We humans are seriously ing with the planet. No, I am not talking about pollution here. Its even more serious - there are some serious evolutionary and genetic changes going on. Against the natural evolutionary system. It used to be that the bigger, stronger animals that prospered, and smaller animals were targeted. Most if not all wild species that humans are targeting for food are not only evolving - often with negative consequences - but are affecting other species too. Smaller in size, they are actually a bigger threat to their own survival as species.
WASHINGTON (Reuters) – Hunting and gathering has a profound impact on animals and plants, driving an evolutionary process that makes them become smaller and reproduce earlier, U.S. researchers reported on Monday.
Their study of hunting, fishing and collecting of 29 different species shows that under human pressure, creatures on average become 20 percent smaller and their reproductive age advances by 25 percent.
The human tendency to seek large "trophies" appears to drive evolution much faster than hunting by other predators, which pick off the small and the weak, the researchers report in the Proceedings of the National Academy of Sciences.
"As predators, humans are a dominant evolutionary force," said Chris Darimont of the University of California, Santa Cruz. "It's an ideal recipe for rapid trait change."
Darimont and colleagues calculated the rates of trait change with a metric called the "Darwin," after Charles Darwin, who developed the theory of natural selection to help explain evolution.
They studied changes in the size of fish, limpets, snails, bighorn sheep and caribou, as well as two plants -- the Himalayan snow lotus and American ginseng.
In virtually all cases, human-targeted species got smaller and smaller and started reproducing at younger ages -- making populations more vulnerable.
"Earlier breeders often produce far fewer offspring. If we take so much and reduce their ability to reproduce successfully, we reduce their resilience and ability to recover," Darimont said.
The findings fit in with other studies that suggest many fish are over-harvested.
"The public knows we often harvest far too many fish, but the threat goes above and beyond numbers," Darimont said in a statement. "We're changing the very essence of what remains, sometimes within the span of only two decades. We are the planet's super-predator."
Regulations meant to protect the young may in fact be helping drive this unnatural process, Darimont said.
"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," he said.
The shrinking size of fish due to their overexploitation has dire consequences for the recovery of depleted stocks, scientists have claimed.
Fishing drives natural selection for smaller fish that grow more slowly and have reduced reproductive potential.
These changes are genetic and therefore hard to reverse, scuttling the renewal of dwindling fish populations.
Details of the research were discussed on Saturday at a major science conference in Washington DC.
"Most fisheries are collapsing and many are on the brink of potentially irreversible loss," said Jeremy Jackson, of the Scripps Institution of Oceanography in California.
"There are massive evolutionary shifts going on in the remnant populations of fish. Large fish with huge reproductive potential are being replaced by smaller fish with diminished reproductive potential," he told the annual meeting of the American Association for the Advancement of Science (AAAS).
No reverse
David Conover, of Stony Brook University in New York found a two-fold change in productivity in Atlantic silversides within just four generations of fish.
"By selectively harvesting the largest fish, we end up changing the whole biology - not only growth rates, but egg size, fecundity, feeding behaviour," he said.
"The scary part is that when we stopped size-selective harvest, the biology didn't change back, it was permanent."
Research by Dr Conover and other groups in Norway, Canada and Austria also found declines in the reproductive potential of fish populations.
Work by Steven Berkeley, of the University of California-Santa Cruz, shows that older and therefore bigger female Pacific rockfish produce exponentially more eggs than younger, smaller females and their larvae have a greatly increased chance of survival.
Safe haven
"What we need to provide is some refuge from fishing so that the genes for larger, faster-growing fish have some sanctuary from fishing," said Dr Berkeley.
Andy Rosenberg, of the University of New Hampshire, said that the way fish resources were currently being managed was prolonging the period of recovery for stocks.
"The longer we ignore these fine-scale processes, the longer it will take for that recovery. And it's not a simple linear relationship - you can cause massive damage in a very short period of time and it can take them much longer to recover," he said.
Cod off the coast of Newfoundland - once one of the largest fish populations in the world - have suffered a 99% decline since the 1960s.
Research shows that changes in size and age at maturity caused by just 30-50 years of fishing have reduced the chance of cod's recovery by 25-30%.
Whale sharks spotted off the coast of Australia are getting smaller, researchers have said.
In a decade the average size recorded by observers has shrunk from 7m to 5m.
Whale sharks, the world's largest fish, are caught for food in some east Asian countries and Australian researchers suspect this is causing a decline.
The fish is listed as "vulnerable", and one of the authors of the new study has described the new finding as "a very worrying sign".
The data comes from ecotourism companies which run expeditions to watch whale sharks and swim with them in Ningaloo Marine Park off the north-west coast.
"The eco-tourism industry logs the position and size and sex of every shark it swims with," said Mark Meekan, of the Australian Institute of Marine Science (Aims).
"We have obtained those datasets and analysed them over time," he told the BBC News website, "and essentially what we have seen in the last decade is a decline in average size of shark from 7m to 5m.
"Now, if you consider that the sharks probably aren't sexually reproductive or mature until they're 6 or 7m long - that's a very worrying sign."
