The spacecraft made a slow descent through the blue clouds above the Missouri River. A hairline trail of green exhaust streamed from its rear vents, as it started a slow curl above the carefully picked valley below. When it landed, out came two little baby alligators who, although tiny compared to Earth's crocodilians, made up for their size with intelligence, humor, and a rare sense of the apropos.

Harlan, the smaller of the two, was five inches long and three inches wide when his arms stretched flat along the ground. Sixsix, his older brother, was a full two inches longer but only a half-inch wider owing to the fact that his belly was too stuck out to permit much stretching on the ground. Being amateur linguists, they had chosen before their voyage to communicate for however long the trip would last in a defunct language called English, in particular that dialect which flourished on this same continent four thousand years prior, during what used to be called the Twentieth Century.

"Animals on this planet," Sixsix explained, "have grown much larger than on our own due to the difference in specific gravity. The ratio is roughly a baker's dozen to one."

Harlan nodded sagely and, while his brother was scanning the horizon, stole a peek at his lexicon to determine the contemporary meaning of the qualifier "baker's".

"Any gravitational ratio in excess of ten to one, you will remember," Sixsix went on, "will in addition imply significant metabolic discrepancies as well. For instance, the limiting speed of neural signals being one of the few biological constants in the universe, organisms of differing sizes must compensate in other ways for the relative speed or slowness of their muscular and sensory networks."

Harlan burped.

"I'm hungry," he said, adding a slightly plaintive whine to his voice.

"Well, we don't have any food on board," said Sixsix.

"Let's go home, then," said his brother.

"Okay " Sixsix tried to hide his disappointment in his brother for not showing more interest in interplanetary biology. The two little beasts waddled back to the ladder handing from their cigar-shaped saucer, wandered up into the craft, and whirred back to their home in Alpha Centauri where their mother was at that very moment preparing a nice spaghetti dinner.