The Hitchhiker's Guide To Altruism -- Study Explains How Costly Traits Evolve

... Darwin explained how beneficial traits accumulate in natural populations, but how do costly traits evolve? In the past, two theories have addressed this problem. The theory of hitchhiking suggests that genes that confer a cost to their bearer can become common in natural populations when they "hitch a ride" with fitter genes that are being favored by natural selection. [click link for full article] ...