Interview by Grégoire Canlorbe
Susan Janet Crockford is a Canadian zoologist, author, and blogger specializing in Holocene mammals. From 2004 to 2019 she was an adjunct professor in Anthropology at the University of Victoria. She is best known for her blog posts on polar bear biology, which oppose the scientific consensus that polar bears are threatened by ongoing climate change. In October 2019 she was interviewed by Grégoire Canlorbe—on behalf of the Association des climato-réalistes, the only climate-realist organization in France. The English version of the conversation was first published on Friends of Science, in December 2019.
Susan J. Crockford: I live in Victoria, British Columbia, and I specialize in animals from the late Pleistocene, so probably the last fifteen to twenty thousand years. I have a contract company called Pacific Identifications Inc. We identify animal bones from archaeological projects and also from biological research: stomach contents, fecal samples, that kind of thing. That’s primarily how I get my income. And then, I am also a former adjunct professor at the university—I had held that position since 2004 but in 2019, it was not renewed.
My primary interest—my overall interest—is evolution. That, for me, really informs everything. It’s the big picture. Evolution is the big idea that drives all my interest. For example, the interesting thing is that a deer bone from 8000 years ago looks like one living today, and so, there is continuity. But there are also distinctions—when you get species differences, those are apparent. I became interested in polar bears when I was working on the topic leading up to my PhD dissertation. I was looking at the speciation process that turns a wolf into a dog (what we also call domestication). While trying to unravel what biological process drives that transformation, the wild species that I looked at to compare it to was the brown bear to polar bear transformation. So, I’ve been looking at the literature on polar bears (their life history, their ecology, and the geological history of sea ice) since the 1990s. I’ve been investigating polar bears for quite a while.
Grégoire Canlorbe: Your most decisive feat of arms in evolutionary biology may be your claim that thyroid rhythms alone are responsible for all significant differences in life history traits. Could you remind us of the outlines of your approach?
Susan J. Crockford: I don’t actually claim that thyroid rhythms alone drive evolution, although I suspect it may be the dominant driver in many cases. What really drives evolution is individual variation. So, within a species, animals are all different in some critical ways. And the primary hypothesis that most biologists go by is that those individual differences are primarily genetic: that genes are what controls those critical differences, and, therefore, genes, or genetic change, is what drives speciation change in evolution.
But my concept looks at the idea that because thyroid hormone is so important for so many different but inter-related biological processes—like fetal development, brain development, growth, behavior—those individual differences within a species also include thyroid hormone metabolism. All hormones are produced in a rhythmic fashion: they are released in pulses that differ in strength and frequency over the course of a day. It’s similar to a song for a particular bird species. They sing virtually the same song within a species, but if you look at that species’ song closely you find that each individual bird sings slightly differently. So, the hypothesis is that an individual within a species has an individual thyroid hormone rhythm that’s unique to that individual but overall typical for its species, and that this unique thyroid hormone rhythm strongly affects its behavior, particularly in growth and response to stress. A speciation event (one species transforming into another) often involves the colonization of a new habitat, a new ecological niche. When that happens, I propose that only animals with a particular stress response (governed by its unique thyroid hormone rhythm) choose to occupy that niche.
So, if we’re talking about a polar bear transforming from a brown bear ancestor, I suggest that a few brown bears decided at some point during a major glacial period that life would be better for them if they moved out onto the sea ice where seals lived and gave birth to pups. They learned how to hunt seals, but only the individual animals who were extraordinarily curious and not fearful of the new habitat moved onto the sea ice. And when they started to interbreed amongst themselves on the ice, they quickly created a new subpopulation that was physiologically different from the others that stayed on land. Over time, within just a few generations, that would have created a new set of physiological differences within those ice-living bears that made them different from the original population.
It’s a bit complicated to explain, but one of the things that thyroid hormone does is affect how genes function. So, what I’m proposing is that rather than only genetic changes and genes themselves driving evolution, that you can also have changes in these hormone rhythms that control how genes function. And that provides a mechanism for how evolution can proceed quickly, especially in response to changing climatic conditions. My book on this topic is called Rhythms of Life: Thyroid Hormone and the Origin of Species.
Susan J. Crockford with Grégoire Canlorbe — Paris, October 2019
Grégoire Canlorbe: As a well-known debunker of the spread of disinformation on polar bears, what are the main objective facts of which you would like to remind us? How do you explain this religious cult surrounding the theory of an anthropogenic global warming with catastrophic consequences for the planet?
Susan J. Crockford: Around the year 2000, it seemed that the polar bear was elevated to a position as icon of global warming because the Arctic amplification effect proposed that the Arctic and the Antarctic would actually warm much faster than the rest of the world. And as a consequence, it was proposed that polar bears would be affected first and more strongly than any other animal. And it was proposed that polar bears would then be the canary in the coalmine for global warming, and that the inevitable catastrophe that would affect polar bears would eventually happen to us. And a few years after that, the biologists who were working on polar bears sort of took up that idea and formally proposed that it was very likely the polar bear populations would decline dramatically if the sea ice in summer declined dramatically. And when the summer ice dropped suddenly in 2007, it became more and more of a hysterical response.
