Natural Selection Gives Way to Human Selection

[wallacio]

http://www.theglobeandmail.com/servlet/sto...ry/Science/home

 

MARTIN MITTELSTAEDT

 

From Tuesday's Globe and Mail

 

January 13, 2009 at 4:15 AM EST

 

Humans have become "superpredators," speeding up the evolution of the species they hunt and harvest at rates far above what is found in nature, according to new research, some of it conducted by Canadian biologists.

 

The researchers believe that many recently observed changes in species, ranging from the shrinkage in the horns of bighorn sheep in the Rockies to the reduction in the size of caribou in Scandinavia, are being driven by humans.

 

The biologists estimate that hunting has caused such characteristics as body size and reproductive age to change at a rate that is a staggering 300 per cent above the pace that would prevail in nature. This figure is even greater than the change attributed to other human interferences, such as pollution, which was estimated to alter species 50 per cent faster than what normally happens.

 

"The implications are pretty wide and profound," said Paul Paquet, a University of Calgary biologist who dubs humans "superpredators" for this outsized impact.

 

A paper outlining the findings was posted yesterday in the online edition of Proceedings of the National Academy of Sciences.

 

In it, Dr. Paquet and others argue that current hunting and harvesting practices are inadvertently causing dramatic changes in the behaviour and appearance of species. The reason: Humans tend to "high-grade" nature, taking out the biggest and best in a species.

 

The approach is clearest in trophy hunting, where animals with the biggest horns or bodies are killed, while inferior ones are left. But the practice also occurs in commercial fishing, where mesh openings in nets capture the biggest fish while smaller ones escape.

 

The human approach is the opposite to what happens in nature, where predators kill the easiest-to-catch animals, such as the young, the old and the sick, but are unable to take out the fittest adults, which then reproduce and pass their desirable characteristics on to future generations.

 

Many hunting rules are based on a view that bagging mature animals is the best approach, but Dr. Paquet says humans should be trying to emulate nature, even though at first glance it doesn't seem sporting to kill younger creatures. "That's clearly the best management regime," he said.

 

The researchers, who are affiliated with the University of Calgary and the University of Victoria as well as two U.S. universities, looked at 34 studies that examined physical or biological characteristics in 29 species subject to heavy pressure from human predation. Besides the bighorn sheep and caribou, they included snails; a pair of medicinal plants; and various commercially caught fish.

 

"Harvested organisms are the fastest-changing organisms of their kind in the wild because we are superpredators and we take such high proportions of a population and target the largest individuals," Dr. Paquet said.

 

The rate of change is staggering from an evolutionary point of view, where the alteration in species is often thought to occur slowly. Alberta's bighorn sheep, for instance, have experienced a 20-per-cent drop in the length and size of their horns in only the past 30 years. The sheep are prized for the distinctive curve in their horns, making them sought-after trophies.

 

Atlantic cod, whose populations have collapsed because of overfishing, now reproduce at an average age of five years, rather than six, as was the case previously. The change, which in humans would amount to children reaching sexual maturity and having offspring at ages of around nine to 11, occurred in only two decades.

 

Among the species harvested or hunted by humans and reviewed in the paper, body size or horn size decreased by an average 18 per cent. There was also a pattern of reproduction at an earlier age or smaller size.

 

*****

 

THE DIMINISHING PREY

 

BIGHORN SHEEP

 

The sheep, found in mountainous areas of Western Canada and the United States, are famed for the unusual curved horns on the rams. The rams are hunted as trophies, but researchers believe the practice of taking the biggest specimens has prompted genetic change leading to a marked decline in horn size.

 

CARIBOU

 

Caribou from southern Norway, the last remaining wild population in Europe, have shrunk because of hunting. The selective killing of the biggest animals has led to a reduction in the size of bodies, antlers and jaws. Researchers suspect the same trend may have occurred in southern populations of caribou in Canada.

 

AMERICAN GINSENG

 

The gnarled root of the plant is prized for its medicinal properties - collected for illnesses ranging from cancer to Alzheimer's disease. But extensive harvesting has led to a change in the composition of wild stands, with an increased number of smaller, non-reproductive plants.

 

COD

 

The destruction of cod stocks has led to altered reproductive behaviour. The fish produce eggs at a younger age, but this early breeding has a big drawback. The early breeders are producing abnormally low numbers of eggs.

[xeon]

Im kinda questioning the article. The biggest animals would be the ones to breed first anyways right, so the genes are still going to be in the heard. Even the inferior animals might still be the offspring of the "trophy" animals, and the gene that makes the animals trophy might still be there. But then again im not a geneticist or biologist.

[Rizzo]

I've never been called a super-predator before. Now that Predator from the movie Predator, THAT was a super-predator

[rob v]

To some degree the study/theory seems to make a bit of sense. ... and tends to mimic what most anglers have preached in the recent past - keep the smaller "eaters" and let the big brood fish go to reproduce similiar offspring. Trouble is when you're hunting it's tough to practice catch and release !!

 

Perhaps hunting reg's need to be re-visited ? Fewer bull / cow tags ?

