From Dr. Susan Crockford’s Polar Bear Science
Posted on September 8, 2021 |
A new paper published today deals with an animal conservation issue I’ve addressed twice before: the theoretical assumption that loss of genetic diversity must be detrimental to species survival despite there being little evidence that this has been the case in real life. For this new study, the authors carried out some complicated measuring of genetic diversity loss and inbreeding amongst and between Svalbard region polar bear populations between 1995 and 2016 (see map below), and then modelled what this could lead to in 100 generations (1210 years), with the over-anxious hand-wringing we’ve all come to expect from such prophesies. As far as I can see, it’s all meaningless number-crunching without relevance to the real world of polar bears.
To support their claim of harm from loss of genetic diversity, the authors of this paper (Maduna et al. 2021) cite four theoretical papers that assume as fact that loss of genetic diversity is harmful but not the evidence to back up the claim. They apparently never bothered to look at species that have actually suffered dramatic loss of genetic diversity. Northern elephant seals, for example, reduced to 20-30 animals more than 100 years ago, have rebounded to a population of about 170,000 with extremely low genetic diversity but no apparent health or survival repercussions. Similar genetic bottlenecks and recoveries have been documented in Guadalupe fur seals, San Nicolas Island foxes, mouflon sheep, and North Atlantic right whales (among others), which I discussed in detail here (with references). I discussed the issue again in regards to a similar polar bear ‘genetic diversity’ paper in 2016.
Conspicuous by its absence in this new publication is a citation of the recent paper that revealed the body condition of female Svalbard polar bears had increased significantly between 2004 and 2017 despite a pronounced decline in summer and winter sea ice extent (Lippold et al. 2019: 988). Nor did the paper cite data collected by the Norwegian Polar Institute that show the body condition of adult males in Svalbard has not changed since 1993 or that population numbers have not declined. Instead, the authors mention only that reduced numbers of pregnant females have reached traditional denning areas due to lack of ice and that bears have spent less time feeding at glacier fronts than they used to do (Maduna et al. 2021: 2), as if the only polar bear data available in relation to sea ice decline was negative.
Population bottlenecks during the Last Glacial Maximum when suitable habitat was scarce and another in the late 1800s/early 1900s due to wanton overhunting left polar bears with remarkably low genetic diversity but no apparent ill-effects to their overall heath. Oddly, this recent work by Maduna and colleagues assumes without evidence that a bit less genetic diversity could be devastating to Svalbard bears more than 1000 years from now. While the media expectedly promote this as scary new evidence of what climate change has wrought (here and here), I am not impressed.
This is conservation biology done WWF-style: loss of genetic diversity sounds bad to people who don’t know better, but real-world evidence shows it isn’t.
References
Lippold, A., Bourgeon, S., Aars, J., Andersen, M., Polder, A., Lyche, J.L., Bytingsvik, J., Jenssen, B.M., Derocher, A.E., Welker, J.M. and Routti, H. 2019. Temporal trends of persistent organic pollutants in Barents Sea polar bears (Ursus maritimus) in relation to changes in feeding habits and body condition. Environmental Science and Technology 53(2):984-995. https://pubs.acs.org/doi/10.1021/acs.est.8b05416
Maduna, S. N., Aars, J., Fløystad, I., Klütsch, C. F. C., Zeyl Fiskebeck, E. M. L., Wiig, Ø. et al. 2021. Sea ice reduction drives genetic differentiation among Barents Sea polar bears. Proceedings of the Royals Society B 288 (1958): 20211741. https://doi.org/10.1098/rspb.2021.1741 OPEN ACCESS
It is a general and well established principle that genetic diversity allows a population to adapt genetically to a changing environment or to buffer it against stochastic events such as harsh weather or disease outbreaks. Both inbreeding depression and loss of genetic variation can also lead to an increased risk of extinction.
Svalbard is rapidly warming -it recently had a year of averaging above zero C and has had mudslides and other effects of thaw. Also the ice now usually retreats early and distantly from its shores. These are factors definitely showing a changing environment and stressing the population: loss of diversity is likely to be hindering its response.
