Using evolution against itself

Using evolution against itself

Photo by Arjun MJ on Unsplash

Originally published 22 January 2002

It is a wide­ly held mis­ap­pre­hen­sion that evo­lu­tion is “just a theory.”

But, if three sim­ple con­di­tions apply to any self-repro­duc­ing organ­ism — vari­abil­i­ty, inher­i­tabil­i­ty, and selec­tion — then evo­lu­tion is not just a pos­si­bil­i­ty, it is a log­i­cal necessity.

These traits are man­i­fest­ly char­ac­ter­is­tics of life on Earth. Vari­abil­i­ty: Genes are sub­ject to ran­dom muta­tions, copy­ing errors, sex­u­al mix­ing, direct trans­fer of genes (between microbes), and, recent­ly, human engi­neer­ing. Inher­i­tabil­i­ty: Genes are passed to off­spring. Selec­tion: Some genes make crea­tures more fit to sur­vive and repro­duce than oth­ers. All of this has been exhaus­tive­ly demonstrated.

Under these cir­cum­stances, evo­lu­tion is inevitable. It would take the inter­ven­tion of a divine being to stop it from happening.

Not only has it hap­pened in the past, it is hap­pen­ing all around us today. In fact, evo­lu­tion by nat­ur­al selec­tion is one of humankind’s biggest problems.

Viral and bac­te­r­i­al pathogens, agri­cul­tur­al pests, and dis­ease-caus­ing insects out­wit our best efforts to con­tain them by evolv­ing defens­es against drugs and pesticides.

How quick­ly organ­isms evolve depends, among oth­er things, on how fast they repro­duce, which is why evo­lu­tion­ary biol­o­gists like to do their exper­i­ments with fruit flies, say, rather than sheep or corn. Although ani­mal and plant breed­ers achieve sig­nif­i­cant results on a scale of years, it is microor­gan­isms — repro­duc­ing in hours or less — that respond most rapid­ly to envi­ron­men­tal change.

Bac­te­r­i­al pathogens evolve resis­tance to antibi­otics faster than we can invent new ones. The major­i­ty of hos­pi­tal infec­tions are now resis­tant to peni­cillin, and many germs defy even stronger antibi­otics. Drug-resis­tant bac­te­ria are also com­mon on farms, where antibi­otics are fed to live­stock as a mat­ter or course.

Virus­es evolve even more quick­ly. Every year, flu shots must be refor­mu­lat­ed to keep ahead of an ene­my that won’t sit still. The AIDS virus evolves so fast that indi­vid­ual patients can har­bor dif­fer­ent variants.

Mos­qui­toes evolved resis­tance to DDT with­in 25 years of the dis­cov­ery of that insec­ti­cide, frus­trat­ing efforts to erad­i­cate malar­ia. It typ­i­cal­ly takes about a decade for an insect to evolve resis­tance to a spe­cif­ic insec­ti­cide. Weeds become resis­tant to her­bi­cides in about the same time.

All of this is the nat­ur­al response of organ­isms to human-induced changes in their environment.

We cur­rent­ly dump about 700 mil­lion pounds of pes­ti­cide into the envi­ron­ment each year in the Unit­ed States alone. Antibi­otics are mas­sive­ly laced into live­stock feed. Doc­tors over­pre­scribe antibi­otics to patients, and the drugs are often not used effec­tive­ly against their intend­ed targets.

The pests and infec­tious agents evolve defens­es with alarm­ing rapid­i­ty. Biol­o­gist Stephen Palumbi, writ­ing in the jour­nal Sci­ence, stat­ed: “Rates of human-medi­at­ed evo­lu­tion­ary change some­times exceed rates of nat­ur­al evo­lu­tion by orders of mag­ni­tude.” He esti­mat­ed the costs of coun­ter­ing evo­lu­tion by pests and pathogens to be approach­ing $50 bil­lion a year.

What’s to be done? Well, we could sim­ply give up the bat­tle and let the microbes, insects and weeds have their way, as they did before we dis­cov­ered how to fight them with tech­nol­o­gy. But, in a world crowd­ed with 6 bil­lion vul­ner­a­ble human beings, this is not an option. Is any­one pre­pared to accept today the mil­lions of deaths that occurred in the great flu epi­dem­ic of 1918? Can we sit idly by while AIDS rav­ages Africa?

What about elim­i­nat­ing those hun­dreds of mil­lions of pounds of insec­ti­cides and her­bi­cides that farm­ers annu­al­ly dump into the envi­ron­ment, and rely instead on organ­ic farm­ing? Cer­tain­ly, we should strive to min­i­mize the use of chem­i­cal and genet­i­cal­ly-engi­neered pes­ti­cides, but organ­ic farm­ing alone will not pre­vent famine in the teem­ing cities of the devel­op­ing world.

More fun­da­men­tal­ly, we could dra­mat­i­cal­ly reduce the num­ber of humans on the plan­et, but no one has fig­ured out how to crack that nut.

As Stephen Palumbi sug­gests in Sci­ence, the only real­is­tic solu­tion is to use evo­lu­tion­ary the­o­ry to thwart the abil­i­ty of pathogens and pests to evolve resis­tance. For exam­ple, farm­ers can use a dif­fer­ent pes­ti­cide on their fields each year, deny­ing pests time to evolve resis­tance to any one agent. Or sci­en­tists can look for ways to slow muta­tion rates in organ­isms. Palumbi lists a bat­tery of suc­cess­ful strate­gies for reduc­ing vari­a­tion, her­i­tabil­i­ty, or selec­tion with­in tar­get populations.

All of which are fur­ther esca­la­tions of our arms race with the crea­tures that harm us. No one can be sure what the out­come will be, but to do noth­ing is to accept increased human fatal­i­ties to famine and disease.

Arms races are always fraught with dan­ger, but what we have on our side is intel­li­gence. And the first step in an intel­li­gent response to the prob­lems posed by evo­lu­tion is to admit that evo­lu­tion is more than “just a theory.”

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