Kin Selection

“Helping a sister can alter the fate of shared variants, but it does not turn every family into harmony.”

01 / PLAINLY

What it means, plainly

Kin selection favors traits whose effects on relatives can outweigh their cost to the carrier.

02 / CONTEXT

A little more

Kin selection describes selection on traits that change genetic relatives' reproduction. Hamilton's rule compares benefit, relatedness, and cost; it is not a conscious calculator.

03 / WHY IT MATTERS

Why it matters

It helps explain cooperation, conflict, and care allocation among social insects, birds, mammals, and other organisms.

04 / EXAMPLE

A familiar example

A sterile worker may rear sisters; explaining the system also requires ecology, relatedness, and available alternatives.

05 / LIMIT

What it does not mean

It does not say all relatives cooperate: family members share genes but can also compete for food and care.

06 / NOTICE

Notice it in your day

Compare help given to a relative with help given to a stranger; add reciprocity and see whether the explanation changes.

FINAL NOTE

The idea worth keeping

Use relatedness as one weight in a balance, not as a complete explanation or a moral obligation.

QUESTIONS / 02

Questions people still have

Does kinship mean automatic cooperation?

No. It can favor help under particular cost-benefit relations, but conflict among relatives also occurs.

Is Hamilton's rule a mental decision rule?

No. It summarizes evolutionary conditions for a trait to change frequency; an organism need not calculate it.