What did these poor polar bears as it was warmer than now ? Any idea ?
Did you read and understand the papers ?
Griff has been asked many times how Polar Bears survived the Holocene Thermal Optimum. He has never replied.
He can’t 😀
maybe the only keystrokes he knows are CTRL-C and CTRL-V ☻
Keys aren’t the only thing Griff strokes.
“rapidly” “early” “distantly”
You like words that don’t have to be backed up with numbers. What about the reports of catastrophic Arctic warming in 1822?
High school stuff, show your work GriffinMonster…
I notice he’s not doing the Arctic sea ice extent retard dance any more. Looking very strongly like there will be 11 years below this years minimum, just like a real scientist on here predicted 3 weeks ago.
Wow, you managed to cut&paste that without screwing it up, still lies. Climate is just fine, no emergency and the only problem is greentards like you screeching and spewing lies about it.
Griffy – it is a general and well established THEORY that genetic diversity allows a population to adapt genetically to various changing events. There is absolutely zero evidence to support this theory and, in reality, the only reason the idea is still doing the rounds is because it’s supporters state that the right conditions just haven’t happened yet. The fact that many species are thriving and increasing their populations despite low genetic diversity should be a clue to even the hardest of heads that it just might not be entirely correct.
I was once told that there was more diversity in a troop of African baboons than in the whole of the human race , which ,itself became severely constrained according to Wikipedia
According to the genetic bottleneck theory, between 50,000 and 100,000 years ago, human populations sharply decreased to 3,000–10,000 surviving individuals.[32][33] It is supported by some genetic evidence suggesting that today’s humans are descended from a very small population of between 1,000 and 10,000 breeding pairs that existed about 70,000 years ago.[34][35]
Well that didnt seem to do us a great deal of harm and the only real threat to our continued occupancy of planetary top spot is an unwholesome obsession with AGW , which obsession may well be the death of us and will someome please tget that across to XR and agenda 21 loonies
Nevertheless, epigenetic is possible.
Your DNA from birth is different than in death. Many, many people don’t want to accept that.
In spite of natural selection being suppressed by modern medicine, human ability to endure a pandemic is on full display over the last 18 months. In fact I would go as far to say it is a natural correction to eliminate the less genetically healthy thereby increasing the survivability of future generations.
Tom, you would be wrong if you said that. The folks dying from FauciFlu (allegedly) are seniors well past their breeding years. Their genes did NOT get eliminated. Their blood lines did NOT get Darwinized. Unless they were LGBTQWERTY, in which case they genetically self-Darwinized decades ago.
Correction, Tom: natural selection was NOT eliminated by medicine nor by any other social human activities. Medicine works over natural selection. Mike Dubrasich made the point, and I add something. Natural selection is NOT a metaphysical force that exists in nature and act UPON the living beings: it is a CONSEQUENCE of the existence of living beings, as well as gravity is not a force external to matter, but results from the very existence of matter. Gravity is one manifestation of the mode of existence of matter: likewise, natural selection is a manifestation of the mode of existence os living beings, not a (metaphysical) force external to them, acting on them. So, natural selection can only be perceive through outcomes. Mike Dubrasich has pointed to perhaps the most significant: fitness, that is to say, se persistence in descent of the characteristics of parents. He points to the fact that most covid victims are old and passed the reproduction age. But, returning to what you wrote, medicine did not eliminate a lot of (mainly) genetic diseases that kill before the age of reproduction (thus preventing the transmission of characteristics to the descent). So, medicine, and other social human practices, do no eliminate, but instead act “over” (say: at another “level”) natural selection.
I saw a documentary on that some years ago that tried to tie it in to a potential disaster scenario that wiped out the rest of the human race at that point. I simply can’t remember what the conclusion was but that was the first time I’d heard of the bottleneck theory as well.
Was that the Toba [Tooba??] event?
Large volcano, much dust; poor growing seasons?
Not sure how that affected non-human animals [prey, etc.].
Or, indeed, our Neanderthal & Denisovan cousins.
Auto
Many if not most other species have large levels of diversity with close relatives exhibiting significant differences.
