Moselio Schaechter

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June 30, 2011

Talmudic Question #76

Do you think that our species is exempt from "kill-the-winner" predator-prey dynamics? (KTW is the colloquial term for the cyclical dynamic by which phages promote community evenness by reducing the numbers of the most abundant bacterial strains.)


I wouldn't say that we as a species are exempt from kill-the-winner dynamics, but we are certainly testing it. After all, we bring something to the table which no other species does: our intelligence and technology. Of course, predators are not the biggest threat to the human race. We are as likely to exhaust our resources and poison our environment with waste products thus threatening our own existence (as yeast does in fermentation) before a microbial predator takes us out.

Barry and Brooke,

Right on! We're a young species, and our population density continues to increase, likewise our dependence on high-density monocrops. Add to that modern travel carrying any bug around the globe in a matter of days, if not hours, the millions of uprooted refugees, and the increasing number of people living without safe water to drink, and we seem to be creating opportunities for both viruses and Bacteria. Neither are known to let opportunities pass by.

I think the abundance of human pathogens that pop up in over-populated, over-cropped, over-lived areas is a good indication that our population control is out of our hands (and has been for thousands of years)!

Like SARS, if there's a virus that does not infect humans, it has the ability to evolve and quickly jump to humans, especially if there is a greater number of people around. Just like phage that have tropism for specific bacterial species - if there is a great number of that species around the phage, it will eventually evolve mechanisms to invade that new species.

On a smaller scale than that to which the above comment refers, how about considering individual, isolated groups. Families that are successful enough to outcompete other families are then prone to demise from inbreeding. Middle eastern ruling families, anyone?

Hi, Erika,

Indeed, this same notion can be applied at many different levels, driven by many different mechanisms. However, at least in a biological context, kill-the-winner specifically refers to the cyclical dynamics of predators and their prey. An increase in the prey population (the winners) leads to an increase in the predator population, and the numerous predators then reduce the prey population. With fewer prey, the predators in turn die back to a smaller population, allowing the prey population to increase once again. So although in-breeding could lead to a decline in those families, this is not kill-the-winner dynamics.


Not from Phage, but before Petroleum, we were periodically suscepible to population collapse due to our population dense lifestyles encouraging epidemics, and our symbiotic relationship to monocrop grasses. I suppose we are still susceptible. Our population boom has only been here for 10 to 40 thousand years.

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