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The Age When Birds Ruled The Earth

SciBlogs editorial staff looks at the meaning of dominance. Did dinosaurs ever really rule the Earth? Did they ever stop? And what does it mean to be “dominant”?


Two Willet birds in silhouette (Tringa semipalmata; formerly Catoptrophorus semipalmatus) on Morro Strand State Beach. From Flickr, by mikebaird

Yesterday on Not Exactly Rocket Science Ed talked about a new paper in the journal Science that looks at the diversification of large vertebrates after the Triassic/Jurassic extinction event. In simple terms, how did dinosaurs take over the Earth? I think the article and Ed’s response begs an interesting question. Namely, what does domination mean? Ed says “Today, living dinosaurs – the birds – still rule our skies and back in their heyday, they were the dominant back-boned animals on land for millions of years.” Were the dominant back-boned animals? Today birds are without a doubt the most diverse terrestrial vertebrates and total bird biomass exceeds mammal biomass by a long shot. So who’s really dominating whom? For many birds, we clean their shit, help them breed and feed them. Sounds like they’re the ones in charge. The point isn’t that we need to free ourselves from our avian oppressors. Rather, the concept of dominance doesn’t seem to be very scientific. Biodiversity? Sure. Biomass? Why not. But dominance? Ruling the Earth? Those are terms that don’t really mean anything in a scientific sense because, in the end, as Stephen Gould put it, isn’t every age the Age of Bacteria anyway?