Human Beings Are Evolving in Real-Time
Do you live your daily life with the awareness that humans are still evolving? Yes, your species hasn't stopped it's evolution.
We always think of evolution as some distant thing, part of our history and an event our ancestors experienced, but centuries to come we'll be the ancestors of future generations.
Right now, on the Tibetan Plateau, the people there live in conditions most of us can't handle. They’ve been living there for over 10,000 years and now their bodies have somehow figured out a way to endure something the rest of us can't endure even for a few hours.
Living up that high is basically like living at the top of Mount Everest, the oxygen there is so little. I might get altitude sickness just thinking about it trying to live there, but these people have evolved traits making hypoxia almost no big deal for them.
It's not as if they have super high hemoglobin like you'd expect. In fact, the women with most kids, the ones passing on more of their genes actually have hemoglobin levels most similar to typical sea-level dwellers so it's got nothing to do with hemoglobin levels.
What differentiates them for the average person is how great a job their bodies do with saturating an average amount of blood with oxygen. They've been able to achieve this sweet spot where their hearts are no longer pumping too hard but they're getting enough oxygen at the same time.