It is true that we’ve fallen into a trap, looking at some of these things in a very confined way to the extent that it begins to look like religious thinking, rather than scientific thinking. I think what was disturbing and unscientific was a desire to have a statement about consensus. And I saw this myself in evolutionary thinking because what happened at the time was that there were creationists who were fighting very hard, especially in the US, against evolutionary biologists. And so, to counter that difficulty, their strategy was to create a consensus statement: something like ‘this is what we believe about how evolution works’. And I felt at the time that was very wrong but shortly afterwards, the same thing happened with global warming: rather than deal with the legitimate questions and concerns that some scientists were raising, what they did to protect themselves was issue a consensus statement. And so, the consensus statement is what makes this look like religion. Science should thrive on challenges such as these, not hide from them.
Grégoire Canlorbe: It has been hypothesized that the alleged decrease in the extent of pack ice, far from being detrimental to polar bears, is actually allowing for a warmer ocean—and therefore a more hospitable ecosystem for polar bears. Did your researches lead you to endorse that view?
Susan J. Crockford: Yes, to a degree that’s true, especially for summer ice. What was proposed around 2005-2006 was that when summer sea ice declined, polar bear numbers would decline. That the bears required ice in summer in order for them to find food. And they then proposed that if it got to be so there was no ice in summer, the bears would be nearly extinct. However, I was immediately suspicious of that prediction because we know that the bears survived at least two or three warm interglacial periods that were warmer than today and that had little to no ice in the summer. We don’t know exactly how the bears responded to those conditions—whether the population may have declined by half or not—but enough survived to be an abundant species in the Arctic 200 years ago.
But what has happened is that the ice declined in 2007 to a level that the sea ice experts said would not happen until 2050. So, the ice declined several decades before it was expected and has stayed down at that level ever since (with some wide swings year to year). Biologists have continued to collect data in the field, studying bears, and what they’ve discovered is that, in some areas, the bears are in better shape with less ice in summer than they were with more ice in summer. And they’re finding that the seals which the bears eat—ringed and bearded seals—actually do much better with less ice in summer because that’s when they do most of their feeding. Also when they’ve been doing surveys to count the bears in areas that either have had no counts before, or have only one that was done long ago, they’ve discovered that instead of declining in number, they have either remained stable or increased in abundance.
So, the long and short of it is that the prediction that the bear numbers would decline by two thirds failed. Not only did the bears not decline, but the global population number rose by at least 16 percent, perhaps more. What I have done is look at the literature, and summarized the data to draw this conclusion. It means that polar bears have flexible strategies for dealing with less summer ice, which is what you would expect from a species that has survived previous warm periods.
Polar bear — Zoo de la Flèche
Grégoire Canlorbe: It seems that the colder winters encountered in Europe and Asia (with respect to those existing in Africa) have led natural selection to play in favor of high intelligence—and high K strategy—in Europeans and a fortiori East-Asians. Is such hypothesis plausible also in the case of polar bears and other artic species?
Susan J. Crockford: This K selection theory is one of the hypotheses that has gotten polar bear biologists into trouble because it’s a notion that was proposed in the 50s and 60s that most modern biologists have dismissed as not being helpful. What it says is that the Arctic environment should be stable all the time. But what we actually know from geological and recent history is that it’s not stable: ice extent and thickness goes up and down in cyclical fashion. In fact, both the bears and the seals they depend on for food are actually adapted to a very dynamic, ever-changing system rather than a stable system.
I think that this is really the critical driving force for their evolution: they need to be adaptable and flexible in the short term and the long term. Flexibility is what allows them to survive in the Arctic. I don’t think that really answers your question, but I really do think that what goes on in the Arctic is the opposite of K selection theory. The Arctic isn’t stable, it’s dynamic.
Grégoire Canlorbe: You have studied at length the domestication and speciation processes. How do you sum up the evolutionary pressures which led the polar bear to emerge as a wild species, while dogs were designed as domestic animals? Do you think that those lovely companions have a soul like humans allegedly do?
Susan J. Crockford: The domestication and speciation processes, I think, are essentially one and the same. We’re encouraged to think of domestication as something that humans did actively, that they actively participated in creating a new species that’s a dog, or a pig, or whatever. But my theory proposes that, in fact, what humans did was create a new habitat. The first human villages were habitats that hadn’t existed before, and that attracted some wolves to it that, then, ended up becoming dogs. But actually, humans probably couldn’t have stopped this from happening, even if they’d wanted to. In other words, the transformation of some wolves to dogs was a natural response from the animal community to the humans creating this new habitat. And so, then, when you look at brown bears to polar bears, it becomes the same system: some individuals from the brown bear species invading a new habitat for them, which was the sea ice habitat. And then, they emerged as a new species. There are other parallels.
For example, brown bears and polar bears can breed together, the same as dogs and wolves can. Genetically, they’re very close. And also, in terms of behavior between the two, polar bears are less dominant than brown bears. So, if brown bears and polar bears come together in the wild—there are a few places where this can happen, such as the north slope of Alaska at one of the piles of whale bones that have been left behind by hunters—when this happens you see that small grizzly bear (aka brown bear) females chase away big male polar bears. Her behavior is much more ferocious, and the big male is afraid of her. The same with a wolf and a dog. A wolf’s behavior is much more aggressive than a dog’s so a small female wolf easily intimidates a big male dog.
Now, you wanted to know about dogs having a soul comparable to humans. And I think that’s something people have imagined because they would like it to be true. Dogs have had to adapt their social structure in order to fit in with human life and some of what we see is part of that adaptation. And that, over the last 200 years, that’s become increasingly the case. For example, urban dogs are much more dependent on people than they ever were, say, 100 years ago. Modern urban dogs are much more dependent on people than modern dogs that live on farms.
In short, I don’t think that dogs have a soul. I don’t even think people have a soul.
French TV show Bonne nuit les petits [Good night children]