400 Million Years of Ferns

Ferns are all leaf, all the time—no slow preparation for the momentous flower, no seduction of the insect. At the tips of young fronds, fiddleheads unfurl, fronds lengthen, leaflets appear and widen behind the unfurling tip like the widening wake behind a boat. My store-bought Boston fern, tended for years with no expertise, bears dazzling fronds that arch up, out, and over—a fountain of green.

Ferns were among the earliest plants with roots to dig deep for water and vascular stalks and stems to transport it throughout the plant. They were the first to grow arrays of hundreds of leaves. This was almost 400 million years ago. Earlier plants had lived entirely in the water, with no need for deep roots. On land, before the ferns, the first mossy plants, lacking roots or stems, could grow no higher than a few inches. Vascular tissue—tubes that conduct fluids, minerals, and gasses—changed everything. Ferns reached the height of trees. And today vascular systems circulate the red blood through us all.

Ferns emerged late in the Devonian Period, which lasted from 419 to 359 million years ago. About 30 million years prior to the Devonian, the first of Earth’s five mass extinctions took place. The climate cooled, water froze, glaciers grew, the sea level fell, coastal and ocean habitats disappeared. As the earth warmed again, carpets of moss sprang up along lakes and streams and bony, heavy-jawed fish swam in the seas. Then ferns and other plants became the first forests.

Devonian ferns wikimedia


Toward the end of the Devonian, the second mass extinction took place. It came in three pulses. Ocean species, including the heavy-jawed fish, disappeared. But land plants, including the ferns, were mostly spared. In fact, one theory  (bbc.com/earth/story) holds that the roots of the ferns and other plants broke through rocks and released nutrients into the lakes, rivers, and oceans. The nutrients fed huge blooms of algae which later died and decayed, taking up the oxygen that had kept the fish alive. Meanwhile, again, the ferns thrived.

Ferns proliferated in part because of how they propagated. Here they were—and are—old fashioned. Instead of reproducing via miniaturized plants embodied in seeds, ferns spread through spores, single cells released from the underside of the fronds. When the spores settle on moist soil, they grow a tiny intermediate plant that will provide the fertile start for the new fern. Spore propagation seems a complicated two-step process, but the lightness of the single-celled spores let them disperse on the wind and germinate on distant, moist soil.

Some days I gawk at a plant whose distinctive family features date back 400 million years. No other plant or animal that I see every day goes back almost to the start of life on land. The ancestors invented leaves and roots but kept the old method of reproducing.  They survived four mass extinctions, as well as the flowering plants that burst on the planet 125 million years ago and dominated the plant kingdom. Ferns watched the dinosaurs come and go. Today they regale us with tales of ancient climates and their durable adaptations.


Note: Among the sources on ferns, Don Lubin’s “Introduction to Ferns” is especially readable and informative for the general reader.


Humboldt’s Vision of Nature

Humboldt portrait 1806 Friedrich Georg Weitsch (Wikipedia)

An imagining of the young Humboldt at work, in 1806, by Friedrich Georg Weitsch (Wikipedia)

Our imagination may seem to create visions out of nowhere, but it always has its sources. Some are in the psyche, some are in the world around us, many are in history, seemingly out of sight but alive in our culture. The sources for our ecological imagination, our view of nature as a global, animated, interactive and sacred whole, include the work of Alexander von Humboldt (1769-1859), a manic, prolific explorer and naturalist of the German romantic era. Humboldt’s life and work are the subject of an outstanding biography by Andrea Wulf, The Invention of Nature: Alexander von Humboldt’s New World (2015).

Humboldt’s trademark was the web of connections he drew around whatever he was observing. Nature, he insisted, could not be grasped in the slices and pieces into which other scientists chopped it but only as a whole. He looked at each specimen, whether a plant or a human institution, in its relation to global patterns of earth, weather, and human behavior. Such a perspective called for not only information but imagination and emotion as well. His works are as full of poetry as they are of data.

His seminal journey was a five-year exploration during his thirties of Latin America. Wherever he went, he compared. In the Andes, a moss reminded him of one in northern Germany. In Mexico he found trees like those in Canada. Measuring temperature and altitude as he climbed stormy volcanoes and crawled across frozen ridges in the Andes, he envisioned the plants of the world in vegetation zones consistent around the planet. He published a large diagram of a mountain with labels for plants at their respective altitudes around the world, from the mushrooms at the depths to the lichens just below the snow line. No one had ever seen a graphic that illustrated ecosystems from a global perspective like this.

Humboldt (mappingthenation.com)


Humboldt was the first to note that cutting down a forest set off a cascade of environmental problems, triggering the loss of topsoil, the rapid runoff of rainwater, the flooding of rivers, the drying up of springs, the decline of agriculture. He observed how the farming of single crops for trade, such as indigo in Peru, ruined the soil ‘like a mine,’ and impoverished the people. “He debated nature, ecological issues, imperial power and politics in relation to each other. He criticized unjust land distribution, monocultures, violence against tribal groups and indigenous work conditions” (105).