Close relatives that are considered different species.
Humans are unusually similar with extremely minor differences.
A similarity evident in the human genetic code, so that yes, a very small population survived some cataclysmic event.
That cataclysmic even had to be recent enough that no significant
genetic variation has evolved.
That cataclysmic event had to be far enough back in time to precede humans leaving Africa.
All of the variables going into that calculation, how many people, how many females, how many males, how long ago and exactly what was the event are all results of speculation with some calculus and statistics thrown in.
It could have been a very small group of survivors.
It could have been a tribe or two of survivors.
It is unlikely to be much larger amounts of people or greater genetic diversity would have survived. Especially considering how humans and their family groups formed societies and interacted with other societies.
Then there is the minor fact that human genetic code contain genetic pieces of all the ancestors leading to humans.
As do polar bears.
Both humans and polar bears have all the genetic codes necessary to handle almost any condition they encounter.
“Well that didnt seem to do us a great deal of harm”
Seriously? I never cease to be amazed at the abject crapness of humans.
You can thank the Toba eruption for that!
The Great Flood might be responsible? 🙂
Richard, you don’t understand, this is consensus science, and consensus science simply can’t be wrong.
As to the idea that mudslides in Svalbard are signs of a changing environment – utter crap. Svalbard, Norway and other areas in the Arctic circle regularly experience landslides – it happens almost every year, the most recent bad incidents were in 2016/17 when a road had to be closed and in 1972. The fact that it mainly happens around the Longyearbyen valley says much more about the geology of that area than anything else.
I wasn’t aware, that polar bears have to adapt genetically to land- / mudslides.. Will he say they have to learn to “swim” in the sliding mud ??? 😀
Just curious 😀
I simply cannot believe the ignorance on display here today. Krishna Gans; Polar Bears don’t swim in mudslides – they are very intelligent and have learned to surf in order to chase and catch prey in difficult conditions because, as we all know, Charlie the seal don’t surf!
With better genetic diversity, they would have learned to surf by now.
… or this is the only area on Svalbard where there are human observers.
I think you had better head back to the Daily Mail, you get less negatives there!
griff, “genetic diversity” is why you are allowed to continue posting nonsense here.
Griffy is from the bit near the drain filter in the gene pool!
Grrrr it’s that alarmist griff again
Give the bear scare a rest. It’s worn out
Who cares what the actual data shows. The consensus is that any decrease in genetic diversity is devastating and can lead to extinction.
Since the environment that the polar bears are experiencing is well within the norm for the last 10 to 15 thousand years, why should they have to “adapt” to it?
So what, griff?
Among the many things that are “established principles” you never heard that the cost of adaptation is losing some diversity? I.e., organisms adapt losing some characteristics while acquiring others!
Have you seached your own DNA, griff? Have you found there some genes from trilobites? Joking, they are not in your phylogenetic ancestry, I suppose… but, seriously, did you find any genes from synapsids or cynodonts? Quite difficult, hu!… you know, between cynodonts and you, there has been A LOT of loss of genetic diversity!… Yes, believe it or not, it’s an “established principle”.
“It is [also] a general and well established principle that genetic diversity…” [is more complex, with exceptions.] Introduced whooping cranes in Louisiana are breeding, success to be determined both in Louisiana and east Texas. Many were positive it couldn’t genetically happen. Increasing migratory flock spreading from refuge, better watch out for windmills still coming in. One blade on a truck just got clobbered in Luling, Texas by a train. Happened to have had occasion to make that corner many times with a 26′ trailer, not easy. We already knew that those pushing windmills were not very smart.
Nope.
Wrong again.
Human genetic code contains snippets of all the creatures humans evolved from.
The result is an incredibly large complex genetic code with an immense amount of variation to handle just about any situation humans encounter.
The same goes for polar bears.
Griff would like us to know that though he diligently writes this stuff he doesn’t really understand a word of it.
The Grifter did not write that, it’s a cut and paste from at least two different sources.
This for example:
“Genetic diversity allows a population to adapt genetically to a changing environment or to buffer it against stochastic events such as harsh weather or disease outbreaks.”
is copied directly from the abstract of a forum paper on “Managing genetic diversity in threatened populations” New Zealand Journal of Ecology volume 32 (2008).
