Sometimes our ignorance takes a while to be obvious. So we continue with a seemingly sensible behaviour until we are shown the illogicality and folly of it. The latest revelation comes from a number of international biological studies that show we are breeding down wild species by taking the best and the strongest while leaving the worst and the weakest to reproduce ‹ virtually the opposite of evolution's natural selection process.

We should have considered the inevitable consequences of our behaviour as "superpredators", the term Dr. Paul Paquet, a biologist from the University of Calgary, uses to describe our impact on nature. But, as usual, our judgment is clouded by self interest, immediate gratification, economics and a lack of perspective that fails to anticipate the long-term consequences of our actions So scientists once again, this time from Canada, Australia, Africa and America, are clarifying what should have been elementary and obvious.

In natural systems, predators normally take about 10% of a prey species, almost always culling the newborn, the weak, the sick and the old. In a target species that interests us, we can take as much as 50-60%, with a preference for those alpha individuals that are in prime condition. As a result of this unnatural selection process, we are "breeding down" or "devolving" these species to be smaller and less robust. This rate of devolution is estimated by biologists to be 300% faster than nature normally evolves them to be genetically superior ‹ pollution is also changing species at a rate 50% higher than natural selection (Globe & Mail, Jan. 23/09).

In a 30-year study of bighorn sheep at Ram Mountain in Alberta, for example, biologists found that trophy hunting of the biggest and best animals had reduced horn size by 25%, and that both males and females during that time were getting smaller because of the "removal" of the biggest and best breeders. The same findings are apparent in Norway with caribou, and in Australia where poachers target the largest red kangaroos for leather. Overall, of all wild animal species hunted by us, body size has diminished an average of 18%. Salmon, flounders, northern pike and Atlantic cod are also getting smaller. And in a dramatic example of devolution, catch records from the old settlement of Louisbourg in Nova Scotia reveal that the average size of a cod caught in 1750 was just under 50 kilos, a dramatic difference from the pitiful remnants that are caught today.

In almost every species we target, our preferences for the biggest and the best is also forcing down reproduction age. Again for Atlantic cod, the breeding age has fallen from six years to five, with a yield of egg masses that are smaller and less viable ‹ this is likely a factor contributing to the collapse of the cod populations and their failed recovery in East Coast waters. Scientists describe this change as being comparable to human children suddenly reaching sexual maturity and having offspring at nine to 11 years of age.

Our effect is being felt on more than animals. Equally dramatic is the response of wild American ginseng to persistent and intensive harvesting. Long prized as a treatment for numerous human ailments from cancer to Alzheimer's, the ginseng has not only changed composition but an increasing number of small plants have become non-reproductive (Globe & Mail, Jan. 23/09).

Even elephants are responding to human influence. Since tusks get them killed, a genetic fluke in African elephants has meant that a rare 2% that have no tusks has escalated to 38% in one Zambian population and 98% in a South African group (Newsweek, Jan. 12/09). In Sri Lanka the proportion of tuskless elephants has more than doubled to 90%. Tusked animals were "genetically better individuals" says biologist Marco Festa-Bianchet of the University of Sherbrooke in Quebec. "When you take them systematically out of the population for several years you end up leaving essentially a bunch of losers doing the breeding" (Ibid.).

Although devolution is a degenerating process, it is an adaptation to the stresses that we place on species. Unfortunately, it ultimately works against the viability of species ‹ it can weaken them enough to risk extinction ‹ and it doesn't work to our benefit either. The trophy hunter who carefully stalks and then kills a magnificent elk, moose, bighorn or grizzly has just removed those prize attributes from the gene pool and left lesser ones to reproduce. The result is an accelerating decrease in the supply of prize game.

This same devolution process is in action when we use coarse nets to selectively capture big fish and let the small ones escape, when we keep the largest salmon and release the smallest, or when we cut the tallest and straightest trees while allowing the dwarfed and crooked ones to live and reproduce. The practice ultimately works against our interests. Even worse, however, the adaptive response of species to the disproportionately high impact of our predation skews their attributes, thereby destabilizing the delicate balances that keep complex ecologies healthy and viable.

We think we understand. But our usual strategic failing is that we don't understand enough. And the limited judgment we do have is often compromised by ego, pride, greed, habit, power and convenience. If we are to continue assuming increased responsibility for managing our planet's complex ecologies, then each of us will have to think bigger and act smarter by considering the health of species other than ourselves. Under our new burden of responsibility, ignorance becomes even more expensive and even less excusable.