When the rusty grey Jeep shuddered to a stop, we were straddling the top of deeply rutted dirt path. At last at the top of the incline, hours after we’d started our drive, my two friends and I stood awestruck overlooking Turrialba in Costa Rica. The house where we would stay was isolated on the top of a hill, presiding over coffee farms and swathes of high grass. The first taste of the terrain was fresh sugarcane. Our night guard, an old man with an even older dog and a machete, cut a short stalk for each of us to gnaw on.

Unpacking my suitcase into our two-room cabin, I scanned the landscape—lush, verdant hills and sweeping valleys in every direction. No store, restaurant, or room service for miles. This was more remote than many getaways tend to be. We had come prepared. We stocked up on provisions before making the hours-long trek, not knowing when we’d return, hoping we’d packed enough to eat.

When you’re in a new environment, you lose the food security of your own pantry, grocery store, or late-night delivery. You seek out solutions to the food question, which sometimes becomes vacationers’ most pleasant memories—a new restaurant, local fare, a culinary adventure. But in the distant past (and even for many people now), predicting the next meal was near impossible. It took work: scavenging, gathering, hunting, and the effort was shared by a group for efficiency’s sake. Returning to half a million years ago, we can see how humans’ eating habits began to shift away from their neighboring primates’.

Early hominids shared the African landscape with chimpanzees, and both species would have shared a diet comprised mostly of plants and periodically speckled with the meat of smaller mammals like the colobus monkey. The great peculiarity of early humans and perhaps their greatest evolutionary advantage was what they did with their meat after the hunt: they roasted it.

The firing of root vegetables or even a gazelle may very well have been accidental. Perhaps a Homo erectus bit into a sun-roasted root and liked it. If so, this early ancestor would have needed the curiosity and resourcefulness to experiment. By combining the power of fire with the food they consumed, early humans changed the trajectory of future generations.

There is evidence to suggest that cooking, more than the consumption of meat, encouraged our brains to grow and evolve into cleverer, more comprehensive minds. Cooking is a way of predigesting food, which allows some of the energy originally necessary for digestion to be reallocated. Some scientists believe a portion of that energy went to supporting the development of bigger brains.

The question that emerges is what brought on the enlargement of the neocortex? How did cleverness and politics fit into these early meals?

When I was thirteen, I went away to southern Illinois for my last week of summer camp before starting high school. I was one of the oldest girls there and spent the week hiking, canoeing, and rescuing a fifth grader from a patch of poison ivy in the middle of the night after she got lost trying to find the toilet. (Little did I know she was sleepwalking at the time, but that’s another story.) By the end of the week, I felt both energized and exhausted. I had spent nights out under the stars with friends surrounding me; I had capsized in the lake and swum to shore; I had gotten muddier and sweatier than I ever did playing junior high soccer. And when I finally came home, I was voracious. One of the clearest memories of that week is returning home after the hours-long drive and almost running up the stairs to our kitchen. I yanked open the door to our faded-lemon fridge and shoved into my mouth the first thing that appealed to me, which happened to be a rosy chunk of perfectly stewed meat.

Ah, to be thirteen and hungry.

I do think that as we expend energy, our bodies know what we need. It isn’t surprising now that what I needed then was protein. At the time, I felt shocked by the almost primal urgency that pushed me to eat a hunk of meat . . . cold, with my hands, dirt still under my fingernails.

But this isn’t far from where we started as a species. Meat was prized among primates for its energy-dense calories. Primates could satisfy their nutrient needs on vegetation alone, but meat was special—coveted, difficult to acquire, and even harder to secure a portion given the hierarchical and personally motivated distribution of portions by the community of chimpanzees’ alpha.

It takes a cunning alpha to process the politics of meat distribution: he uses it to humiliate lower-ranking males, secure alliances, and attract fertile females.

The dynamics are often dictatorial, but humans diverged from this system.

When Paleolithic humans began cooking, males tended to have a fifty percent larger body mass than females. Today’s men usually weigh in at only around fifteen percent larger. Why the shift from larger frames to smaller?

With primates, the ongoing competition between males for both food and a mate encouraged displays of aggression and dominance. But cooking introduced a dramatic shift in this dynamic. Men no longer needed to be the biggest or most powerful beings to ensure their survival and that of their offspring. They could rely on others. Instead of an instantaneous battle over the spoils from a hunt or waiting for an alpha male to disseminate the rations, there was a delay in consumption.

Cooking takes time. The meat and vegetables had to be assembled in a common area. A fire needed either to be built or maintained in the absence of the hunting party. Then an individual, perhaps one or more of the females, tended the food as it roasted in the fire. Any male could simply wait or even sneak some from the pile as it waited to be tossed in. There was no alpha in human tribes to control this through force.

If men could take food from the pile, so could females. For women, the motivation was often that of protecting their own offspring. Professor Craig Stanford, author of The Ape’s Gift: Meat-eating, Meat-sharing, and Human Evolution observes: “The common behavioral denominator even for social animals is individual nutrition, survival, and reproduction.”

Females needed to secure a sufficient ration of food to sustain themselves and any babies around at the time. But for a woman to compete with a man one-and-a-half times her size, she’d need cunning. She’d need help. She’d need another male.

Primate females are fertile for a short time in their cycle, and in most species, the signs of their fertility are obvious: swollen glands, an alluring aroma that signals to the male her reproductive readiness. But in modern human women, these signs are hidden. The probability of conception is mysterious and shrouded, and this is an effect of how our earliest female ancestors established food security. Women evolved physically to be perceived as “ready” in the reproductive sense throughout their cycle instead of only at the critical time. Their perpetual attractiveness developed to enable females to compete for a champion male, a “food guardian,” to help the women in securing enough food for themselves and their children. In a way, the more attractive the female, the more formidable a food guardian she could hope to secure. In the eyes of the male, the greater the female’s attractiveness (and the longer she exhibited such desirability), the greater were the male’s chances of ensuring his reproductive success.

These dynamics evolved slowly, becoming increasingly embedded in human culture as it became more hearth centric. The onset of cooking spawned a rough family dynamic within communities as these relationships formed. Because of the communal nature of roasting food, both men and women changed more than their neural capacity; they changed their physiology.