Discussion
With passage of time, the molecular distance between organisms increases during evolution due to :
Answer: C
The molecular distance grows because of Neutral mutations.
Kimura's neutral theory holds that most changes in DNA and protein sequences have no effect on fitness. Such neutral mutations are neither removed nor favoured by selection, so they accumulate at a roughly steady rate in separated lineages. The number of sequence differences therefore increases with time since divergence, which is the basis of the molecular clock.
Drift is the process that fixes neutral mutations, but drift alone, without new mutations, cannot add differences. Point mutations include harmful ones that selection removes, so they do not accumulate in proportion to time.
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