Survival of the fittest. You hear this phrase all the time to sums up Darwin’s theory of natural selection, the way in which species evolve. Individuals of a species that have traits that make them better adapted to their environment have a greater chance to survive and leave more offspring, increasing the chance of that trait among members of the species.

People often think of Darwin’s theory as a heartless, toe-and-nail “kill or be killed” battle to survive but nature is more complex than that. Sometimes the most adaptive thing is kindness, and the best strategy for survival might be to help others.

Altruism may seem counter-intuitive as a survival-of-the-fittest strategy in a fiercely competitive world, but nature has plenty of examples of it. Cooperative or selfless behavior increases survival for a related group. If you think about it a bit, selfish individualism does not always make sense if the goal is survival of your species or for your genes to increase in the gene pool. No matter how fit, all individuals perish eventually. Parents are selfless with their offspring because if the offspring survive, the genes of the parents survive.

Individuals can sacrifice for other related members of their species, increasing the chances for survival rates for other individuals that share many of the same genes, even if they are not their own offspring.

Among insect species, like bees that live in organized colonies, many individuals work for the common good and the survival of the whole community, rather than competing with other individuals in the colony of reproductive ascendancy.

There are even examples of altruistic behavior between species, as outlined in a 1994 study, “The Genetics of Mutual: The evolution of altruism between species.”

A recent study of aphids highlights the pros and cons of altruism as an adaptive strategy, and some of the factors that influence altruism.

The study from researchers at Royal Holloway, University of London, published Feb. 3 in “Proceedings of the Royal Society B,” looked at the social behavior of certain aphid species. The species examined in the study “The impact of colonial mixing on the evolution of social behavior in aphids” include some aphids that cease reproducing and become “soldier” aphids that defend, clean and even mend the communal nest, even at the risk of their own lives. The work of the soldier aphids is essential to maintaining the physical integrity and survival of the nest.

While these individual soldier aphids contribute to the common good, the nest is also colonized by as many as 25% aphids from other colonies. These invaders do not contribute to the running of the colony but do continue to reproduce at the same rate as productive nest members. The researchers looked at whether the altruism of the soldier aphids put them in danger of losing out to the freeloader invaders, as the invaders increased in number and spread throughout the colony.

But one interesting thing they found was that selfless behavior increased when other individuals around them were more likely to also engage in selfless or helping behavior. This similar behavior is described as the “relatedness” of individuals. Increasing the number of unhelpful invaders decreased social cooperation but not enough to lead to a colony collapse. Additionally, the researchers were able to reduce the complex social behavior of the group, including migrations between nests, to a mathematical model that predicted the levels of social behavior. The researchers believe the model can be adapted, with modifications, to predict social behavior in other species.

So even among aphids, it pays to be nice if you want niceness in return, and not even an aphid likes a freeloader.

Cate Marquis is the A&E editor and a columnist for The Current.