If you copy and paste without acknowledging the original author it’s called plagiarism, and is just more proof, (if any were needed) that the Grifter knows absolutely nothing about the subjects it comments on and has zero credibility.
You can’t get away with these playground antics here Grifter, you’re a fraud.
Btw Grifter, around Norwegian part of the Barents Sea that is Svalbard and it’s pack ice further north, numbers of Polar bears are estimated to have increased by 40% between 2004-2015.
https://www.tandfonline.com/doi/full/10.1080/17518369.2017.1374125?src=recsys
They also conclude: “There is no evidence that the fast reduction of sea-ice habitat in the area has yet led to a reduction in population size.”
“stochastic”
Griff using that word, got me suspicious.
Griff must sit at his computer and constantly refresh the article page so he can be the first one to jump on anything Dr. Crockford posts.
He’s set himself the task of trying to refute anything Dr. Crockford says.
It’s not working, Griff.
Griffin Poo, have you ever heard of evolution? Most species that have lived on earth are extinct. Maybe it’s the polar bear’s time to exit. Or maybe the more fit bears have survived and a rebound in population will leave a group of bears with a better chance of survival. Don’t try to play God.
Griff
Genetic diversity is of course necessary for the genetic health of a population.
However numbers of polar bears are not declining so why would genetic diversity be declining? Perhaps being forced to swim further increases genetic mixing which (paradoxically) would reduce genetic heterogeneity.
In his book ‘World of the Polar Bears’ published in 1989, Fred Bruemmer notes (p118) that
“a bear tagged in 1967 on Spitsbergen was shot a year later in southwest Greenland, more than 2000 miles away.”
I’m guessing the bear didn’t go by ferry.
Great photos in that book!
“In Spitsbergen the open season for shipping at the coal port lengthened from three months in the years before 1920 to to over seven months of the year by the late 1930s. The average total area of the Arctic sea ice seems to have declined by between 10 and 20 per cent over that time.”
H H Lamb Climate, History and the Modern World, 2nd Edition, p260
The polar bears obviously survived that warming and as they have been around for over 100,000 years and gone through many changes in temperature, ice extent etc odds are that they will survive now.
Good on Dr. Susan for calling out political science nonsense masquerading as science. The people that think polar bear diversity is a problem for the future should go hug one and tell them everything is alright (and have someone video the whole event). Thanks.
do I read that world chart correctly ?
temperature trends 1979 to 2018 (approx 4 decades)
with a value of 8.7 deg C per decade
my 10 digit calculator suggests that its warmed around 34 deg C
wow
If there is a problem with genetic make up of that particular population of bears it is actually easily fixed. Pick up a dozen healthy male bears from another region and seed them in that region, same time take a dozen healthy male bears from that region and seed them to others. It ain’t rocket surgery, folks, animal husbandry is quite well understood.
That said, all the pics and video I am seeing of Polar Bears show healthy, apparently happy, bears. How much tax money was pissed away on this hysterical crap?
Er that’s pretty much what the bears do anyway – there is a lot of movement between sub-populations. The hysterical crap and the rather more reasoned response from Dr Crockford both talked about the lack of genetic diversity as a whole species, not the individual sub-populations.
Hey, just trying to help the warmunistas out of their self inflicted dilemma, they clearly are not intelligent enough “think” their way out of it. 😉
There is evidence that bears and other animals do move long distances. The climate wroughters have variously reported losses of 100s of thousands of Adelie penguins, caribou, etc. Only to find them again a few years later several 100s of km away.
Polar bears can swim several hundred km. High ice extent years could also facilitate mixing. This year, a polar bear from the delta of the Yana River in Siberia walked almost across the width of eastern Russia seemingly headed for the Sea of Okhotsk on the south coast near Kamchatka.
He terrorized local villagers who had never seen one before. Wild life officers, picked the bear up and flew him back to the Arctic. (I think Susan Crockford reported on this).
Seals from one herd have been observed to join up with another….
