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The Death of Natural Selection

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My evening plan to read Harry Potter for the first time (I know!) was thwarted by Linton Weeks’s thought-provoking post on the right of plants to evolve. The post reports on the work of the Community Environmental Legal Defense Fund, a nonprofit that helps communities develop laws that recognize ecosystems as rights-bearing entities. The CELDF’s work is not unprecedented; in 2008 Ecuador granted nature the constitutional right to the maintenance and regeneration of its evolutionary processes. The associate director of CELDF explained: “fish and other species in a river may be recognized as having the right to exist and evolve.”

These are not the only efforts to protect species’ abilities to evolve. The International Union for the Conservation of Nature (IUCN), for example, defines wilderness areas as “protecting large mainly untouched areas where ecosystem processes, including evolution, can continue unhindered by human[s], including development or mass tourism.” Other environmental organizations are similarly concerned about species’ evolutionary opportunities.

That environmentalists are pursuing legal protection of nature’s right to evolve suggests that nature’s ability to evolve could be threatened or withheld. Can humans really stop evolution?

Darwin wouldn’t think so. In On the Origin of Species, he wrote:

It may be said that natural selection is daily and hourly scrutinizing throughout the world, every variation, even the slightest; rejecting that which is bad, preserving and adding up all that is good; silently and insensibly working, whenever and wherever opportunity offers, at the improvement of each organic being in relation to its organic and inorganic conditions of life.

Species are constantly evolving to changes in their environments. “Right to evolve” proponents are arguing something more specific, that species should have the right to evolve under certain environmental conditions. This contention prompts monstrous scientific and philosophical questions. Do species have the right to evolve without human interference? To undergo natural selection, not artificial selection? Is it even possible for humans to avoid affecting the evolutionary trajectories of other species?

Humans have long recognized their ability to select for certain traits in other species. Artificial selection, or selective breeding, explains the proliferation of domesticated plants and animals. It explains the difference between a Great Dane and Paris Hilton’s Chihuahua. Darwin used the familiarity of artificial selection to make his case for “natural selection” – the ability of biotic and abiotic non-humans to select for certain traits in other species.

If it profit a plant to have its seeds more and more widely disseminated by the wind, I can see no greater difficulty in this being effected through natural selection, than in the cotton-planter increasing and improving by selection the down in the pods on his cotton-trees.

But Darwin, and the scientists who followed him, believed that artificial selection occurred much more rapidly than natural selection:

We see nothing of these slow changes[of natural selection] in progress, until the hand of time has marked the long lapse of ages, and then so imperfect is our view into long past geological ages, that we only see that the forms of life are now different from what they formerly were.

Recent research in ecology and evolution refutes this idea. In one experiment, ecologists found that in the absence of insect herbivores, evening primroses evolved to flower earlier and produce less defensive compounds in only three generations. Such “rapid evolution” has also been observed in organisms ranging from zooplankton to soapberry bugs to finches. It seems that populations sometimes respond to selective forces in just a few generations.

The second way that Darwin distinguished natural selection from artificial selection was by the quality of its products. In his view, humans necessarily produced species of lesser quality than God’s Nature. He valued the art of nature over the artifice of humans:

How fleeting are the wishes and efforts of man! how short his time! and consequently how poor will his products be, compared with those accumulated by nature during whole geological periods.

Like Darwin, many environmentalists value the work of nature over the work of humans. Perhaps this explains their concern for species’ access to “natural” conditions – meaning conditions without humans – and, presumably, access to natural selection. In this context “artificial” selection has a negative connotation: artificial in the sense of a mimicked or inferior product. People love their Chihuahuas and tulips, and benefit from their corn and cows, but they want to protect the evolutionary autonomy of polar bears and narwhal whales.

This sounds fine. It sounds sensible, given our familiar categories: natural versus artificial, human versus nature, Chihuahua versus polar bear.

But is there a species, anywhere, with an evolutionary trajectory that has not been affected by humans?

If climate change is caused by humans, then no organisms can avoid selection resulting from human actions. Climate change impacts every corner of the globe. And species evolve in turn.

It is even difficult to take the human impact out of classic examples of natural selection. Take Wikipedia’s entry on natural selection:

A well-known example of natural selection in action is the development of antibiotic resistance in microorganisms.

Tricky. Humans created the selective force (antibiotics) and applied them to microorganisms. It seems the distinction between natural selection and artificial selection is a distinction between unintended and intended design. In the antibiotic example, antibiotics led to selective elimination of maladapted individuals from a larger population. Similarly, in the evening primrose example, ecologists removed insect herbivores from the plants, then the plants responded to the lack of herbivory. In the Chihuahua example, humans picked the Chihuahuas they liked best and bred them. The results of the antibiotic and primrose examples were not intended by humans. The results of the Chihuahua example were.

Few experiments directly compare the results of intended and unintended selection on one organism. (But see this one). Such comparisons could help ecologists better understand evolutionary processes and could help conservationists develop species that are better adapted to climate change or other stressors. Many environmental organizations already emphasize that genetic diversity will be important to species’ evolutionary potentials, and hence odds of survival. Why not breed for climate change resistant species?

The National Center for Science Education states that “The only difference between natural selection and artificial selection is whether the difference in reproductive success is driven by naturally occurring processes, or whether the selection is imposed by humans.” But microorganisms, and Chihuahuas, and even narwhal whales, are acted upon by many concurrent selective forces. Human actions constitute some of those forces, whether they are intended or not.

Unlike Darwin, who believed that humans’ creative powers were trivial compared to Nature’s, environmentalists believe that humans’ creative powers are unique; they believe that humans are so powerful and strange that their capacity to influence other species’ evolutionary trajectories surpasses the capacities of all other abiotic and biotic earthforms combined.

In the state park near my house in New York, deer prosper, favored by suburban development and the extirpation of large predators. These deer decimate plants in the forest understory. Changes in the plant community lead to changes in the animal community. Japanese stiltgrass and Norway maples compete with the trilliums and white oaks. European Starlings fly overhead, first brought to North America in 1890 by a man who wanted to introduce every bird species mentioned in the works of William Shakespeare. A neighbor walks by; his Chihuahua stops to relieve himself on the side of the trail.

The evolutionary trajectory of every species in my local park is affected both by the actions of humans and the actions of non-humans. We cannot deny the reality or the responsibility of being a part of other species’ environments, just as other species are a part of ours.

Should we despair that we cannot enforce another species’ right to evolve without us? Should we abandon all natural areas, seeing them as corrupted shells of what they should be? Or should we embrace our creative potentials, the potentials we share with the rest of the living and nonliving world.

We couldn’t avoid affecting the evolutionary trajectories of other organisms, even if we tried.

The views expressed are those of the author and are not necessarily those of Scientific American.

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