Looking for options
Whale sharks (Rhincodon typus) are filter feeders, eating small marine organisms such as krill.
They can live for up to 150 years, attaining lengths of more than 15m, and are believed to reach sexual maturity around the age of 30.
Whale shark, Image: Rachel T Graham
The fish are placid filter-feeders
Under the IUCN Red List of threatened species, they are categorised as "vulnerable" to extinction.
"Whale sharks, like many other shark species, are highly vulnerable to over-exploitation due to their long lifespan and low reproductive rate," commented Callum Roberts, of York University in the UK, who has researched whale sharks extensively in the Caribbean.
"They have been added to CITES' list of species threatened by international trade," he told the BBC News website, "but this will not protect them if they are caught by, for example, Taiwanese vessels and then consumed in Taiwan.
"So whale sharks are at risk, and the decline in size might be due to capture of large sharks."
There are also indications that the number of sharks visiting Australian waters may be decreasing, which would be additional evidence for a decline prompted by over-fishing.
Playing tag
Aims researchers are running a tagging programme in an attempt to plot whale shark migration routes between Australia, Asia and the eastern coast of Africa.
Specimens tagged in Australia have swum to Asian waters; last month a tag transmitted for days from the same location in Indonesia, apparently on land, leading researchers to suspect that the shark had been caught and the tag removed.
Either the meat is eaten, or the giant fins used as advertising boards for restaurants serving shark fin soup; livers are used for oil, and cartilage in traditional Chinese medicine.
Finding migration routes could help pinpoint areas where they are being caught.
"Many of the people doing the fishing are just local villagers with no other option," said Mark Meekan.
"If we know who they are, we can give them another option, and that option is very lucrative; the ecotourism industry in Ningaloo generates AU$70m (£28m; US$50m) a year, enough to support an entire town."
Longer term objectives of the Aims programme include finding out more about the life cycle of the whale shark.
The biggest mystery concerns breeding and reproduction; males and females live in largely segregated communities, but must come together somewhere to breed.
They are believed to bear live young, but sightings of pups are extremely rare.
Psy-T
quote:
Originally posted by Magnetonium
We humans are seriously ing with the planet. No, I am not talking about pollution here. Its even more serious - there are some serious evolutionary and genetic changes going on. Against the natural evolutionary system. It used to be that the bigger, stronger animals that prospered, and smaller animals were targeted. Most if not all wild species that humans are targeting for food are not only evolving - often with negative consequences - but are affecting other species too. Smaller in size, they are actually a bigger threat to their own survival as species.
it used to be, so what? apparently, the older model (in which 'size mattered') is no longer equally valid.
who's to say our affect on this planet is necessarily negative?
Magnetonium
quote:
Originally posted by Psy-T it used to be, so what? apparently, the older model (in which 'size mattered') is no longer equally valid.
who's to say our affect on this planet is necessarily negative?
Fish are getting smaller - i.e. less food for their natural predators - it affects them too, less food for us as well. Plus its not just about size - it affects other spects of fish like reproduction. Its a trend thats not seen its end yet. Considering that demand for fish is increasing, and world population is still growing ...
Humans arent just affecting the environment this way. There's also light pollution, contamination of the environment with GM organisms, human-driven species extinction, as well as serious changes in species from pharmaceuticals and hormones released by humans in the biosphere. I can put up articles on those too.
Even that - its a tip of the iceberg of the real problem at hand. The one that is still not being addressed. Because people look at single problem and dismiss it, like you just did.
The damage / effect caused is PERMANENT, its not like you can just stop and things go back to the way they were. Thats why this situation is very serious. Have you read the articles?
Psy-T
quote:
Originally posted by Magnetonium
Because people look at single problem and dismiss it, like you just did.
that's not what i meant. i'm not dismissing this one problem due to my perception of it, i'm dismissing the entire spectrum of these kinds of problems.
quote:
Originally posted by Magnetonium
The damage / effect caused is PERMANENT, its not like you can just stop and things go back to the way they were. Thats why this situation is very serious. Have you read the articles?
let's scroll back before humans, look at dinosaurs as supreme predators (for example, any other would do, doesn't even have to be an animal, a point in time is sufficient) - could you 'just stop' and have things go back to the way they were before the dinosaurs (or any other arbitrary example)?
time only goes one way, there's no turning the wheel back regardless of how minor or major the events that took place are.
changes occur, does it really matter whether we cause these changes, prevent them, or simply observe them? don't you think it's a bit presumptuous of us to evaluate these changes and their effects with 'absolute certainty'?
The17sss
we should all just commit suicide so the planet can be whole again :rolleyes:
Seriously though, it is a little troubling. I watched a Nat Geo thing a few weeks ago about the Bluefin tuna... they used to be so much bigger and plentiful 50 years ago, and at the massive fish markets in Japan the old timers were saying maybe once a year you'll be lucky to see a really big one.
