Many people like to exclaim that being alive is mainly about competition of one kind or another. For all living things, they say, survival is a contest. And in the 19th century, for those making their way in the capitalist economies of Europe and America, competition certainly seemed fundamental. So when Darwin published On the Origin of Species in 1859, he added the stamp of science to this oppositional view of existence.

Cooperation, by comparison, has a much weaker foothold with the public as a fundamental feature of being alive. Our countless daily cooperations among family and colleagues unremarkable to most people. In the late 1800s, while Social Darwinists promoted Darwin’s work as a justification for capitalist exploitation, research on mutual biological interactions was scorned as subversively Marxist and ignored. Today, competition—political, economic, athletic, social—makes headlines while successful social collaborations make the human interest pages.

Mutualistic symbiosis, the term that biologists use for cooperation, refers to close interactions that benefit both parties. They are a “win-win”; competitions are “win-lose.” In their many forms, mutually beneficial interactions pervade the living world and play every bit as crucial a role in its continuity as Darwinian competition. Here is a scan of such relationships, ranging from human cooperation, through mutual assistance between members of different species, down to the integration of one organism into another.

1. We humans are genetically wired to connect with other people whenever we think we can do so safely. And when we’re not actually engaging with others, we’re almost always thinking about doing so. Some of that thinking is competitive of course, but much of it is cooperative.
2. Many other animals are also intensely social and cooperative, from ants and bees to rats, starlings, gorillas, killer whales, and vampire bats.
3. Mutualistic interactions take place not only between members of the same species but also between members of very different species. Different kinds of living things that live near each other often exchange regular and vital assistance in some form. Bees fertilize flowers and find food in return.
4. 

   Hermit crab and anemone, protection in exchange for food
   (wonderopolis.org)

   Such interactions between different species can amount to full-time or almost full-time partnerships. Humans keep cats and dogs, and they keep us, for the steady mutual benefits. More exotic are the hermit crabs that carry a pink anemone on top of the shell that the crab has housed itself in. The anemone’s poison darts keep predatory fish away from the crab and the crab’s meal leftovers feed the anemone. When the growing crab moves to a larger shell, it even brings its personal anemone with it.

5. Sometimes such mutually beneficial relationships take place with one organism inside the other. Consider the three or four pounds of bacteria inside your body that gain a home while digesting your food.
6. Helpful sharing takes place even at the cellular level. Cells can actually give a copy of their genetic material to the cell next door. A notorious example are bacteria that are immune to antibiotics. One way bacteria acquire such resistance is that a resistant bacterium transfers a copy of its genes to an adjacent, non-resistant bacterium. Bad for us, good for the bacteria.
7. Finally and most profoundly, certain components of the ordinary cell, the building block of life, turn out to be the descendants of independent bacteria that long ago were absorbed into other bacteria where they continued to pursue their specialized functions. Two such cell components are chloroplasts, which carry out photosynthesis, and mitochondria, which process oxygen to create energy. Around two billion years ago, these were free-floating bacteria. Some of them were “swallowed” by simpler bacteria. Today they provide the photosynthesis in plant cells and the energy of animal cells. In exchange, they enjoy a protected environment. Evolution might well have stalled without these mergers.

We living things are cooperative ventures at every level, in addition to being fierce competitors. Cooperation and competition are our yin and yang, complementary forces that constrain and generate each other, whose result—thriving life—seems much more than the sum of the parts.

A useful source on mutualistic symbiosis and the ongoing debate about its place in evolutionary theory is Darwin’s Blind Spot: The Role of Living Interactions in Evolution by Frank Ryan.