The frills were the central kinesic display. The reptilian Investors had long ribbed frills behind their heads, rainbow-tinted translucent skin netted with blood vessels. Frills had evolved for temperature control; they could be spread to absorb sunlight or opened in shade to dispel heat. In civilized Investor life they were a relic, like the human eyebrow, which had evolved to deflect sweat. Like the eyebrow, their social use was now paramount.