Unfortunately, this makes too much sense:
Magnetonium
quote:
Originally posted by Psy-T
that's not what i meant. i'm not dismissing this one problem due to my perception of it, i'm dismissing the entire spectrum of these kinds of problems.
let's scroll back before humans, look at dinosaurs as supreme predators (for example, any other would do, doesn't even have to be an animal, a point in time is sufficient) - could you 'just stop' and have things go back to the way they were before the dinosaurs (or any other arbitrary example)?
time only goes one way, there's no turning the wheel back regardless of how minor or major the events that took place are.
changes occur, does it really matter whether we cause these changes, prevent them, or simply observe them? don't you think it's a bit presumptuous of us to evaluate these changes and their effects with 'absolute certainty'?
I see your point - and I am not blaming the situation on any persons around here for anything, just food for thought. Many conclusions and ideas can be drawn up from the articles, but in either case - its a concern. What happened with dinosaurs and what they did - thats natural evolution. Humans are very different, what we are doing is often completely opposite of the natural order. We need to get a grip on ourselves as a species. It cannot be done on an individual level, people in power need to come up with solutions fast and soon, because there are many issues and hardly any of them are being tackled in any effective way.
Magnetonium
Here's another serious threat to human genetics and evolution - men might become extinct in the future - only women will be left:
The male gender is in danger -- with incalculable consequences for both humans and wildlife -- startling scientific research from around the world reveals.
The research, detailed yesterday in the most comprehensive report yet published, shows that a host of common chemicals is feminizing males of every class of vertebrate animals, from fish to mammals, including people.
Backed by some of the world's leading scientists, who say that it "waves a red flag" for humanity, and shows that evolution itself is being disrupted, the report comes at a particularly sensitive time for Britain. Yesterday, Britain led opposition to proposed new European controls on pesticides, many of which have been found to have "gender-bending" effects.
It also followed hard on the heels of American research that shows that baby boys born to women exposed to widespread chemicals in pregnancy are born with smaller penises and feminized genitals.
"This research shows that the basic male tool kit is under threat," says Gwynne Lyons, a former government adviser on the health effects of chemicals, who wrote the report.
Wildlife and people have been exposed to more than 100,000 new chemicals in recent years, and the European Commission has admitted that 99 per cent of them are not adequately regulated. There is not even proper safety information on 85 per cent of them.
Many have been identified as "endocrine disrupters" - or gender-benders - because they interfere with hormones. These include phthalates, used in food wrapping, cosmetics and baby powders among other applications; flame retardants in furniture and electrical goods; PCBs, a now banned group of substances still widespread in food and the environment; and many pesticides.
The report, published by the charity CHEMTrust and drawing on more than 250 scientific studies from around the world, concentrates mainly on wildlife, identifying effects in species ranging from Arctic polar bears to the eland of the South African plains, and from whales in the depths of the oceans to high-flying falcons and eagles.
It concludes: "Males of species from each of the main classes of vertebrate animals (including bony fish, amphibians, reptiles, birds and mammals) have been affected by chemicals in the environment.
"Feminization of the males of numerous vertebrate species is now a widespread occurrence. All vertebrates have similar sex hormone receptors, which have been conserved in evolution. Therefore, observations in one species may serve to highlight pollution issues of concern for other vertebrates, including humans."
Fish, it says, are particularly affected by pollutants as they are immersed in them when they swim in contaminated water, taking them in not just in their food, but through their gills and skin. They were among the first to show widespread gender-bending effects.
Half the male fish in British lowland rivers have been found to be developing eggs in their testes. Female hormones - largely from the contraceptive pills, which pass unaltered through sewage treatment - are partly responsible.
Scientists at Cardiff University have found that the brains of male starlings who ate worms contaminated by female hormones at a sewage works in south-west England were subtly changed so that they sang at greater length and with increased virtuosity.
Even more ominously for humanity, mammals have also been found to be widely affected. Two-thirds of male Sitka black-tailed deer in Alaska have been found to have undescended testes and deformed antler growth, and roughly the same proportion of white-tailed deer in Montana were discovered to have genital abnormalities.
Most alarming for humans, new research at the University of Rochester in New York state shows that boys born to mothers with raised levels of phthalates were more likely to have smaller penises and undescended testicles. They also had a shorter distance between their anus and genitalia, a classic sign of feminization.
Communities heavily polluted with gender-benders in Canada, Russia and Italy have given birth to twice as many girls than boys, which may offer a clue to the reason for a mysterious shift in sex ratios worldwide. Normally 106 boys are born for every 100 girls, but the ratio is slipping. It is calculated that 250,000 babies who would have been boys have been born as girls instead in the U.S. and Japan alone.
And sperm counts are dropping precipitously. Studies in more than 20 countries have shown that they have dropped from 150 million per millilitre of sperm fluid to 60 million over 50 years.
pkcRAISTLIN
while i consider myself an environmentalist of sorts, i cant say im too fussed about whether the human race will be able to breed in 10,000 years.
Clovis
quote:
Originally posted by Psy-T
who's to say our affect on this planet is necessarily negative?
Because the pace of our effect is in almost all cases far too quick for evolution to catch up.
We are completely flying in the face of millions of years of evolution.
