Scott Sampson talks about dinasour evolution and notes that:
Ecologically speaking, once two closely related species differing only in reproductive structures (e.g., horns, frills, crests, etc.) come back into contact, it’s unlikely that both will persist for very long, since they will be doing the same thing to make a living.
As humans spread accross the planet, they developed various local cultures to support mate selection and reproduction. Does increased inter-cultural intercourse mean that we should expect to see the extinctions of peoples or cultures? Can a local agrarian culture compete against low cost food produced by agri-business? Can boring European music compete with the mutation of African drumming culture into rock-n-roll? If farming roles or music tastes are part of a mating dance, how does globalization affect mating prospects?
He also makes an argument for protectionist industrial policy:
When all of the continents were united as Pangaea, and even during the initial phases of fragmentation, virtually every terrestrial ecosystem for which we have good data indicates the presence of multiple, perhaps two to four, kinds of large carnivorous dinosaurs, in the range of 750-2000 kg. Given the extensive continental connections, this was a time when terrestrial animals were able to move around much of the planet. It is also why we find remains of dinosaurs on every continent. They didn’t need to fly or swim across major marine barriers—they simply walked from landmass to landmass. With all of this faunal mixing, it is not surprising that we find multiple species of large carnivores in most ecosystems.
Unlike living carnivorous mammals, which often have highly specialized teeth and jaws for particular diets (meat, bone marrow, etc.), large carnivorous dinosaurs apparently lacked such ecological diversity. So, given that they were all doing pretty much the same thing to make a living, it seems reasonable to postulate that inter-species competition would have limited the maximal body size for any one species. It’s highly unlikely that a given lineage could have evolved to be a giant of five or six tonnes when several other species were in direct competition in the same ecosystem. As the continents split apart, dinosaurs and all other parts of the terrestrial biota went along for the ride on these giant rafts of continental crust, setting sail on independent different evolutionary courses. We postulate that it was only after all the continents broke apart that opportunities arose for a single species to dominate an ecosystem and grow to T. rex proportions.
About 75 million years ago, when North America was divided into two landmasses by a seaway, several smaller-bodied tyrannosaurs such as Daspletosaurus and Gorgosaurus lived alongside one another. These animals were large, about 1,000 to 2,000 kg, and no doubt menacing, yet a fraction the size of their subsequent relative, Tyrannosaurus rex, which lived about 67-65 million years ago. In contrast to its predecessors, T. rex lacked the direct competition with other large carnivores. For whatever reason, all other tyrannosaur lineages died out. Almost simultaneously, the seaway receded for good, reconnecting east and west America for the first time in 25 million years and effectively doubling the geographic area for North American dinosaurs. The additional area allowed Tyrannosaurus to increase in body size while maintaining population densities high enough to avoid extinction, at least for awhile.
I don’t buy it. Why wouldn’t the same be true of members of a single species in the same business?