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The theory of evolution by natural selection explains how species change over time. The core mechanism: within any population, individuals vary in traits. Some traits improve survival and reproduction in the current environment. Those individuals pass more genes to the next generation. Over many generations, the population shifts.
This isn't random chance. Natural selection is a sorting mechanism — it consistently favours traits that improve fitness in a given environment. But which traits help depends entirely on the environment. In a changing environment, evolution can happen surprisingly fast.
Evolution is supported by multiple independent lines of evidence: the fossil record showing gradual changes over time, genetic analysis showing shared ancestry, direct observation of evolution happening (bacteria developing antibiotic resistance, for example), and comparative anatomy showing homologous structures across species.
Humans share about 99% of our DNA with chimpanzees, about 85% with mice, and even about 60% with banana plants — we're not descended from chimps but share a common ancestor from about 6-7 million years ago.
by amirhassan13151
To understand "What is herd immunity 755", it helps to start from the underlying mechanism rather than the surface-level phenomenon. Scientists explain this through a combination of established theory and repeated experimental observation, which is what separates it from speculation. The core process involves a chain of cause and effect that can usually be demonstrated at a smaller, controlled scale. A frequent misconception is treating a simplified analogy as the literal mechanism, which can lead to incorrect conclusions. If you want to go deeper, looking at peer-reviewed sources or a textbook chapter on the topic will give a much more rigorous explanation than a summary can.
by whitneywalker23997