You're stuck in the stone age.  

Sure, genetically you're 100 percent Homo sapiens, but some of your health habits are practically prehistoric. Everything evolves, including the research on what does and doesn't work to keep our species alive. That means you may be trying to fight death and disease with the equivalent of flint arrowheads.

So how do you know what's obsolete and what isn't?

After surveying nearly 500 guys, we came up with a carbon-dated list of fossilized strategies and the 2015 tips to replace them.

How many times a day do you brush your teeth?

Once a day: 28%
After each meal: 6%
Twice a day, morning and evening: 66%

You clean your teeth in the a.m. and p.m., so why not at noon too? Because those extra brush strokes can erode your enamel, especially if you just ate some acidic foods for lunch, says Jeffrey M. Cole, D.D.S., the 2013 president of the Academy of General Dentistry.

That means your best dental intentions may damage your choppers, leaving your mouth more prone to cavities, gum disease, and decay.

While three times is too many, once isn't enough.

Unless you have perfect brushing technique (few do), one pass is bound to miss spots, says MH dentistry advisor Mark S. Wolff, D.D.S., Ph.D. Use the rule of twos:

Brush twice a day for two minutes each time. At midday, use floss to make your mouth presentable after lunch.

(Brushing isn't the only way to protect your smile. Here's How Coffee Can Save Your Teeth.)

What do you do when you're running a fever?

Take an OTC fever reducer: 44%
Cool down with a cold compress: 6%
Just let it run its course: 50%

Running a fever isn't so much a sign that you're sick as it is a billboard that you're trying to heal.

How so? An increase of just 1 to 2 degrees in your body temperature boosts the productivity of your immune cells and helps them fight off infection, says Elizabeth Repasky, Ph.D., a researcher at Roswell Park Cancer Institute in Buffalo.

That means the 44 percent of guys who pop pills, and the 6 percent who try to cool down, may actually be taking the infection's side in the battle.

When you have a fever, your body shivers, signaling you to move to a warmer spot—such as under the covers.

"The general advice now is 'Don't fight that urge,'" Repasky says. The exception: Seek help if your fever hits 103°F or higher or is persistent— lasting longer than three days.

What do you do to clean and treat a wound or cut?

Rinse it with water; then bandage it: 29%
Let it breathe until it scabs over: 40%
Clean it with hydrogen peroxide: 31%

Congratulations: You're all doing it wrong.

For the 40 percent of tough guys who think bandages are for babies, that battle wound may turn into an ugly scar, say Harvard Medical School researchers.

They found that letting a wound scab over instead of keeping it moist is more likely to cause inflammation, which extends healing time and can result in unwanted scarring.

And while the sting of hydrogen peroxide makes you think it's working, the stuff is ineffective at stifling bacteria, a University of Miami study review found.

As for OTC antibiotic ointments, they're known to cause skin reactions, says Texas-based dermatologist Anna Drosou, M.D. So wash your hands, and then flush the cut with water. Next, add a dab of petroleum jelly to keep it moist. Apply a bandage.

How do you typically deal with back pain?

Pop a Tylenol and pray for relief: 12%
Ice, heat, and rest until the pain stops: 14%
Try to keep moving and stay mobile: 74%

We get the logic: When in pain, take a pain pill. But a back attack doesn't listen to logic.

Last year a Lancet study found that popping acetaminophen for lower-back pain was no better than swallowing a sugar pill. And an Australian study review concluded that heating your back may provide brief relief, but the evidence that icing works at all is lacking.

There's only one way to escape the stranglehold on your spine: Move.

"People are often scared of movement, but it's the best thing for healing a back," says Christopher Maher, Ph.D., lead author of the Lancet study.

Just avoid pushing too hard too soon, he advises. Begin by taking a simple walk around the block, and then gradually up the activity ante over the next couple of weeks.

(Put down those pills and check out these 6 Ways to Beat Back Pain.)

How do you stay hydrated throughout the day?

Drink eight glasses of water: 54%
Drink whenI’m thirsty: 20%
Drink whatever makes me pee: 26%

Water is good for you. And it's the world's most boring beverage. Hence the dilemma faced by anyone who's tried to drink eight glasses of H2O a day.

So stop trying.

The eight-glasses rule is arbitrary, says Stavros Kavouras, Ph.D., an associate professor at the University of Arkansas who studies hydration. Depending on your activity level, diet, age, and climate, you may need more or less than that exalted eight anyway.

Rather than tracking your fluid consumption, count how many times you unzip at the urinal.

When Kavouras and his team studied the number of daily bathroom visits that correlate with adequate hydration, they came up with... five. You can also judge the color of your stream. If it looks like lemonade or lighter, you're golden.