[jeddavis]

The real question: If those kinds of sizes were such a winning ticket for creatures which supposedly dominated the planet for tens of millions of years.... then why in the 70,000,000 years which supposedly has passed since they went away, has nothing else ever re-evolved to such sizes? Evolving to different sizes should be fairly easy.

[AFreeBird]

The real question: If those kinds of sizes were such a winning ticket for creatures which supposedly dominated the planet for tens of millions of years.... then why in the 70,000,000 years which supposedly has passed since they went away, has nothing else ever re-evolved to such sizes? Evolving to different sizes should be fairly easy.

Competition for resources. Scarce resources means you adapt to the supply by being smaller and consuming less, or you die.

[Fred Nerks]

Evolving to different sizes should be fairly easy.

Adaptation - limited only by existing conditions?