[solopaddler]

Interesting stuff Dave. I read a similar article recently where biologists were speculating that fish in a particularly popular lake were overall smaller 'cause they learned being bigger equated into being caught kept and killed.

Basically the exact same theory: that because of mans predation nature has evolved at an alarming rate to cope with the problem.

 

(I expect Lundboy will chime in on this one )

[TJQ]

Many hunting rules are based on a view that bagging mature animals is the best approach, but Dr. Paquet says humans should be trying to emulate nature, even though at first glance it doesn't seem sporting to kill younger creatures. "That's clearly the best management regime," he said.

 

SEE!! SEEE!! That why all my deer are smaller!! Im a super predator.

 

Interesting read.. reminds me of when I went caribou hunting in NF and the guide was telling me the racks were getting smaller, cause over the years all the males with big racks continued to get taken, thus only males predisposed to have a smaller rack were available for breeding.

 

(I know theres a strip bar joke in there somewhere...)

[solopaddler]

SEE!! SEEE!! That why all my deer are smaller!! Im a super predator.

 

 

HAHAHAHA!!

[Ramble]

the are talking about this stuff likes it new. this stuff has been around for YEARS. the big horn thing, is pratically dogma now-a-days.

 

This kind of selectionis affecting all kinds of things. i've seen papers about the behaviour of fish predisposing them to being caught leaving the remainder to be less agressive and slower growing.

 

The human selection is different then the natural selection or sexual selection, because we reomve the biggest and best.

 

The biggest animals would be the ones to breed first anyways right, so the genes are still going to be in the heard. Even the inferior animals might still be the offspring of the "trophy" animals, and the gene that makes the animals trophy might still be there. But then again im not a geneticist or biologist.

 

in a word "no". lol no offense.

Big horns and things like caribou have a heard structure. 1 male does the majority of maiting to a group of females. If you keep removing the biggest and best lesser quality males do the breading and water down the gene pool, and the traits end up being lost.

 

The traits may still be burried in the genetic code of the heard, but it would take selective pressure in the other direction to bring back the big males as they once were. You would have to kill off small males, and let the big males do their thing. It doesn't take a whole lot of time to shift traits one direction or the other with adequite pressure.

 

anyway, thats my 25 cents.

 

-R-

[danbo]

Yes Sir, man was given dominion over God's Creation. He sure done messed it up,eh?

[troutologist]

Great article! This kind of research interests me, I wish I was working on this type of thing.

 

Though I agree with the article, I was curious about a few things:

 

1. Since the majority of breeding is done by the "herd bull" is it safe to assume that the "lesser" males are his offspring, and thus containing the "trophy" genetics. This would imply that lesser bulls are simply immature and have the potential to grow into trophies.

 

2. With an observed trend towards mroe rapid change through human-induced pressures from various harvest techniques, how is it that each year new big game records are taken. I wonder if this can be attributed to mutations due to other human activities, pollution, hormones etc.

 

Just some ramblings of mine...any thoughts?

[Dano]

Interesting, it cerainly makes sense to me, modern man is brilliant at screwing the balance up.

 

I heard the average size beast in the herd was getting smaller.

[Ron]

Another theory you can add to this equation is:

 

If the largest of the species are harvested, the successors of the breed are maturing at a much younger age therefore creating no competition for "survival of the fittest".

[limeyangler]

Interesting read...thanks for posting.

[kemper]

Who is to say that this is not just 'evolution'.

 

We as humans are part of the evolution chain as well, we may have the traits that are required to become the dominant specie in the world but in truth we are also part of the animal world. It seems to me then, that as we evolve and force others into evolving at fast rates/ different patterns it is simply evolution. How do you think those animals got the big racks? Did something kill all the small ones? I doubt it, simply evolution.

 

I DO agree however, that we should be taking more care of our resources

[Rich]

This isn't really news.. more common sense than anything

[fishermccann]

Explains why there is a lot of short weak men out there with big wallets.

[Jigger]

Pretty linear thinking IMO. Pull a trophy moose every year and the genepool gets diluted. If I'm not mistaken, thats two record moose taken in 2008. Think that there are enough of the calves sired that make it to that same potential ultimate size? I don't.

 

At the same time, although the bighorns' rack may be shrinking, it seems like the mooses' haven't seen any...shrinkage.

[Ramble]

I've been keeping an eye on the post but haven’t been posting much, because I don’t want to argue or get anyone bent out of shape here. However, I’m going to weigh in again, and hopefully I don't step on anyone’s toes too badly.

 

 

Who is to say that this is not just ‘evolution’?

 

We as humans are part of the evolution chain as well, we may have the traits that are required to become the dominant specie in the world but in truth we are also part of the animal world. It seems to me then, that as we evolve and force others into evolving at fast rates/ different patterns it is simply evolution. How do you think those animals got the big racks? Did something kill all the small ones? I doubt it, simply evolution.

