In the library of the University of Cambridge, in addition to all the books, maps and manuscripts, there is also a child’s drawing which the curators have called “The Battle of the Fruit and Vegetable Soldiers”.

The drawing shows a turbaned cavalryman facing an English dragoon. It’s a bit crazy: the British soldier is sitting astride a carrot, and the turbaned soldier is riding a bunch of grapes. Both the carrot and the bunch of grapes have horse heads and stick attachments.

It is believed to be the work of Francis Darwin, the seventh child of British naturalist Charles Darwin and his wife Emma, ​​and appears to have been created in 1857, when Frank would have been 10 or 11 years old. And it is drawn on the back of a page of a draft of On the Origin of Species, Darwin’s masterpiece and the foundational text of evolutionary biology. The few leaves of the draft that survive are pages that Darwin gave to his children as drawing paper.

Darwin’s biographers have long recognised that play played an important role in his personal and family life. The Georgian mansion where he and Emma raised their ten children featured a rope swing over the first floor landing and a portable wooden slide that could be placed over the main staircase. The gardens and surrounding countryside served as an open-air laboratory and playground.

Play also plays a role in Darwin’s theory of natural selection. As I explain in my new book, Kingdom of Play: What Ball-Bouncing Octopuses, Belly-Flappers, and Mud-Sliding Elephants Reveal About Life Itself, there are many similarities – so many that if the processes of natural selection could be reduced to a single behavior, that behavior would be play.

No goal, no direction

Natural selection is the process by which organisms best adapted to their environment have a better chance of surviving and thus passing on to their offspring the characteristics that helped them thrive. The process is undirected: in Darwin’s words, “it contains no necessary and universal law of progress or development.”

Unlike foraging and hunting – behaviors with clearly defined goals – play is also undirected. When a pony frolics in a meadow, a dog wrestles with a stick, or chimpanzees chase each other, they act without a goal.

Natural selection is entirely provisional: the evolution of any organism responds to the conditions prevailing in a particular place and at a particular time. Animals at play are also provisional. They constantly adapt their movements to changing circumstances. Playing squirrels change their tactics and routes when faced with obstacles such as falling branches or other squirrels.

Natural selection has no end. Life forms are not fixed but are constantly evolving. Play also has no end. Animals start a play session without planning when they will end it. For example, two dogs that are playfully fighting will not stop playing until one of them is injured, exhausted or simply loses interest.

Natural selection is also wasteful, as Darwin admitted. “Many more individuals of any species are born than can survive,” he wrote. But in the long run, he acknowledged, such wastefulness can produce adaptations that allow an evolutionary line to become “fitter.”

Play is also wasteful. It requires animals to expend time and energy that could perhaps be better spent on survival-critical behaviors such as foraging and hunting.

And this extravagance has its advantages. Animals forage and hunt in certain ways that don’t usually change. But a playful animal is much more likely to innovate – and some of its innovations can be converted over time into new ways of foraging and hunting.

Compete and cooperate

Darwin initially framed the “struggle for life” as being largely a competition. But in the 1860s, Russian naturalist Pyotr Kropotkin concluded from observations of birds and fallow deer that many species were “most numerous and most prosperous” because natural selection also favored cooperation.

Scientists confirmed Kroptokin’s hypothesis in the 20th century and discovered all kinds of cooperation, not only between members of the same species, but also between members of different species. Clownfish, for example, are immune to anemone stings. They nest in the anemone’s tentacles for protection and in return keep the anemones free of parasites, provide them with nutrients and drive away predators.

Play involves both competition and cooperation. Two dogs that are playfully fighting are competing with each other, but to maintain their play they must work together. They often switch roles: a dog that is in a better position may suddenly give up that advantage and roll onto his back. If one of them bites harder than intended, he will likely back away and do a play bow – essentially saying, “My bad. I hope we can keep playing.”

Both natural selection and play can involve deception. From butterflies that are colored to resemble poisonous species to wild cats that squeal like distressed baby monkeys, many organisms use mimicry to deceive their prey, predators, and rivals. Animals can also learn and practice deception during play—particularly play fighting.

Life is about playing

Darwin wrote that natural selection produces “innumerable forms of the most beautiful and wonderful.” Play also creates beauty in countless ways, from the aerial acrobatics of birds of prey to the sweeping, twisting leaps of dolphins.

In 1973, Ukrainian-American geneticist Theodosius Dobzhansky published a paper with the blunt title “Nothing in Biology Makes Sense Except in the Light of Evolution.” Many biologists would agree. Perhaps the most satisfying definition of life is not concerned with what it is, but with what it does – that is, life is that which evolves through natural selection.

And since natural selection has so much in common with play, we can reasonably say that life is playful in the most basic sense.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

David Toomey is a professor of English at UMass Amherst.