Climate Change May Make Humans Shrink in Size to be Able to Adapt to Rising Temperatures

Prof Steve Brusatte, a palaeontologist at the University of Edinburgh, noted in his book “The Rise and Reign of the Mammals,” that today’s animals living in warmer parts of the planet are often smaller than those in colder regions.

The principle is called the Bergmann’s Rule in zoology. According to Carl Bergmann, a 19th-century German biologist, who proposed it, there is a correlation between external temperature and the ratio of body surface to weight in warm-blooded animals like birds. It is an adaptive mechanism in order to radiate or conserve body heat, which depends on climate.

“The reasons are not entirely understood, but it is probably, in part, because smaller animals have a higher surface area relative to their volume than plumper animals and can thus better shed excess heat,” wrote Brusatte.

In an interview with the Guardian before the publication of his book, Brusatte explained that shrinking in size is “a common way that mammals deal with climate change”.

He further expounded that not every species of mammal would shrink in size, but it appears to be a common survival trick among mammals when temperatures rise rapidly. A matter that raises the question: if temperatures do spike really quickly, might humans dwarf, might humans get smaller? In answer to it, Brusatte said it was plausible.

As an example, Brusatte mentioned the so-called hobbit humans, Homo floresiensis, who once inhabited the Indonesian island of Flores. They shrunk due to scarce resources.

Brusatte’s argument was supported by authors of a recent study on millions-year-old human remains, who likewise expressed that temperature is a major predictor of body size variation as published in Nature.

However, there are other experts who disagree with Brusatte like Prof. Adrian Lister of the Natural History Museum in London who said that the recent human remains study offered weak evidence for its claim and that the strong correlations between temperature and a mamalian body size may often be attributed to the availability of food and resources.

Lister also doubts that humans will shrink as global temperatures rise. “We are not really controlled by natural selection. If that was going to happen, you’d need to find large people dying before they could reproduce because of climate warming. That is not happening in today’s world. We wear clothes, we have got heating, we have got air conditioning if it is too hot.”

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