As you climb higher up the mountain it gets harder and harder to breathe. Sometimes you feel sick and dizzy. Why is that? Because you don’t have physiological mechanisms for dealing with low oxygen levels. In simpler terms, your body can not work well when you don't have the normal amount of oxygen. Although you can’t live at high heights, some people can. People like the Tibetan Sherpas have a gene (a stretched EPAS1 gene) that helps them live at high heights. Genes are things that tell what the cell is. It gives the information of if the thing is a plant or animal. In this case, the gene that the Sherpas have makes them produce less red blood cells.

A theory called natural selection chose this particular gene to survive in the Sherpa genes. Natural selection ensures that only the organism that has the characteristics that will be very helpful in the environment will continue to show in the organisms. The stretched EPAS1 gene that makes the body naturally make less red blood cells is helpful because if your body makes too many red blood cells your veins could clog and form a thing called clots. If the blood clots, it can lead to a heart attack and even death!

Not everyone has this helpful gene because it must be passed down by the parents that have the gene. The offspring, or kid, has the gene, it means at least one of the parents had the gene and this child can then pass the trait down. The people that have this gene are special because almost nobody else in the world has the gene besides them! These people have not spread the gene, because none of them have made babies with people out of their exclusive gene pool. If the people with the gene mated with other people then eventually over lots and lots of generations, the gene could be spread to more of the human population. If there was change soon then the results still wouldn’t show until thousands of years. Maybe someday everyone will have this fascinating gene and our future generations can all climb Mount Everest without oxygen aids to climb. Only time will tell.