I know, just trying to help out the braindead on the left, they clearly need help.
She was a female bear and got quite a distance before being stopped. As far as I know she was taken to a zoo rather than returned to the Arctic.
Another example of the seemingly endless contrivance of impending CAGW doom.
My thanks to Dr. Crockford for highlighting this occurrence of contrived CAGW doom in the field of mammal biology. She details the authors’ lack of scientific rigor.
Maduna et al. 2021 appears to be founded upon a meme.
Maduna…Mad Una…Mad one (f)
I spent several hours researching this after Dr. Crockford first posted. Most of her non polar bear examples stem from population bottlenecks. The survivors have low genetic diversity, but by definition of the fittest genes, not necessarily bad unless the ecosystem then changes rapidly.
Polar bears are thought to have diverged from browns about 500kya. They have about 25% the genetic diversity of browns. But this is because they have a less diverse environment. There is high polar bear mobility, which offsets the potential ‘inbreeding’ in the various sub populations, as here Svalbard.
more unscientific false climate alarm.
I wonder if, along with the Canadian polar bears I suggested earlier, we could send over some Kodiak and grizzly bears to jump start the genes over in Russia.
Glad you pointed this out.
As the Artic warms the range of other brown bears, part of the same species, merges with the white bears of the polar region. Thus polar bears then have an ample source of genetic diversity brought to them by climate change.
If genetic diversity is a requirement for all species to thrive and adapt, then California sea otters, condors and falcons are already doomed. All research and breeding programs should cease and scarce funds be redirected to other programs with more certain outcomes.
Rhinos, Tasmanian devils, platypus, koala bears, mollusks, owls in the Northwest, sturgeon, whorled pogonia, etc…
That list is very long.
But the question is, how genetic diversity is built up.
To thrive and adapt, species do not necessary depend on pre-existing diversity. Diversity (better said: diversification) is always occurring, it results from gene mutation, recombination, etc., leading to new direct genetic “functions” (so to say) and to epigenic variation. Survival and adaptation to new conditions, either resulting from evironmental “change” or from migration, may be achieved through the selection on very recent “novelties” (i.e., diversity through very recent acquisition of new characteristics). I suppose that modern human evolution can exemplify what I said.
So, loss of diversity may reduce chances of adaptation — or of adaptation through some pathways of evolution. But new diversity can increase the chances of adaptation (eventually, through different patways of evolution).
The question is rather deep, its understanding asks for a lot of knowledge from biology and evolution, it is not a simple and easy matter to be fruitfully discussed by lay people.
I’m also not sure of the timescales involved. Behaviours can change very rapidly, often within a single generation but genetic mutations are over a far longer period and, even then, are little understood. Some researchers believe that genetic mutations occur naturally over many hundreds of thousands of years while others believe that changing circumstances may trigger mutations. Either way, the timescale is likely to be so long that we’re highly unlikely to observe it happening.
Mutations occur. They are not infrequent. But most have no significance in the survival or reproduction of the organism, so we do not “detect” them (except if we are searching for those changes, not an easy task and seldom performed). Circumstances influence the rate of mutation; but we cannot predict what mutations will occur: it is a random process. “Diversity” in Biology is a very slippery thing, especially after thr UN decided to intrude and add “bio-” to the word: everyone talks about it but no one knows actually what he is talking about; the confusion invaded this field of biology and ecology.
In my opinion, what seems to underlie the “fear” of losing diversity results from a very childish idea (though propagated by many television programs and series, e.g., from Discovery and National Geographic, Attenborough, etc.), namely, that “The Genes” are a kind of toolbox, and survival is as much guaranteed as there are many and different tools in that box. Well, maybe, maybe not: a change of conditions demanding adaptation can require a tool that is not to be found in a very well kitted out box; but paradoxically, it may be solved with a Swiss knife… If there is not the appropriate tool, nor the Swiss knife, a species subject to such a change in environment will probably enter the path to extinction. But extintion takes time and, meanwhile, some hopeful mutations, “Swiss knives”, can happen and be diffused in the population…
If you have it at hand, please read the last paragraph of Darwin’s “Origin of Species” (you can find it in many places in the internet): current day biology seems to have forgotten those few lines… “Thus, from the war of nature, from famine and death…”
The critical dogma is diversity of colors that is a utopian vision full of wicked treachery. In the civilized world, it is diversity of individuals, minority of one.
