When scientists at Harvard University began tracking 268 Harvard sophomores in 1938, they thought the key to a long and happy life could be found in genetics and biology.

The researchers measured the participants' skulls and brow bridges, they took in-depth notes on the functioning of major organs, and they even analyzed the men's handwriting.

Original study subjects happened to include President John Kennedy and former Washington Post editor Ben Bradlee.

As technology advanced, researchers took blood and tested the subjects' DNA and cholesterol levels. They also expanded the study, first to 456 inner-city Boston residents who were not as wealthy or educated as the original Harvard sophomores and then to the children of the original subjects, who numbered 1,300 by the late 1960s.

Eighty years later, researchers have abandoned the idea that genetics, personality type, wealth, fame, or education are the keys to happiness. Turns out all you really need is love.

"The surprising finding is that our relationships and how happy we are in our relationships has a powerful influence on our health," study director Robert Waldinger told the Harvard Gazette. "Taking care of your body is important, but tending to your relationships is a form of self-care too."

Happy marriages, it turns out, are particularly important to happiness. Women who felt securely attached to their partners were less depressed and had better memory functions than those in unhappy marriages.

"Good relationships don't just protect our bodies; they protect our brains," Waldinger said in a separate TED Talk. "And those good relationships, they don't have to be smooth all the time. Some of our octogenarian couples could bicker with each other day in and day out, but as long as they felt that they could really count on the other when the going got tough, those arguments didn't take a toll on their memories."

So if you want to maximize your chances of a long and happy life, maybe spend less time at the office and more time loving the one you're with.