The power of petite

Discovery

BBC

Science, Technology

4.3 • 1.2K Ratings

🗓️ 9 September 2019

⏱️ 26 minutes

🔗️ Recording | iTunes | RSS

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Summary

Bigger is better, right? An ancient lore in biology, Cope's rule, states that animals have a tendency to get bigger as they evolve. Evolution has cranked out some absolutely huge animals. But most of these giants are long gone. And those that remain are amongst the most threatened with extinction. Scientists now believe that while evolution favours larger creatures, extinction seems to favour the small. If you look at mammals, at the time of the dinosaurs, they were confined to rodent-sized scavengers living on the periphery. But 66 million years ago, the dinosaurs went and allowed the mammals to evolve into some really big creatures - 30 metre long blue whales, the ten tonne steppe mammoth and a giant ground sloth that looked a bit like a hamster but was the size of an elephant with enormous hooks for hands. Now, only the blue whale remains and these have been shown to have shrunk to half the size of their Pleistocene ancestors. So is it better to be small? Smaller animals need fewer resources and smaller territories. With the planet in such peril - are more animals going to start shrinking? Well, perhaps...new research shows that in 200 years' time, the largest mammal might be the domestic cow. And of course the most successful organisms, in terms of biomass, on the planet are the smallest. Zoologist, Lucy Cooke examines the science of being small, and why size matters. Producer: Fiona Roberts (Photo: Honeybee sitting on a flower. Credit: Dr Paul F Donald)

Transcript

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0:00.0	Hello, I'm Lucy Cook, and I'm on the hunt for something rather special.
0:08.0	Something rather small. Oh my word that is so well camouflaged. That is a pygmy sloth sitting chilling in a tree. My word, it's so tiny.
0:30.0	The peculiar pint-sized pygmy sloths are a dwarf species that can only be found on one
0:38.2	tiny island off the coast of Panama. It broke off from the mainland some 9,000 years ago and ever since then the sloths have been
0:47.2	shrinking. But why? In this discovery on the BBC I want to investigate the advantages of being small
0:56.2	and find out why animals are the size they are.
1:00.3	Being small means that you can get to your breeding age much faster.
1:04.0	It means that you can have more offspring in less time.
1:07.0	In a lot of spiders, the male is very small compared to the female.
1:11.0	But if he's a bit smaller, he might be less likely to be nabs when they're mating.
1:17.0	You're more agile, you're fast, and if you want to fly, you have to be small, because it's really hard to be a big-volent animal.
1:27.0	Sounds pretty convincing to me, but to fully understand why it pays to be petite,
1:35.4	we first need some of the basics.
1:37.3	The size an animal is, really does all boil down to energy, so it's trade-offs between obtaining energy and then transforming it
1:45.2	into either metabolism or new babies.
1:47.9	This is Felicia Smith, paleontologist at the University of New Mexico. She has dedicated her life to trying to answer the question of why animals are the size they are.
1:58.0	Evolution is all about maximizing your ability to gain energy.
2:02.0	And at different times in evolutionary history, depending on the
2:04.9	environment, depending on the other predators and competitors are present, you might expect a different
2:10.7	optimal body size, right?
2:12.5	Energy, it makes sense.
2:14.5	You are what you eat.
	...

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