Progressives are fundamentally Collectivists, and have always loathed diversity of thought.
Diversitists assume genetic sensitivity, a uniformity, a simple scalar a la climate sensitivity, that is rarely found in Nature.
We rely on so few brave honest people to fend off the political corruption of science. Susan is essentially on her own in the fight for truth in this particular sector (including polar bears, walruses, seals …).
Ironically, the strongest evidence for lack of diversity in the sphere of climate, is among the the consensus climate scientists themselves. In their case, this, too, was the result of inbreeding, but of the mind.
Susan is on her own, but she puts up the right arguments and evidence.
We know this because Griff complains about it so much.
So trillions of dollars to stop climate change to help the polar bears? How much to charter a boat/expedition to round up some ‘exchange students’ – sending a few Canadian polar bears to Russia in exchange for a few of theirs to mix things up a bit?
Certainly cheaper than global climate poverty.
Y ou would do better to put the money away. There is a lot of movement already between the sub-populations of Polar Bears which is more than enough to mix the genes up a bit. The paper and Dr Crockford talked about a lack of diversity of the whole species, not in the sub-populations.
Genetic diversity is fine when you first start out with a population but if you are trying to fix certain traits, like size, intelligence, easy-gaining, coat and color and so on, pretty soon you end up getting rid of it. Humans do this in their animal breeding programs, nature does this all by itself. We who breed critters call it line-breeding, ignorant souls call it inbreeding. In order to gain and maintain uniformity of type, diversity must be kept low. Both nature and humans cull undesirable specimens.
It oils be nice if the journals publishing articles like this required empirical proof. Consider humans and longevity statistics. Japanese are probably the least diverse population, yet they have the highest life expectancy. Much the same could be said about Scandinavians.
It is Her Choice to select from the fittest of a diversity of individuals, which does not often coincide with her Choice to select from some, select lives that matter in a color spectrum.
Looks like they’ve given up with the emotional walrus thing
They’re rehashing a lot of tired yarns like polar bears are hopelessly doomed and a warmer Arctic means colder winters
Looks like they’re out of ideas
WWF has moved on to spining handmade tales about elephants.
That said, it’s not too late to donate to World Walrus Foundation (WWF), a joint project of walruses and seals. Think of the pups!
I watched a thing on the box the other evening about elephants somewhere in Africa being given contraceptives because there are too many of them in the area.
Planned Pachyderm. Think of the calves!
To be fair, preventing conception is a moral choice, one of four; but, I doubt thst it is her or his choice.
Aaaah, that’s why I can’t find condoms that fit …….
Helena Horton in The Guardian (8th Sept 2021) writes about a paper in the journal Trends in Ecology & Evolution by Sara Ryding of Deakin University, Australia. The paper is about adaptation to climate change, by birds in particular. Something Ryding calls “shapeshifting”
Was interesting until we get to this quote from Ryding
“However, prominent appendages such as ears are predicted to increase, so we might end up with a live-action Dumbo in the not-so-distant future.”
Was she serious or just joking but it passed Helena by?
There hasn’t been a new climate change idea in at least a decade. Their problem is the factual refutations are also at least a decade old. Shriller recycling just make them look foolish. Crockford first debunked the PB genetic diversity scare back in 2015. Newly Recycled to Svalbard only; still wrong.
Should we help the poor darlings out? I’m sure we can think up some scary doomladen headlines for them!
“Increased CO2 in the atmosphere will cause cows farts to become highly explosive!”
Veganism is a GHG multiplier and a first-order forcing of [catastrophic] [anthropogenic] climate cooling… warming… change.
Green Lives Matter
The fittest survive and over time will spawn small genetic differences.
Odds are the narrow view researchers did not analyze deep into the polar bear genetics. Instead taking a snapshot at the higher levels of DNA.
