By squeezing the food and pushing it towards the digestive juices in your stomach
Speciation is not a mechanism of microevolution.
Since it is the hearts job to pump blood throughout the body of the organism, the circulatory system would fail and the entire organism would suffer if the heart cells stopped working properly.
No. Medical progress is allowing us to progress and evolve in different ways. That is the only difference. Having medical progress and good medical care allows us to pursue different types of activites we wouldn't be able to pursue otherwise. This at the same time brings a different type of evolution.
