You weren’t looking for it. No, you were searching your calendar for something else but, as you flipped the pages, there it was: Christmas. It’s coming, and though the weather still says “summer,” you’ll have to start your dreaded gift list soon.

And that list keeps growing, much to your chagrin. So why do you do it? If you read “The Consuming Instinct” by Gad Saad, you’ll see that the right gift – and helping your customers find it – is really a matter of DNA.

Ugh, you just remembered: before Christmas you’ve got three birthdays, a wedding, and a baby shower to deal with. Gad Saad says that the decision to give gifts comes from evolution. We’re wired for it, in fact, with almost every decision we make winds back to consumerism.

There are, he says, four Darwinian reasons for consuming: survival, reproduction, kin selection (relationship management) and reciprocity. And no matter what, an “infinite advertising budget” won’t change what our biology says we have to have.

Evolution, for instance, makes us crave foods that are bad for us. We’re prone to what scientists call a “variety effect.” The bigger the food variety, the more we eat, and if it’s fatty, our brains think that’s even better. This, Saad says, explains why buffets are so popular and why there are literally hundreds of choices of breakfast cereals.

Because choosing a mate is “the ultimate consumption decision,” the things we do to attract that SigO are evolutionarily instilled by gender. Men, biologically-speaking, use flash to attract females (think peacocks). Women, on the other hand, shop for “good genes.” In both cases, Saad says, we are hierarchical and deferential to someone who has “kept up with the Joneses.”

And that gift-giving you struggle with? If it’s courtship-based, it’s loaded with more meaning than, say, the toy you’d buy for your nephew. But gift-giving, whether event-driven or as a you-scratch-my-back, I’ll-scratch-yours reciprocity is the glue that holds our Darwinian-influenced society together.

So is this a business book or not? The answer is yes – and no.

The copyright page says it’s about “economics.” Author Gad Saad is a professor of marketing at the John Molson School of Business at Concordia University. But “The Consuming Instinct” is too steeped in evolutionary science to be of much interest to a businessperson who needs information NOW.

That doesn’t mean you should pass it up, though.

Take the time to look between the lines of this book and you’ll be rewarded with delightfully droll nuggets of marketing information based in biology. Saad explains why we crave Ferraris when old beaters will get us to the same destinations. He describes the “Darwinian roots of advertising effectiveness.” And he reveals how color, frequency and voice-over can make or break your ads.

If you have time and want to add science to your business; if you need an excuse to go shopping; or if you wonder why you bother gifting the unappreciative, “The Consuming Instinct” is worth digging through. For you, it’ll be very ho-ho-helpful.

Terri Schlichenmeyer’s reviews of business books are read in more than 260 publications in the U.S. and Canada.