‘Pizzly bears’, genes and the climate crisis

Grizzly/Polar: The pizzly has evolved to survive rising Arctic temperatures. © Getty

Will evolution help defeat climate change? Yesterday, Joe Biden launched a “decisive decade” of environmental action. Now it seems that nature might also offer a helping hand.

In 2006, hunters in the Canadian Arctic spotted a polar bear unlike any they had seen before. Its white fur was mixed with brown patches, while its long claws and humped back resembled those of the grizzly bear.

DNA tests discovered that it was nature’s first known pizzly bear: a hybrid of polars and grizzlies. Several others have since been sighted.

Yesterday, to mark Earth Day, US President Joe Biden invited 40 world leaders to discuss climate change ahead of COP26. The discovery of the pizzly suggests that nature might be ahead of him.

Recent research by palaeontologist Larisa DeSantis suggests that the pizzly bear has emerged in response to global warming.

Polar bears evolved thousands of years ago. Their teeth specialise in eating soft seal blubber. But the melting Arctic ice cap has made hunting seals much harder, forcing them to move south to find other food.

Warmer forests have pushed grizzlies further north. By mating with grizzlies, polars create offspring able to eat a more varied diet. DeSantis says: “Time will tell if these hybrids are better able to withstand a warming Arctic.”

Hybridisation is a common part of evolution. Since the 1940s, North America has been home to coywolves, fusions of wolves and coyotes optimised to hunt deer.

The Heliconius butterfly of the Amazon, meanwhile, owes its vivid colours to crossbreeding. This has an evolutionary advantage: the patterns alert would-be predators to the cyanide inside the butterfly’s body.

Climate change has accelerated shifts in nature. Researchers in Canada have observed squirrels giving birth earlier in the year, allowing their offspring to benefit from the warmer spring.

Perhaps humans will also evolve to face the times. We could develop sun-resistant skin, a reduced need for water or stronger lungs to filter air pollution. Scientists believe that our ears evolved from gills. If the world floods, perhaps we could regain them.

The Gaia Paradigm, suggested by the chemist James Lovelock in the 1970s, contends that all things on Earth work together to ensure the survival of life. Many view this theory with scepticism. Scientist Toby Tyrell calls it a “dead end.” But on a smaller scale, evolution might be lending a hand.

Few would claim that evolution alone can stop the climate crisis. Issues such as deforestation and waste dumping will remain even if we adapt to higher sea levels.

And evolution is often a gradual process: 5.6 million years separate the appearance of our oldest human ancestor and the modern homo sapiens.

Climate change is very different. “The most terrifying thing about climate change,” writes novelist Jonathan Franzen, “is the speed at which it is advancing.” Journalist David Wallace-Wells estimates 30 years until irreversible catastrophe, while ecologist Stuart Pimm claims that humans are driving animals to extinction at 1,000 times the natural rate.

Will evolution help defeat climate change?

Bare necessities

Hopefully, say some. New hybrids indicate that organisms are able to adapt to climate change. Evolution helped life survive the Palaeocene Eocene Thermal Maximum, the prehistoric world’s closest analogue to contemporary climate change, and it could help again. It can also encourage more action: the very existence of the pizzly bear should help people take notice of our growing crisis.

Unlikely, say others. Evolution offers resistance to climate change, but does not help defeat it. It happens in response to circumstances. But it is likely that the conditions created by global warming will be too extreme and too sudden for evolution to react to. Besides, the environmental crisis is entirely driven by human activity. Only a dramatic shift in our behaviour can stop it for good.

You Decide

  1. Does it matter if the polar bear goes extinct?
  2. If humans evolved gills to breathe underwater, would we remain humans?

Activities

  1. Working in pairs, conceive and draw a hybrid animal. Present it to the class, explaining the conditions that caused it to evolve and the benefits of its evolution.
  2. In groups, research the specific issues affecting a country. Imagining you are that country’s delegation at Biden’s summit, deliver a presentation to the class explaining the problems and the required solutions.

Some People Say...

“Man selects only for his own good: Nature only for that of the being which she tends.”

Charles Darwin (1809 — 1882), British naturalist and pioneering evolutionarily theorist

What do you think?

Q & A

What do we know?
It is generally agreed that cross-breeding – known to scientists as genetic exchange – is a common feature of natural history. Research has found that modern humans carry Neanderthal DNA, suggesting that we ourselves are a 60,000 year old hybrid. Climate change has often augmented this process, with several new hybrids identified in recent years. Geneticist Michael Arnold says: “Genetic exchange due to organisms coming together from climate change is the rule rather than the exception.”
What do we not know?
There remain significant questions over whether hybrids will actually help their species to survive climate change. For one, hybrid animals are largely unprotected by law from human activity. Some examples are weaker: a study by the US Geological Survey has found that a new hybrid of cutthroat and rainbow trout is “less fit” to survive than the native cutthroat population. And they may be unable to reproduce – the vast majority of mules are infertile, for example.

Word Watch

Pizzly bear
A portmanteau of polar and grizzly. Other hybrids include, ligers, zonkeys, geeps, wholpins and beefalos.
Hybrid
The offspring of two plants or animals of a different species. It comes from the Latin hybrida, which referred to the offspring of a tame pig and wild boar.
Earth Day
An annual event on the 22 April in support of environmental protection. It was first held in the US in 1970 and consisted of protests.
COP26
The UN Climate Change Conference, to be held in Glasgow this November. The summit aims to set new environmental targets.
Palaeontologist
A scientist who studies prehistoric life. Prior to her work on pizzly bears, DeSantis studied saber-tooth cats.
Evolved
Charles Darwin only used the word evolution once, in the final paragraph of The Origin of Species.
Arctic ice cap
Over the past 30 years, the Arctic has warmed up at about twice the rate as the rest of the globe.
Cyanide
A toxic chemical compound often used in mining to dissolve gold and silver.
Gaia Paradigm
Lovelock named his idea after the Ancient Greek personification of the Earth.
Scepticism
A questioning or doubting attitude. The Skeptics were Ancient Greek philosophers who believed there were limits to human knowledge.

Subjects

PDF Download

Please click on "Print view" at the top of the page to see a print friendly version of the article.