Hunger Is Our Secret Weapon

Nosy and hungry, she's the mother of us all

As mammals, we have big appetites. Cold-blooded bugs, fish, and lizards can get by on less food. A constrictor snake can go months without eating. We hot-blooded critters don’t have it that easy. Without food, a shrew dies in 5 hours. Keeping your body hot costs energy, even with fur. A mother secreting milk for her young uses up even more energy. It’s physiologically expensive to be a mammal, so mammals have no choice but to eat a lot more than reptiles. The need to keep eating or die seems like a hefty drawback, but we turned it into our special power. Hunger drove us mammals into evolutionary high gear.

Reptiles lead a slow motion life and spend a lot of time just hanging out, conserving their energy until it’s needed. The first shrews, on the other hand, learned to hunt quickly, racing through the night stuffing their toothy snouts with bugs. In the great Darwinian contest of life, reptiles competed against each other on a weekly schedule, but we mammals lived and died by the day. Natural selection worked faster with us, clearing out the less fit and rewarding the winners with multiple litters. And now we mammals dominate every environmental niche worth dominating.

What’s more, we humans have big, hungry brains. Our brains use up a fourth to a fifth of the body’s metabolic energy. Pressed to feed these hungry brains, our hominid forefathers ventured out onto the African savanna and began scavenging meat. In terms of sheer nutritional density, meat beats plants hands down, and hunger made meat eaters out of us. Returning to the tribe with meat, males finally had something special to offer their mates and children. With their new role to play as meat providers, males stopped being mere rabble rousers and became fathers. It’s incessant mammalian hunger that got us where we are today.


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