There are a lot of mysteries of the human body. But on Medical Monday we found 4 weird but true scientific facts about the body from Yahoo! Health.

1. Your heart health is predicted by your earlobes. Oddly enough, a diagonal crease - or lack of -- in your earlobe may determine the health of your heart. Although scientists are exploring the reason behind the link a 1992 study found those with an earlobe crease were far more likely to have coronary artery disease. In fact, this indicator was 94 percent accurate at predicting which patients had C-A-D, prompting the researchers to suggest that this weird clue be used to help identify at- risk patients.

2. Yawning is contagious, but less so in the summer. Seeing other people yawning-even in photos-can make you yawn in response.  However, a 2011 study showed that yawning in response to photos only happened 24 percent of the time in the summer, versus 45 percent of the time in the winter. Apparently, yawning cools down your brain a bit, so outside temperature makes a big difference in how likely you are to catch the urge. Scientists also found yawning also helps keep us alert, because -- It turns out that difficult mental tasks literally heat up the brain, while a yawn lowers the temperature. Another surprising finding: You can't complete a yawn with your eyes open.

3. You can literally smell fear. People can actually detect and respond to fear by smelling people's sweat. Research found there are different pheromones -- detectable chemical substances -- from armpit odor when people are afraid than when they aren't. Their fear can literally be picked up from their body odor.

 4. It's practically impossible to keep your eyes open when you sneeze. It's a simple reflex that prompts our peepers to blink shut during a sneeze, similar to the reflex that occurs when the doctor taps your knee with a medical mallet. While you can try to keep your eyes open when you sneeze, it's extremely difficult to do.

Be sure to check out this Yahoo! Health article for more weird facts about the body.