On his return from South America, Humboldt stopped by the U. S. White House to visit another scholar of agricultural economy, Thomas Jefferson. The two saw eye-to-eye on all subjects but one. Humboldt had seen enough slavery in South America to convince him that it was butchery without justification, economic or otherwise.  For Humboldt, “What is against nature is unjust, bad, and without validity,” and humans, like plants, all come from one root. “’Nature is the domain of liberty,’ Humboldt said, because nature’s balance was created by diversity” (108). Jefferson, while sympathetic, never freed all his slaves (106).

Humboldt noted similarities between the mountains of South America and Africa and argued that those continents had been joined in the past, anticipating the modern theory of plate tectonics.

In his later years in Berlin, he gave a series of free public lectures that packed halls with people from all walks of life. Traffic clogged the city on the lecture days. “He talked about poetry and astronomy but also about geology and landscape painting….He roamed from fossils to the northern lights, and from magnetism to flora, fauna, and the migration of the human race” (194). He spoke from notes layered with clippings, pieces of book pages, scribbled post-its, and illustrations.

From Cosmos, an ethnographic map of South America (eternalexploration.wordpress.com)

From Kosmos, a map of cultures and peoples in South America

He convened gatherings of scientists from across Europe to exchange information and ideas, thus establishing the modern scientific conference. Fascinated by the earth’s magnetic field, he successfully urged governments to build a network of magnetic stations across the globe, setting a new level of international scientific cooperation.

In consultation with specialists, Humboldt spent his last years writing Kosmos, a multi-volume survey of what was then known about outer space, the climate and geology of earth, the relation among plants, animals, and humans, the history of science, and the perceptions of nature by artists and poets through the ages. The huge work preceded Carl Sagan’s slimmer Cosmos by a century and a half.

In 1831, the 22-year-old Charles Darwin boarded the Beagle for his own formative voyage, bringing with him Humboldt’s seven-volume narrative of the Latin American expedition. Darwin followed Humboldt in seeing nature as a grand ecological system in constant flux and precarious balance. But while Humboldt looked for the integration of nature, Darwin looked for beginnings. On the Origin of Species appeared a few months after Humboldt’s death in 1859.

In her epilogue, Andre Wulf writes that Humboldt’s name remains unfamiliar to many because, as the last scientist to study his field so broadly, he has been eclipsed by modern specialists famous for singular discoveries and theories. (Darwin is one example.) Yet when I read today’s effusive, popular articles and internet commentary on nature and naturalistic spirituality, I hear Humboldt. The passion and breadth he brought to science set the outlines of the ecological panorama that is many people’s view of the natural world today.

Taking the Universe Personally: Neil Shubin’s “The Universe Within”

The full title is The Universe Within: The Deep History of the Human Body, (2013). Neil Shubin explores the connections between us and the history of not only the planet but the cosmos as well.

The molecules that compose our bodies arose in stellar events in the distant origin of the solar system. Changes to Earth’s atmosphere sculpted our cells and entire metabolic machinery. Pulses of mountain building, changes in orbits of the planet, and revolutions within Earth itself have had an impact on our bodies, minds, and the way we perceive the world around us. (Kindle location 197)

The linkages are fascinating. For example, huge Jupiter, formed before earth, attracted debris swirling around our early sun and influenced how the other planets formed and what they were like. “The formation of Jupiter defined the size of Earth and, in so doing, the pull of gravity on all things on its surface” (737). Had Earth been larger, its gravity would be stronger and we would be shorter and stockier. Smaller, we would be taller and thinner. A different Jupiter and we would “move, feed, and interact with our planet” differently.

Neil Shubin is Professor and Associate Dean of Organismal Biology and Anatomy,at the University of Chicago. (interactive.wttw.com)

Neil Shubin is Professor and Associate Dean of Organismal Biology and Anatomy at the University of Chicago.

Different readers will be impressed by different connections. I found the most significance in events that impacted the course of biological evolution. One example is the shift from single-celled creatures exclusively during the first two billion years of life on earth to the beginning of bodies—plant and then animal. Early life was small. It was more affected by the interaction of molecules than by  gravity. Single cells transport oxygen, food and waste by diffusion through the cell. But bodies require organs and systems for transport. Why did life become bigger? Oxygen, a chemical energizer, became more available after a decline in the number of undersea volcanoes that had been spewing gases that consumed oxygen. “Life changes Earth, Earth changes life, and those of us walking the planet today carry the consequences within”(1344).

And I got goose bumps when Shubin described the cooling of earth that favored the mutation in mammals for seeing colors which in turn enabled them to find more nutritious fruit. The tracing of a particular human ability back to a huge geological shift was, to me, thrilling. But I had no goose bumps for other linkages that seemed more general and less personal—the impact of the moon’s birth, for example, on the length of our days, seasons, and circadian rhythms. For other readers, though, the goose bumps may come the other way around. What arouses our awe depends on the questions we ask about life, what we feel driven to understand, and what scares us.

Shubin refers to religion only once. He cites William James’ observation that religious experience emanates from our

‘feeling at home in the universe.’ With bodies composed of particles derived from the birth of stellar bodies and containing organs shaped by the workings of planets, eroding rock, and the action of the seas, it is hard not to see home everywhere. (2529)

Some readers may find it difficult to see home everywhere in the way that Shubin does. But his synthesis helps make separate descriptions of biology or the planet or the cosmos less adequate as grand accounts of that home.