The ancestors of today’s polar bears made it through the previous interglacial period, the Eemian, which was warmer than this one with higher sea levels and more ice cap melting.
Does WUWT earn money from this spammer?
If so, it should be a lot of money.
50% of $100/hour jobs should go to WUWT!
How does a huge increase in numbers of Polar Bears lead to a loss of genetic diversity
It’s because only the conservative bears are breeding.
The liberal ones are too busy protesting to breed.
Typical left wing political thinking, that ALL diversity is always good, anytime, anywhere. Not that anyone is surprised that politics is driving climate science, though
The only two genetic diversity problems I can think of are cheetahs and the Lions in the Ngorogoro crater. Those particular lions certainly do come across as a little ‘special’ and not in the good way. And yes, both of those examples are more to do with bottlenecks
The polar bears will be OK. So long as Coca-Cola is in business, they will have lifetime employment.
It’s true. I saw it on TV.
polar-bear-penguin.thumbnail.jpg (470×500) (wp.com)
Excellent essay. Dr. Crockford’s specialty is evolutionary biology, not polar bears per se. She nails a common myth, that low genetic diversity leads to extinction. Actually, it leads to evolution and is indeed fundamental to Darwinian theory. Survival is a tricky business. A diverse gene pool didn’t save the dinosaurs, but just the right genes did save the birds.
How? I mean really, how would genetics help you adapt to a world in which a million tons of rock falls out of the sky? It would have to work bloody fast!
It wasn’t rocks falling out of the sky. The Chicxulub Event caused a global firestorm and then dozens of years of subfreezing chill from sunlight reflecting impenetrable soot — nuclear winter if you will. Surviving species of all families were small seed eaters with fur or feather coats and/or aquatic or semi-aquatic equatorials. The survivors were warm-blooded with high metabolisms. They probably had advanced visual and auditory capabilities.
Despite all that, it is hypothesized from DNA studies that only a handful of bird lineages survived the KT Boundary catastrophe. A few vulture-like feathered theropods gave rise to the myriad terrestrial bird species of today, in addition to a waterfowl of some sort that gave rise to nearly all aquatic bird species.
Just a few survived, with a limited gene pool, but that was sufficient to engender 18,000 species today and over 200 billion birds.
Polar bears only evolved at the end of the Eemian, a more recent “species” than us humans. They haven’t yet lived through an entire interglacial.
If you need more diversity, add some grizzlies into the breeding mix. They still interbreed.
Humans almost went extinct 70,000 years ago due to Toba.
Look where we are now.
I shouldn’t need to say it, but, I am not “the opposition”.
I’m a very broad centrist who tries to acquire information, facts and opinions from wherever they may be found.
I’m astounded at those who argue for the reasonableness of loss of diversity whose comments seem to be based pincipally on a ‘dislike’ of those who argue otherwise, rather than addressing the available ‘facts’.
I don’t know Griff or his general views but I can easily determine “what camp he is in” by the largely irrelevant comments made by others. It would be hard to fault his first paragraph in general terms. In specific cases outcomes where diversity has been lost may have seemed to have “gone well enough” but we of course do not know with any certainty what otherwise may have happened, and a single example seldom informs us especially well about the general case.
So. <Shields_up>. OF COURSE loss of genetic diversity is liable to have longer term negative consequences in the general case and in most specific cases. Any increase in genetic diversity occurs over utterly vast periods of time by any sensible measure, and any loss is to be regretted. Such loss may indeed lead to a selection process which results is a more robust dominant subset of the original species in a given set of conditions. But it also necessarily elminates other subsets which might otherwise have been “fitter” in other plausible future selection, and longer term does not guarantee what may have been the fitter subset in the longer term will survive.
In situations where “we” have the ability to prevent loss of diversity at ‘acceptable cost’, not doing so is unlikely to be the optimum choice. What constitutes ‘acceptable’ varies widely with context.
When Griff, or anyone else, says somewhat reasonable (or better) things, I suggest that not slanging them just because of who they are and their overall beliefs is liable to be a good option.
<shields [still] up>
🙂
Russell McMahon
rmcspam+diversity@gmail.com