There are many different kinds of radiometric dating that are used to date things that are non-organic (which is part of how we determine the age of the Earth).
The reason carbon dating works is that the fresh carbon-14 gets mixed in with the rest of the carbon in the atmosphere and, since it’s chemically identical to regular carbon, gets worked into whatever is presently absorbing atmospheric carbon.
Biologists included principles from genetics in evolutionary theory during the 1920s and 1930s.
Between the mid-1930s and mid 1940s geneticists, systematists and palaeontologists collaborated to create a united approach to evolution, the "Modern Synthesis".
This is the beauty of fundamental research: you never know what you’ll find when you start poking around.
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