 

Evolution can come about from many kinds of selection. Sexual selection, natural selection or artificial selection as examples. Sexual selection occurs when mates are continuously choosing a mate with a specific characteristic for example the tails of the birds of paradise. Natural selection is the selection we are mostly familiar with. Creatures that possess the best traits for their environment at have the highest fitness level, and so a higher proportion of their genes are passed to the next generation. Artificial selection occurs when people select for various traits. The various dog breeds were brought about by artificial selection of various traits.

 

Evolution is all of these things. Evolution is NOT a predictor event, when I mean is, it isn't a "best guess" at what will be successful in the future, it simply responds to the selection pressure during the animals’ life, one day at a time.

 

People in the case of rams; have been artificially selecting rams for their largest horns. This lowers the fitness of rams with large horns. In other words they are evolving to have smaller horns, because the large horned animals are dying, and not passing on as many genes to the next generation, thereby lowering their fitness, and increasing the fitness of the smaller horned animals. Same idea with the European caribou in body. Large bodied animals are being killed of, so animals that are smaller proliferate in the gene pool, make the overall heard smaller in body size over time.

 

They are evolving is response to hunting pressure by humans. In natural selection bigger animals with larger horns dominated, and we are messing with that. The sheep had adapted to their habitat, and conditions based on natural selection of their environment. The sheep are now displaying an evolutionary shift which indicates artificial selection is now a major factor in their evolution. The point I believe of the article is displaying how we are working against the natural selection of the population. This may not be beneficial to the population and negative traits previously removed through natural selection, may now get a foot hold because of humans selecting animals which are the biggest and healthiest, giving unhealthy animals an ability to increase their fitness.

 

For the caribou this can have some serious implications. Rams loosing horn size, is mostly a problem for us who value them for their horns. It is unclear if other detrimental genes are being passed on due to the selection occurring. But the caribou body size is of concern. Animals in the north have a larger body size then southern relatives. It’s easier to retain heat if you have a larger body mass. Smaller animals need more calories to stay warm, and harsh winters may reduce population numbers. That is an example of how our artificial selection has the potential to mess with the health of the heard.

 

Pretty linear thinking IMO. Pull a trophy moose every year and the gene pool gets diluted. If I'm not mistaken, that’s two record moose taken in 2008. Think that there are enough of the calves sired that make it to that same potential ultimate size? I don't.

 

As far as moose go, there population is HUGE compared to the populations of the mountain sheep or European caribou. Moose from Virginia have been found in Ontario. The population spans the entire country, allowing for the flow of genes. This allows for extremely remote locations to be a "pool" for the positive genes in the population. There is also sexual selection at play for moose antlers, and even if lesser males are the only ones around, the antler size plays a role in the sexual selection. This continuously drives the moose populations towards large racks. SO basically the life history of the animal is insulation the effects artificial selection has on the racks of the moose.

 

As far as human evolution goes. We aren’t really evolving much anymore. Natural selection doesn’t really apply as we just use technology to adapt instead of adapting biologically. Sexual selection might play a role, but since there isn’t one preferred trait in our population, everyone likes different things, then that kind of cancels itself out. Best we can hope for is some sort of perverted artificial selection. The sad thing is that evolution is based on the fitness of mates. The more kids you have the more genes you pass onto the next generation. Stats show that more educated people are the fewer children they have. So it’s possible we could see a "dumbing down" of population if you assume that intelligence is a genetic trait which can be selected for.

 

It’s very difficult to apply some sort of selection process to people now-a-days.

 

Anyway I hope that helped you guys out with the how and why some of this evolution stuff works.

 

Feel free to criticize my response, and we can delve into this stuff a little further.

 

-Dave

[Ramble]

Another article on the subject.

 

 

http://www.cbc.ca/technology/story/2009/01...78065:b20599745

 

Human consumption speeding up evolutionary change: study

Last Updated: Monday, January 12, 2009 | 6:22 PM ET Comments19Recommend25CBC News

Humans are dramatically speeding up evolutionary changes in the plants and animals they hunt and harvest, according to new research.

 

Researchers from Canadian and U.S universities analyzed data from a variety of studies that examined trait changes — like those in antler size or reproductive age — of 29 species of organisms consumed by humans.

 

The study found that changes in organisms harvested by humans — among them fish, ungulates, invertebrates and plants — occur 300 per cent faster than they would in the organisms' natural environment.

 

This is because humans generally tend to "target large, reproductive-aged adults," says the study, which will be published in Tuesday's edition of the Proceedings of the National Academy of Science.

 

"Fishing regulations often prescribe the taking of larger fish, and the same often applies to hunting regulations," said lead researcher Chris Darimont in a statement. (CBC radio's Jan. 17 edition of Quirks and Quarks will have an interview with Chris Darimont.)

 

"Hunters are instructed not to take smaller animals or those with smaller horns. This is counter to patterns of natural predation, and now we're seeing the consequences of this management."

 

Animals are also breeding at a younger age and are getting smaller, the study says. Populations of some fish are on average 20 per cent smaller than 30 years earlier while other creatures are reaching reproductive maturity 25 per cent earlier.

 

"The public knows we often harvest far too many fish, but the threat goes above and beyond numbers," said Darimont. "We're changing the very essence of what remains, sometimes within the span of only two decades. We are the planet's super-predator."