Planet of the Bugs: Evolution and the Rise of Insects (30 page)

The Cretaceous world was a beautiful place filled with flower meadows, butterflies, bees, duck-billed dinosaurs, and birds. One day that beauty was disturbed by a violent asteroid. We don’t know for sure if the big dinosaurs died on that day, or lingered on for years or centuries, but we can be certain that somewhere in North America, roughly sixty-six million years ago, the very last
Tyrannosaurus
did die. Exhaling a final breath of air from its voluminous lungs, the King of the Thunder Lizards was no more. Some nearby beetles and flies likely fed on its heroic fallen body. For me, that death, more than any asteroid impact, best symbolizes the end of the Mesozoic era.

10

Cenozoic Reflections

1:05
AM
. Sounds of Quito: the constant drone of auto engines, horns tooting, people talking, shouting, whistling, yelling, engines revving, sirens toot and wail, planes overhead, the constant rhythm of human street noise above the taxis, the accelerating buzz of a motorcycle, police whistles—a car alarm—pulsing. . . .

NOTES FROM MY FIELD JOURNAL

      
Quito Reverie

      
The pulsating stream,

      
Of paired crimson tail-lights,

      
On taxi cabs, flows, one-way,

      
Diagonally up the Avenida,

      
Like red blood cells, in an artery.

      
The conduit—thick with cars at midnight,

      
Nearly bumper on bumper,

      
Now flows loosely at half-past one.

      
A kilometer in the darkening distance,

      
The red tails slow and clump,

      
Brighten briefly, braking,

      
Then turn left into ebony oblivion.

      
Kilometers beyond,

      
The darkness deepens,

      
But on the rise of Andes mountains,

      
Can be seen the glimmering star-like lights,

      
Of human homes and sprawling city streets,

      
Dappling the hillsides with a twinkling spray,

      
Of mostly amber and white dots,

      
Interspersed with an occasional dull throbbing red,

      
And piercing bright blue.

      
These human lights are not stars,

      
And yet they resemble nothing more,

      
If not the sweeping pathway of a wide-splayed galaxy,

      
Mostly clumped in elongated array.

      
Yet, far beyond, in the utmost distance,

      
The furthest lights are sparsely grouped,

      
In the highest forested slopes,

      
Like angular, cryptic constellations:

      
Seven up—three across—two down.

      
Ironically, in the deep night sky above,

      
Not a single star or planet is visible.

      
The lights of space are totally obscured,

      
By dense Andean fog,

      
The haze of auto exhaust,

      
And a pale reddish glow of reflected city lights,

      
Like clouds of inter-stellar gas,

      
At the dawn of the Universe.

      
penned at the Hotel Rio Amazonas, Quito, Ecuador

Outside my hotel room lies Quito’s urban sprawl, enveloped in the Andes Mountains’ verdant, cloud-wrapped peaks. All of this starkly reminds me of the Cenozoic, our most recent geological era. Within the last sixty-five million years, tectonic forces uplifted the Andes, ultimately redirecting the water flows of South America and creating the Amazon River basin. The great diversity of modern neotropical plant and animal life was also shaped over the Cenozoic, and I’m in Ecuador with my students to search for previously unseen and undiscovered microscopic insects in the Yanayacu cloud forest—one of the most species-rich places on earth. Here in Quito, though, the urban chaos reminds me of another significant Cenozoic event: the evolution of the human species.

Were it not for the necessity of commenting on our origins and our impacts on this planet, I might not have bothered to write this chapter at all. You see, from my peculiar point of view as an entomologist, the mammals’ recent history seems almost like a trivial aside to the insects’ deep history, which, as we have seen, began hundreds of millions of years ago. Here, however, is my condensed version of the story
of us. One day, when the dust from the Late Cretaceous, dinosaur-extinguishing asteroid settled and the earth recovered her biological rhythms, some fortunate shrewlike mammals—insectivores, mind you—scrambled in the comfortable leaf litter, hunting for grubs. For the first time in 150 million years or so, they were
not
being hunted by the dinosaurs. Let loose from the bondage of dinosaur teeth, these small, furry, nipple-bearing, and milk-producing rodents proliferated. Some of these, the early lemurlike primates, evolved to occupy trees. They still ate insects, but some presumably expanded their diets and consumed fruit along with other plant parts. So it went for tens of millions of years, as our ancestors crawled from branch to branch, nibbling on bugs and plants. Then, between 5 and 12 million years ago (during the Miocene epoch), the climate of eastern Africa changed. From fossil pollen records we know that the forests in that region became sparse and grasslands more widespread. We suspect that some of the arboreal primates climbed back down out of the trees and started foraging, more omnivorously, for food on the ground.

Because many of our cultures still eat insects, we can assume that our highly omnivorous hominid forebears did so as well.
¹
They probably depended on bugs for protein just like chimpanzees, our nearest living genetic relatives. At certain times of the year chimps can spend up to seven hours a day feeding on termites, for which they fish by plucking a grass stem and inserting it into a nest entrance. The termites bite the stem then are easily extracted and eaten off of it (they’re protein pellets on the cob). Fishing with grass stems is probably the simplest imaginable form of primate tool use, and I think we can also assume that our ancestors shared this curious behavior with the chimps.
²
In my opinion, the origins of human tool use, fine motor skills, manual dexterity, and ultimately the rise of human civilization are firmly rooted in our ancestral insectivorous diets. We may owe our very existence to social cockroaches. If termites weren’t abundant, would primates ever have come back down out of the trees? I doubt it.

