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In uranium-lead dating, for instance, the radioactive decay of uranium into lead proceeds at a reliable rate. Based on the very old zircon rock from Australia we know that the Earth is at least 4.374 billion years old.
And that's how after rounding we know that earth is 4.5 years old.
I would say the environment. Animals have certain adaptations to certain environments to ensure they thrive in such conditions. Some animals do not have such adaptations at first but simply grow it over time as the environment changes. Therefore, I would say environment is expediting the rate of evolution.
Answer:
Spanish: La evolución es el proceso por el cual los organismos actuales se han descendido a partir de antepasados antiguos. ... La variabilidad genética es una parte fundamental del proceso, ya que la evolución se produce cuando fuerzas selectivas actúan sobre esa variabilidad.
English: Evolution is the process by which current organisms have been descended from ancient ancestors. ... Genetic variability is a fundamental part of the process, since evolution occurs when selective forces act on that variability.
Explanation: