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"If an animal has a one- or two-year period in which to grow to maturity and reproduce, and it's trying to do that on a diet that's difficult to digest and not very nutritious, it's not surprising that it would evolve to be smaller. And it's also not surprising that when times are good again and carbon dioxide levels are lower and plants grow like they normally should, that the animals would go back to what we think of as their normal size."

He didn't mention that a siamese-cat-sized horse dissipates heat from its surface area more easily than a collie-sized horse. Internal volume is a cubic function. Surface area is a square function. Changes in size scale change the ratio of the volume to be cooled and the surface area available to cool it. Resistance to heat stress could be a selection factor in a world that is heating up.

My Uncle's pigs don't grow as big in the summer as they do in the winter...they don't eat as much when it's hot. Been observing that without any federal grants or special edumacatin'.