The Cenozoic years are popularly called the Age of Mammals, and you can probably guess why: because
we
are telling the story.
³
When humans discovered their own evolutionary history, the self-realization was almost too much to bear. The notion that we were not put here on a pedestal to rule the planet, but that we instead emerged from a long series of random and quirky events—that is a lot to contemplate.

What if Cambrian predatory arthropods had hunted our lowly ancestor,
Pikaia
, to extinction? What if Ordovician predatory sea scorpions, trilobites, and squids had eaten all of the early fishes? What if those scuttling Silurian and Devonian scorpions and centipedes had been so deadly as to prevent any vertebrates from colonizing land? What if during the Carboniferous the aquatic immature stages of the giant griffenflies had killed off all the immature stages of pond-dwelling amphibians? What if the Permian protomammals had been one of the casualties of the period’s mass extinctions? What if, at any time during the hundred million years of Mesozoic dinosaur domination, those toothy predators had managed to catch and eat the last of the little mammals? What if the Cretaceous asteroid had missed earth and the dinosaurs continued their reign of terror?

In each case, the answer is the same: if events had gone slightly differently, humans might not be here at all. The fact that we are here to ponder these things is truly awesome, but it is certainly not inevitable. We not-too-subtly reinforce our fragile human egos by continuing to call the Cenozoic era the Age of Mammals. However, mammals are indeed just one unlikely sidebar on the history of life. The Cenozoic world was still very much dominated by the insects and flowering plants. By focusing on the mammals we distract from what I see as the true success story of the most recent era: the origins and complexity of tropical forest ecosystems and their domination by insects.

Fifty Shades of Green

Notes from my Yanayacu diary:

We live in the Age of Tropical Biodiversity. The tropical forests of this Cenozoic earth are replete with thousands of flowering plant species and millions of insect species. Now I have been in the midst of this majestic biodiversity for one week. The forest at Yanayacu is a remarkable contrast to the street scenes in Quito. Here, during secluded moments deep in the cloud forest, one can almost imagine what the world might have been like had humans never arrived. Every day it rains at Yanayacu. Especially in the afternoon, and late at night, the raindrops pound the tin roof of the research station, sounding much like Wyoming hail on the metal roof of my beat-up old minivan. Now it is mid-afternoon on a quiet and unusually clear day. From my van
tage point in the station loft I can see, encircling the valleys, the moist forested hillsides of the Andes’s eastern slopes. The sounds of water splashing over rocks and gushing through narrow passages, dripping everywhere and splashing on leaves—the sounds of water along the stream trail are indelibly imprinted in my auditory memory. Water is everywhere and ever-present at Yanayacu. So much so, that the station dog is named Rain. Even in the rain, at night the blacklight sheet draws in thousands of moths. They cover the windows and walkways in the morning. The hyperdiversity of moth species at Yanayacu rivals that of any place on this planet.

A hike down the Yanayacu Stream Trail is a great way to appreciate Cenozoic tropical diversity. The trail snakes along the stream, crossing it many times. Sometimes we ford the stream on slick mossy stones, or wade in the cold mountain water. Sometimes we cross like acrobats on slippery algae-covered trees or boards laid loosely across the chilly water gap. On particularly rainy days, the stream rises, and you are sure to get plenty of cold water in your boots. Even on the trail the path is slick with mud and the way is sometimes treacherous. Above the water noise, sometimes we hear the piping and trills of unseen tropical birds—the most successful feathered Cenozoic dinosaurs—hidden in the dense foliage, or high in the forest canopy.

The forest is as green as it is wet. Even in the dim light of the understory, the forest is painted with riotous shades of green. Bluish-green to yellowish-green, lime green to olive, grass green to sea green, green in fifty shades and more, the color of an endless tropical summer, verdant and lush. Verde, green, the color of plants, the color of life: an ever-present reminder of the pigment chlorophyll, the stuff that allows plants to capture sunlight’s energy. Green, a constant reminder that our sun, our nearest star, provides this radiant energy for our terrestrial ecosystems.

Competition for sunshine fundamentally shapes the forest. The trees grow tall and spread their upper limbs to make a dense canopy, competing to filter much of that light in the highest layers. The light level at the floor is quite low, even at midday. In a mature tropical forest, 90–95% of the sunlight is filtered away by the plants before it can reach the ground. Some understory plants grow huge leaves, many feet across, to better soak up the filtered sunbeams. In small gaps in the forests, where old trees have fallen, more intense light briefly reaches
the surface. Young trees sprout rapidly from huge seeds that provide concentrated nutrition for the race upward. Most are wrapped, entwined in clinging vines seeking to make the same journey. The competition for sunlight, space, and nutrients is fierce, and only a few young seedlings will survive and mature to old forest canopy trees. Small epiphytic plants, like orchids and bromeliads, cannot hope to compete with the towering trees, so they stand on the giants’ shoulders: by sitting on branches, they get closer to the precious sunlight above. The density and weight of these epiphytic plants eventually becomes so great, it is not unusual for huge moss and orchid-laden branches to crack, and come crashing to the forest floor.

Along the Stream Trail the tree trunks soar high, like the pillars of a green basilica—the basilica of life. Quito is replete with human-built cathedrals, hundreds of years old, but I prefer the natural forest cathedral, millions of years old. All the trees are heavily matted with bromeliads, algae, lichens, and mosses. At close range, the surface of almost any log looks much like the mossy shoreline of a Silurian age stream—that miniature plant community where insects had their earliest terrestrial origins. These mosses still crawl with millipedes, centipedes, and microscopic wingless insects, as they have since the Late Silurian and Early Devonian. Along the path in the forest understory are ten-foot splayed tree-ferns, ancient survivors, reminiscent of the Devonian age forests where true insects first crawled, and later sprouted the earliest wings.