Hope springs eternal.

“Hope springs internal is more like it,” Lionel Tiger says coyly. Tiger is an evolutionary anthropologist at Rutgers University and the author of “Optimism: The Biology of Hope.”

Tiger’s research explores why people continue to make resolutions they won’t keep, and think positively despite massively bumming contrary evidence. “As hunter-gatherers we had no choice but to be optimistic,” he says. “We had to wake up each day and say, ‘Boy, it’s a better day than usual to catch an antelope.’” We had to say that every day, even when we’d eaten nothing but grass for three weeks. Optimism was around to counteract our own intelligence. If we didn’t overestimate our chances, we wouldn’t have even bothered to get out of the cave in the morning.

We make resolutions because they keep us alive.

“Human beings,” says Tiger, “can’t afford to be too cynical about their own behavior.”

And New Year’s Day is the opposite of cynicism. Always has been, way back to the beginning of resolutions in ancient Babylon. On the Babylonian calendar, the new year coincided with planting season; farmers resolved to return all borrowed plows and such. Later, Romans embodied the fresh-start concept of the day with Janus (from which we get January), the two-faced God who simultaneously looked forward and backward.

We innately seek opportunities for fresh starts that are tied not to our own resolve but to the sun, the seasons, the calendar. New Year, New You and all that jazz. But here’s the thing about when we were making those Roman resolutions: We were drunk. We were all still a-stupor from our New Year’s Eve celebrations, jacked up on the Roman equivalent of tequila shots.

It’s very similar to the Advil that marks New Year’s Day today.

“People tend to make resolutions after periods of debauchery,” says George Loewenstein, a researcher at Carnegie Mellon University.

Again with the cortices: “The part of our brains that is uniquely human can recall past behavior,” says Loewenstein. “But it’s very cognitive. ... What it can’t do is remember what you felt like” the last time you broke your resolution. The desperation. The lack of dignity. The digging in the garbage for the used coffee filter.

We make these New Year’s pledges not because we forget that we’ve failed, but because we think we have outsmarted the failure _ that this time, we can do better. Tomorrow is another day.

And so, resolutely, we resolve.