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Kin Selection: Definition, Theory & Examples

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Adrienne Brundage

Kin selection is a type of natural selection in which an individual attempts to ensure the survival of its own genes by protecting closely related individuals first.

Definition

Kin selection is a type of natural selection. Individuals will sacrifice their own lives in an effort to save closely related organisms, therefore ensuring the survival of genes that they both share.

Family First

Ah, family. It's a complicated, thing, isn't it? One day you're arguing over the remote, the next you're coming together for a big dinner, and then you get to fight over who does the dishes. But what happens if someone decides to pick on your little brother? Or gossips about your sister? Or, horror of horrors, insults your mother? There is nothing that that makes someone angrier than when a family member is attacked in some way. Why is that? Why can we get so frustrated with our own relatives, yet get so angry when someone outside attacks them? Enter kin selection.

Genes Want To Be Passed On

You share a lot of things with your family, but at the most basic level, you share genes. Every individual inherits his or her genetic code from his or her parents. This is true for all living things, no matter how they pass their genes on. This also means that every living thing has genes in common with its parents, its siblings, and its offspring. Have you ever noticed that you look a lot like a beloved aunt? Or your brother is the spitting image of your grandfather? Those are common genes that you all share.

Now, the whole purpose of reproduction is to pass genes on to the next generation. Scientists call this the biological imperative, or the biological drive for every living thing to reproduce and pass on genes. But have you noticed that not every single living thing on earth has the ability to pass on its genes? I'm sure you've met people who can't have children, but did you know that there are animals that have lost reproductive ability completely?

Honeybees, for example, are mostly all female, and are mostly all infertile. They live in hives with a single queen that produces eggs, while hundreds of worker bees take care of everything else. If the whole purpose of life is to pass on genes, why are worker bees willing to take care of another bee's baby? Because the worker bees and the baby bees share a mother, which means they are all related, and share the same genes. So, by caring for the new babies, the worker bees are making sure that those genes they share are going to be passed on to a new generation, without having to have offspring themselves. This caring for closely related individuals at the expense of personal fertility is known as kin selection.

Altruism in Action

Kin selection is a type of altruistic behavior. Altruistic behavior is a set of actions by an an individual that benefits someone else, while often causing harm to the individual. This is a form of selflessness that helps others survive and reproduce.

For a long time, altruistic behavior didn't make sense to biologists. Why would an animal cause itself harm? They whole point of living is to keep on living, and to make more of yourself, so why do we see so many different examples of altruism in nature? It turns out that altruistic behavior is often responsible for the continuation of a species. When an individual is willing to harm itself for the greater good, the species is more likely to become stronger and reproduce more. Think about families that pull together to raise a child, or worker bees that share the rearing of young. Without that support, the next generation would be very weak. The sacrifice of others, their altruistic behavior, ensures the success of the next generation.

Giving All For Family

So, when an individual is willing to give up his or her own well being for another, it's known as altruism. However, we've noticed that altruistic behavior isn't nearly as common among unrelated individuals as it is among family members. Maybe this action is so 'selfless' after all! This observation brought about the theory of kin selection.

While we thought the biological imperative acted on each and every individual organism, it apparently also works on genes. This is why you feel such a connection to your new baby niece, or want to protect your little sister, even if it means taking on the local bully. Your genes want you to protect your family. Think about this the next time you watch a honeybee give her life to protect the hive, or observe a kid defending his sister's honor. You're watching kin selection at work.

Summary

Kin selection is a type of altruistic behavior that helps ensure closely related family members will survive, even if it means the injury or death of an individual. Kin selection is a form of natural selection that is seen in nature, from humans to insects to everything in between.

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