Mammal domination

[Halichoeres]

@BlueKrono: Yeah, I think Diamond's book is a good analogy. Success is always contingent, things aren't better or worse at life, just better or worse at it in the particular context they find themselves in.

@stargatedalek: It's true that larger animals require more energy for basic maintenance, and that's great as long as resources are abundant, but we can see from the fossil record that they're much more prone to extinction. If you use venom to subdue prey, you 1) spend some energy making venom proteins, which can be more or less expensive depending on the constituents, but maybe less than if you had to chase and grapple with it, and 2) have more energy to devote to reproduction, which is the canonical definition of fitness. There is a trade off between rate of reproduction and likelihood of survival to adulthood (r versus K in population biology), and there is a trade off between individual growth and reproductive effort. But they're all allocating the same resource, namely, energy.

As an example, Hymenopteran insects are obviously extremely successful at small individual body sizes, but they have enormous population sizes, which are equivalent from an energy flow standpoint. Eusocial insects in particular are sort of the best of both worlds--large colonies produce phenomenal energy flux, but they are probably less vulnerable to extinction than a single organism of similar mass because in at least some species, they can get by with just having smaller colonies for a while.

[Papi-Anon]

Interesting stuff, Halichoeres!

I've often thought that there was no real universal 'fitness' and that it was more based on conditions being favorable to certain organisms to live longer, grow larger, and have more success generating offspring that make it to reproductive capability. Most of what you said was indeed material I'd thought about and postulated. Great to know I wasn't too far off!