Genetic Drift on the Colorado River

Genetic drift is a change in population due to random, chance events, such as a flash flood. When Dr. B was discussing this topic in class last week, she brought up a story from her friend. She said her friend had spent time river rafting and camping on a river when he nearly got swept away by a flash flood in the middle of the night. Her friend was the only one who camped low enough on the shore to feel the effects of the flood, as everyone else in his party was camping further up. 

This story reminded me of a recent river rafting trip I took on the Colorado River. We covered roughly one hundred miles and spent five nights camping along the shore. It was a rainy week, so we were constantly bundled up in rain gear and covered in mud. One day, about half way through our trip, we covered less mileage than expected and had to camp at the nearest sand bank. This sand bank was a few inches above the river and not an ideal place to stop, but it was the best option for the night. The worst thunderstorm I've ever witnessed took place that night. We now refer to it as the night of "The Incident". The wind was so strong that the poles of my twin and her girlfriend's backpacking tent SNAPPED. It rained so hard that the water levels started to rise and our camp suddenly became much smaller. The anchors holding the rafts to shore had to quickly be re-anchored. Another friend was camping with a tarp and it completely blew away. Loose items on the shore started blowing into the river. It was quite the night. If genetic drift had its way, our whole crew could have been lost in the river due to this random, chance event. Although slightly traumatic for some crew members, the night of "The Incident" ultimately brought us all together and we still shudder at the memory of it. Luckily, I've spent more nights on the Colorado River since then and have had perfectly clear weather. Phew!