The Garden of Our Neglect: How Humans Shape the Evolution of Other Species

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For the vast majority of the history of our kind we were in some ways no more sophisticated than crows, which use sticks to poke around in promising holes. Eventually, of course, we discovered fire and invented stone tools, which then led to guns, pesticides and antibiotics. Using these tools, we encouraged the survival of favorable species such as wheat and yeast needed for beer and cows for meat and milk—a garden of delights. 


But we also encouraged a garden of neglect—a surprising number of resilient pests that have been able to survive in spite of our weapons. These species are now coming back to haunt us as toxins, pathogens or worse. Here are ten ways we have helped this garden of neglect prosper.

1. SHARP ROCKS, SOFT FLESH. In the beginning someone held aloft a sharpened rock. “Progress!,” he screamed out, or maybe, “Ouch!,” depending on which end he grabbed. With that first stone weapon and its many pointy descendants, life changed. Our initial impact would have been small. However, by 10,000 years ago we had extinguished many of the largest species on Earth—mastodons, mammoths, American cheetahs, giant kangaroos and many more. In our wake, we left behind smaller species more able to reproduce rapidly or escape detection in the first place.

As humans came to rely on tools to survive, those with hands better able to make and wield those tools were more likely to pass their genes to the next generation. Mary Marzke at Arizona Sate University in Tempe argues that hand bones of humans are quite different from those of other primates because of our use of tools. Our hands are better able to manage the subtle grips necessary for making and using tools to maim or kill other species. In response to our first tools the animals around us changed. So did we.

2. BIG FISH, LITTLE FISH. Not only have we altered the course of big game evolution on land but we’ve also effectively reduced the size of fishes in the sea. Fishermen prefer to catch big fishes, and fishing regulations tend to prohibit the harvest of the smallest individuals of a species. In response, fishes have evolved the ability to reproduce at a smaller size and/or younger age. If they can breed before they get big enough to be harvested their genes stand a much higher chance of being passed on. American plaice, Atlantic cod, Atlantic herring, Atlantic salmon, brook trout, and chinook salmon all have appeared to grow more slowly and/or to reproduce at smaller sizes where and when they are heavily fished (Jorgenson et al., 2007; Palcovacs, 2011) Once, a large cod could eat a small boy. Now, a small boy could almost eat an entire cod.

3. RESISTANCE IS FUTILE. Bacteria have been evolving in response to threats from other species, including fungi, for hundreds of millions of years. Bacteria and fungi compete for food and often do so using chemical warfare. A fungus evolves an antibiotic and bacteria evolve resistance, so fungi evolve a new antibiotic. Recently, though, things changed. We invented (or rather stole from fungi) antibiotics, which allowed us to kill bacteria—and, importantly, treat bacterial infections. However, by using them too much, too incompletely or too indiscriminately we cause bacterial strains resistant to our drugs to evolve. Unlike fungi, we cannot retaliate by simply evolving new antibiotics. Hundreds of bacterial lineages have evolved resistance to more than a dozen of our antibiotics. In response, we are forced to discover new antibiotics, an endeavor that has proved ever more difficult.

Written By: Rob Dunn
continue to source article at scientificamerican.com

11 COMMENTS

  1. Absolute power corrupts absolutely. Lets hope we can change before nature allows us to destroy ourselves. At our present rate of growth it shouldn’t take long unless we do something about it.

  2. My pet whimsical  theory is we’ll evolve to become a species of immortal logical donkeys. The alternative is to abandon progress altogether, and “live as “nature intended”.

  3. Human brains are short term tools far maximal personal advantage – as the dominant and predominantly described entropy: the most powerful defer to this model and thus the majority of those below them defer to it also as a survival and enhancement model of their own life.

    The war is waged due this, with everything that seeks to regulate and diminish it. Human brains not only adapted to subdue almost all species, save a few micro enemies, but themselves and everything that stands in the way of their subjugation. 

    Humans are the perfect adaptation for enslaving all surrounding organisms: Planet Earth’s premium slave traders; the most highly evolved brains compulsively obsessed in ensuring everything must die, or live, at my pleasure!

    Not until the barrel runs dry will the most well placed of these “top end food chain brains” consider alternatives: the irony fixed in position; that their short lives become the bane of all their subjects; it is only this that precludes them from considering the sufferings beyond the scope of their own privilege – during and beyond their relatively short lives – which is the topic in the OP: the few centuries of collateral damage! 

  4. Seems rather unlikely that humans “had extinguished many of the largest species on Earth
     Since the megafauna extinction of 10,000 to 12,000 years ago happened in North America and the northern Eurasian continent, and bypassed south Asia and Africa, it seems rather odd that humans in North America and north Eurasia would be able to wipe out the megafauna while their cousins in Africa left the elephants and giraffes standing. Are elephants that much harder to kill than mammoths?

  5. Elephants would have had the time to evolve a fear of man while our technology and skills improved. But the first Americans arrived suddenly with the technology, skills and experience. 

  6. The last Siberian mammoths hung on until around 4,000 years ago.on Wrangel Island, which was around the time the first men arrived.

    In PNG and Oz the demise of the megafauna again roughly coincided with the first men.

    The evidence is all circumstantial. But in North America the animals had managed to survive more than 20 ice ages and inter-glacials. To quote Jared Diamond- Men have been hung on less evidence. 

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