled by colossal carnivorous monsters. But the small flowering shoots had already struck a partnership with the most successful animal taxon on earth, the insects, and would soon team up with the rest of the animal kingdom. In its own vegetable way, the flower was poised to take over the world.

Botanists classify so-called higher plants, meaning those with roots, veins, and leafy structures, into two main groups: angiosperms and gymnosperms. Flowering plants are angiosperms. Conifers, which produce the familiar pinecone, are an example of gymnosperms. Both produce seeds. However, the seeds of angiosperms are surrounded by a fleshy vessel, or an
angio
in Latin, forming an often tasty wrapper. The seeds of gymnosperms lack an equivalent structure and thus are “naked,” or in Latin,
gymno.

The origin of flowering plants is a hotly debated topic. Some say there is indirect evidence for a possible ancestor over two hundred million years ago. But the oldest unambiguous fossil evidence for a flowering plant is found in China and dates to about 125 million years ago. It was named
Archaefructus sinensis
, “ancient Chinese fruit.”

Regardless of when they first evolved, plants had hit on an ingenious survival strategy. Rather than playing an inadvertent role in the mandibles, jaws, and gullets of ancient insects, they created a sort of organic peace offering, free for the taking. Pollen and sweet nectar was given as payoff for cross-fertilizing the new angiosperms. The flower blossom itself likely evolved as a visual transponder beacon. The blooms even developed secret patterns invisible to the eyes of vertebrates, flashing rings and other enticing patterns in ultraviolet wavelengths to wave in their insect couriers.

By the Middle Cretaceous, some ninety million years ago, birds were probably in on the act, recruited by flowers to carry plant pollen in their feathers and seeds in their stomachs. They flew across the young and growing Atlantic Ocean to every island and continent. Flowers of all kinds evolved, each in elegant resonance to the needs and desires of their local animal partners. By the Late Cretaceous, twenty million years later, the luxuriant emerald-green world of the dinosaurs had been adorned with bright blossoms and sweet scents.

After dinosaurs disappeared sixty-five million years ago, plant-munching mammals rose to prominence, and flowering plants came up with their next smash hits: fruits and grasses. Citrus fruits in particular, of the group
Rutaceae
, are a favorite of tree-dwelling animals. The animals eat the fruity prize; the seeds are safely transported all over the jungle and then deposited in a steaming pile of rich animal fertilizer.
Liliopsida,
an angiosperm better known as grass, appears widely in the fossil record in the Eocene. By thirty million years ago grasses dominated the flat savanna and provided food for the largest mammals ever to walk the earth.

Over the next twenty-five million years a few of these hardy flowering grasses evolved into the forerunners of modern cereal grains: wheat, corn, and rice. Those three grains account for over half the calories in the modern human diet. A whopping five trillion calories of cereal are consumed each day, and two trillion more in the form of tubers, vegetables and vegetable oil, fruits, syrups, and other sugars made from flowering plants. Added to that, every pound of meat we eat conservatively represents thousands of calories of commercial cereals and wild grasses.

The Plant Kingdom could not have supported the kinds and numbers of animals it does today before the advent of flowering plants. And even with the sweet fruits and toothsome grains they offer, artificial selection was required, operating over millennia on hundreds of angiosperm species, so that humans can harvest the amount of food we currently eat.

Quite literally, human beings are flower-powered.

Teosinte (top) began as a single stalk of kernels, each enclosed in its own individual husk. Over time artificial selection produced strains with large kernels and softer husks, until we can recognize the first corncobs (center). Modern corn (bottom) is a mutant version so freakishly large it cannot survive or reproduce without human cultivation and care. Illustration by Karen Wehrstein.

How is all this ancient flowery history known or suspected? Some is educated guesswork. But much of it falls under the purview of paleobotany and palynology, the study of ancient pollen. Most small plants don’t lend themselves to fossilization. But plant pollen is tough and fossilizes well. Particular groups of plants can often be distinguished by their pollen. Thanks to the painstaking dedication of thousands of botanists over the years, we have developed a robust database of ancient pollens, tracing the evolutionary radiation of angiosperms onto the global stage.

Of course, the flowering plants could never fully trust their new animal partners. Given half a chance the animals would gobble down the whole plant: fruit, nut, flower, leaf, stem, and root. Evolution quickly produced critters that did exactly that. The plants responded by incorporating substances that give the offending critter a stomachache or worse if it eats the wrong part at the wrong time.

Many of our early medicines and modern drugs come from such defenses. The plant chemicals are bioactive by definition, because they are meant to affect the biology of the animal that eats them. Quinine from tree bark, caffeine from the coffee bean, narcotic painkillers from the opium poppy, and aspirin from the willow tree are substances that don’t pose quite as much danger to us as they do to insects and their ilk. Unlike the bugs’, our bodies come complete with sophisticated, factory-installed detoxification systems. In fact, for humans, the effects of some of those natural insecticides are downright addictive.

Which brings us back to that first date with my future wife and the highly habit-forming, brain-altering substance we ingested at the dawn of the new millennium. The source was an enigmatic flowering plant found in the New World. The substance it produces is sublime. Yet we broke no drug laws. It was first used in a crude form thousands of years ago by Native Americans in what is now called Central America. The Aztecs called it
xo-co-latl
. But we know it today as chocolate.

Cretaceous dating:

Ji, Q., H. Li, L. M. Bowe, Y. Liu, and D. W. Taylor, 2004. Early Cretaceous
Archaefructus eoflora
sp. nov. with bisexual flowers from Beipiao, Western Liaoning, China. PDF (3.11 MiB).
Acta Geologica Sinica.
78(4): 883–896.