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The most influential species of all evolution

As we observe the 150th anniversary this month of the first publication of Charles Darwin’s On the Origin of Species, a new book reviews evolution and ranks the top one hundred most influential species of all time.

Homo sapiens is not at the top of the list.

In fact, we humans, who like to imagine that we are the masters of the universe, don’t even rank in the top five.

The most influential species (defined as the species that has most changed life on Earth) is … the earthworm.

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Photo courtesy USDA

“According to Charles Darwin, no living thing has had such a profound impact on history as has the earthworm,” says Christopher Lloyd, a history scholar at Cambridge University, UK, and author of What on Earth Evolved?: 100 Species that Changed the World (Bloomsbury, November 2009, $45).

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After considering the most important species that evolved before the ascent of human civilization, from the beginning of life on Earth until about 12,000 years ago, and then mulling all the species that have been successful since 12,000 years ago–that is the species that have flourished because of modern humans–Lloyd finds that he agrees with Charles Darwin: The earthworm is indeed the most influential species in the history of the planet.

Descendants of sea worms that existed five hundred million years ago, earthworms came ashore with the first invertebrate invasions of the land, making their living in damp soils broken up by bacteria, fungi and the roots of colonizing plants, Lloyd writes. “These earthworms have been ploughing up the earth, ventilating the soil and nourishing terrestrial ecosystems with their excrement ever since.”

The survivors of five mass extinctions, earthworms have had profound impacts on human history, Lloyd says.

“Were it not for their continuous regeneration of soils around damp river valleys such as the Nile, Indus, and Euphrates, early agricultural societies in Egypt, India, and Mesopotamia could never have succeeded in building humanity’s first large-scale urban communities.” 

“Wherever eathworms plough, people thrive. When worms perish, societies collapse.”

Throughout human history earthworms have unintentionally but undeniably triggered the rise of civilizations, Lloyd adds. “Wherever eathworms plough, people thrive. When worms perish, societies collapse.”

The European earthworm (Lumbricus terrestris) is probably the most prolific and invasive species in the world, Lloyd says.

“Its success is largely thanks to the spread of Europeans, c. 1600 onwards.

“Immigrant farmers inadvertently brought these earthworms, sometimes called ‘night crawlers,’ in everything from the soil in their potted plants and their horses’ hooves, to the treads of their boots and the wheels of their wagons.

“Today there is hardly a region of North America where Europe’s earthworms have not made a home for themselves. There they continue to plough, ventilate and fertilize the soil to the general benefit of life in and on the Earth.”

Before Man, After Man

What on Earth Evolved? is divided into two sections–Before Man and After Man. Starting with the early Earth, when loose strands of genetic code swarmed the planet, Lloyd explores the most significant lifeforms that evolved in the deep oceans and then wriggled ashore to become pioneers of life on land. In the second section, the author shows how co-evolution of humans and numerous other key species transformed Earth over the past 12,000 years.

A newspaper science and technology correspondent in a previous career, Lloyd has produced an accessible read, guiding the reader through capsule biographies of a hundred of the most influential species. They include slime, sea scorpions, dragonflies, potatoes, ants, tulips, sheep, dogs, cats, coca, opium, poppies, and grapes.

He ranks the species into a table of influence, revealing those that have most changed life on Earth. Academics will no doubt debate the selection and process, but Lloyd makes a compelling, albeit concise, case for each species. The full list of the hundred most influential species may be seen on the book’s Web site, or in the book itself.

Covering all of life in one book would be impossible, of course, but Lloyd has taken an interesting approach to some of the most marvelous products of evolution, leading to renewed appreciation of how much life has succeeded through both competition and collaboration.

Here is Lloyd’s top ten most influential species of all evolution:

Evolution’s top ten species

1. Earthworm

Made it possible for humans to cultivate the planet, settle, and build civilizations.

2. Algae

Without the countless forms of microscopic algae, larger forms of sea life would never have been able to evolve. All land plants are descended from ancestral forms of algae.

3. Cyanobacteria

Plants, trees, and animals all owe their existence to the presence of oxygen in the atmosphere and oceans, supplies of which were originally established by cyanobacteria, a photosynthesizing bacterium that breaks down carbon dioxide and excretes oxygen.

4. Rhizobia

Organisms capable of “fixing” atmospheric nitrogen into soluble nitrates that fertilize the soil so that plants and trees can thrive.

5. Lactobacillus

Bacteria that live inside the human colon, providing beneficial services such as assistance with digestion of milk and protection against harmful bacteria and organisms such as viruses and fungi.

6. Homo sapiens

Humans did not crack the No. 1 position on Lloyd’s list, but we merit five pages in his 416-page book and we are the only mammal in the top 10. We lose points chiefly as a result of our recent evolutionary emergence.

We may not rank as the most influential species in this analysis, but our impact pervades the past 12,000 years as we learned to farm animals and plants and harness mch of the resources of the planet.  In that time humans have had a profound impact on many other species, nurturing those useful to us and driving many that are of little value to us into isolation and even into extinction. Our impact on evolution is clearly in its early phases.

7. Stony corals

Coral reefs are powerful places for the natural conservation and co-operation of species, resulting in the construction of massive undewrwater mountains that house an extraordinary diversity of life.

8. Yeast

It is almost exclusively thanks to the action of this single-celled microscopic fungus that humanity has been able to enjoy everything from leavened bread to fine wine. Some of our best prospects for fuelling sustainable industrialization and transportation in the future are based on ethanol, a by-product of yeast.

9. Influenza

One of humanity’s biggest ever killers and still the largest threat to populations on Earth.

10. Penicillium

A naturally occurring antibiotic that has transformed modern medicine and substantially increased human populations.

Bloomsbury Publishing provided a copy of What on Earth Evolved? for this entry.

Comments

  1. Tristan
    May 15, 2011, 3:10 pm

    it is tough to compete with algae, here is a joke I saw about animals and evolution,
    http://ponderingstuff.com/2011/05/08/animals-in-landfills/