[揽瓜阁精读] 228.鸟的羽毛

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228 鸟的羽毛
P1: two hypotheses 1. metabolism is needed for a highly active small predators like Dave, and its rate is regulated internally not outside environment. Dave’s body feathers allow him to retain heat and energy.
P2: 2. hypothesis: feathers were useful for courtship and other social interactions. Like reproduction
P3:though explain why, but not focus on one more likely. Filling gaps