How did the elephant get its trunk? The leopard, its spots? The camel, its hump? We think scientists agree on the answers to these just-so storiesThree stories from Rudyard Kipling's 1902 book Just So Stories for Little Children. The phrase "just-so stories" is now used to describe explanations that lack sufficient evidence.: millions of years of the natural selection of genes, traits and species. The theory of evolution.

But what about the Senegal bichir? A fish with gills and lungs. When scientists raise them on land, they grow long sharp fins to pull themselves along. In one generation, they make the tiny steps our ancestors evolved over millennia.

This is called plasticity. A form of adaptation seen in many species, including dung beetlesWhen moved to a colder climate, these insects grow larger wings to help them fly. and spadefoot toadsA tadpole fed solely on meat grows more powerful teeth and a tougher gut.. It is just one example of how new research casts doubt on the story of life. Now, a rebel alliance of biologists have declared war on the theory of evolution.

In 1859, Charles DarwinHis book, On the Origin of Species by Means of Natural Selection, is the founding work of evolutionary biology. published his big idea to explain the astonishing diversity of life on Earth. Every island, hill and forest is home to species perfectly adapted to their environment. Across 3.7 billion years, natural selection picked out the winners and let over 5 billion species go extinct.

The discovery of genesThe behaviour of genes was first observed by Gregor Mendel (1822 - 1884) in his experiments with pea plants. Modern genetics developed in the 20th Century. helped explain this process. But it also revealed other factors at work: inheritanceThe rules that determine how characteristics, like eye colour, are passed from parents to children., random chance and mutationChanges caused by errors in gene copying.. Still, most biologists argue natural selection is the most important force shaping life. Until now.

Some researchers think we have ignored the role of culture in evolution - how dolphins pass on hunting techniques or birds learn a distinct dialect. Other scientists believe an illness or injury can affect DNA. They use this theory of epigenetics to understand stress in the children of Holocaust survivors.

The traditional theory of evolution struggles to explain how the first eye or wing appeared, says biologist Armin Moczek. "This classic idea of gradual change, one happy accident at a time, has so far fallen flat." He supports the new Extended Evolutionary SynthesisThe Modern Synthesis merges the theory of natural selection with genetics. The EES aims to extend this framework to include the latest research on evolution..

"Strange." "Irritating." "Disgraceful." Some of the words biologists are using to describe this idea. Jerry Coyne accuses its supporters of being "revolutionaries" only to advance their careers.

"We're not here to explain the elephant's trunk or the camel's hump," says Brian Charlesworth. There will always be exceptions and surprises, but a grand theory must consider all living things. And the universal force in biology is still natural selection.

Darwin did not coin the phrase "survival of the fittestA term made famous by Charles Darwin, suggesting that individuals or species best adapted to their environment are the most likely to survive and reproduce. ", but we often use it to explain his theory. It does not mean the strongest, meanest and most selfish creatures triumph. "Fitness is just your ability to reproduce," says science writer Vanessa Woods. And sometimes, you need to cooperate to survive.

So the new wave of scientists are working together to take down the ruling order of biology. In their Extended Evolutionary Synthesis, natural selection will be one of many evolutionary forces. And biologists will build a new theory of life.

Traditionalists warn they threaten the future of biology as a science. But radicals say this is a war and they will win.

Yes: The traditional theory is an old fossil. Biologists no longer find it helpful to explain their research or to communicate with each other. It harms scientific cooperation and the future of knowledge.

No: Scientists constantly improve how we understand evolution, so there is no need to reinvent the wheel. It would be unscientific to scrap the theory of natural selection without sufficient evidence.

Or... Do we even need a theory of evolution? These big projects to unify biology are old-fashioned. Biology does not need to be like physics or chemistry in order to do good science.