How Mr. Spock taught the kids about evolution (with lesson plan)

"It has to do with ... biology." - Spock

Love is rough on a Vulcan man. Every few years he goes into heat and feverishly races back to the planet Vulcan to mate with the wife. Trouble is, the wife might decide she'd rather have him fight some other Vulcan guy to the death. Winner gets the girl. The whole unpleasant arrangement seems to be enforced by one old lady and a bunch of dudes jangling racks of sleigh bells. Whatever.

"Wait," says Izzy (12) as we discuss these finer points over dinner, "wouldn't that affect Vulcan evolution?"

Ta-daa! Why yes, honey, I believe it would!

Cue the all-family viewing of "Amok Time," the classic episode in which Spock loses the rationality, hurls a bowl of hot soup at Nurse Chapel, and commandeers the Enterprise back to Vulcan. "It has to do with ... biology, Captain" he spits out. I could write a book on the weird gender politics of what goes down with Spock and his capricious-yet-logical wife, T-Pring, back on Vulcan, but that's not what you're here for.

Caleb (9) was interested in how the women choose which guys to mate with and which have to fight it out. "Maybe they mate with the handsome ones and send the ugly ones to fight," I suggest. Here's how we worked out the evolutionary situation:

In about six generations, there are no ugly Vulcan men left at all. In fact they have evolved to be 100% Jon-Hamm-quality handsome! And all due to the whims of the ladies and their taste in looks.

Welcome to the weird world of sexual selection, where the female gets it into her head to select a mate based on some ornamental characteristic that may or may not be favorable to the animal. It can lead to spectacular biological sideshows, like the tail of the peacock or the elaborate dances performed by birds of paradise. Ever wonder how Vulcans got those pointy ears?

Caleb, world-renowned Vulcan evolutionary biologist,
shown with calculations. 

The kids pile on from all sides with objections. What if some women find the ugly ones handsome? Some of the babies have to be girls or Vulcans would go extinct! Handsome dads don't always have handsome kids! Vulcans have a mating season every seven years, so what about families with more than one kid? What about the women, aren't they evolving too? The stronger men win the fights, so would the ugly men evolve super-strength?

And my favorite objection, from Caleb: "But Mom, handsome men don't necessarily make good mates. What if they're handsome and mean?"

So here's the lesson plan.

Step 1: Watch "Amok Time" with the kids. (Explain that in the future, all women will be forced to wear miniskirts and sport wildly complex hairdos.) 

Step 2: Print out the image above and work it through a few times with the kids. Watch the kids' faces light up with understanding until...

Step 3: Field the inevitable objections. Many can be worked into the model. One time through, for example, we gave the handsome men a 20% chance of having an ugly baby. This slowed the evolution toward handsomeness but didn't change the outcome. Same result with making half the babies girls. And so on.

Dang, it was fun.