Humans as an Evolutionary Force
The multitude of changes we have made to the biological world means that human actions probably now constitute Earth's most important evolutionary pressure. Let me repeat that. We are shaping the evolution of other species.
Charles Darwin, like many of us, believed that evolution was a slow process, occurring over millions of years. Another scientist, George Gaylord Simpson, disagreed. Although that is sometimes the case, it is not always. He believed that there were three paces of evolution, slow, medium and rapid.
Recently, increasing amounts of evidence is showing that rapid evolution does happen. And we are often the cause. We started changing the bodies and behaviours of animals when our ancestors first domesticated animals and plants - we directly manipulated evolution. Now, unintentionally and going largely unnoticed, we are doing the same thing to wild animals everywhere. Because today's rate of environmental change is so fast, evolution is occurring quickly.