The issue focused on knowing how long all genetic variations might take to evolve and why scientists believe genetic variants change only after genetic mutations occur. Scientists cannot determine whether genetic variants cause diseases like ALS or Parkinson's because genetic modifications happen during childhood and genetic mutations occur later in life. Scientists must therefore estimate how long genetic variants might take to evolve and predict how disease progresses in humans. Scientists must then compare genetic variants between genetic variants from genetic variants from biological samples that didn't carry genetic mutations with genetic variants from biological samples that didn