Mary Dejevsky: The future is warmer – and smaller

Survival, it seems, is no longer about being bigger. Hooray!

As someone used to being described, like John Bercow, the new Commons Speaker, as "diminutive", or – its more flattering female equivalent, "petite" – I have long been sceptical of the assumption that bigger and taller are necessarily better. At school, I might have been among the last to be selected for netball teams, but I was also one of the last to be voted out of the hypothetical air balloon in end-of-term classroom games, when smaller, lighter, more inventive were the qualities in demand.

This is probably why I took particular pleasure from recent science reports about sheep on the remote Scottish isle of Hirta, somewhere even outer than the Outer Hebrides. Over the past 20 years, biologists have found, these sheep have been getting smaller – the reverse of the trend observed in most animals. Daughters, it seems, are now lighter on average than their mothers at the same age, and their legs are shorter. This trend presented an especial puzzle, given that animals living in freezing climates tend to evolve into bigger, heavier creatures, the better to withstand the cold.

In search of an explanation, the biologists, from Imperial College, London, alighted on climate change. And – once you get over the knee-jerk response that they would, wouldn't they, given the amount of research money pouring into climate change and the way it has come to dominate scientific discussion these days – you can appreciate the logic.

If the temperatures are getting warmer, the summers longer and the winters shorter, the sheep do not need to be bigger or fatter to survive. And it follows from this that, if greater numbers live past the first few months, there may also be more competition for food. So, on the one hand, they do not get as much, and, on the other, they do not need as much. Survival is no longer about being bigger, but about being smaller. Hooray!

It is also, of course, about adaptation. Which is why I was doubly distressed by the generally negative gloss put on these research findings. The underlying assumption has been not only that small is always inferior to big, but that the effect of climate change is bound to be destructive. I cannot for the life of me understand why it should be unscientific to look, for once, on the bright side.

Rather than lamenting the shrinking of the Hirta sheep, perhaps humankind should be rejoicing. If – and the scientists seem quite tentative in their conclusions – climate change is playing a role here, could this primitive breed be starting to exemplify an alternative to catastrophe?

If these sheep are adapting to warmer temperatures, why exclude the possibility that humans can, too? It might entail population shifts or changes in agricultural practices; it might mean we progressively reduce our consumption. And why does it have to be painful? We are talking evolution here, not revolution.

Maybe, like the Hirta sheep, future generations will also become smaller, more compact, less ecologically demanding. That would be cheering news for the likes of John Bercow and me; excellent news, too, for the planet. Small might not necessarily be beautiful again, but it could be the size of the future.