How do you account for the formation of ethane during the chlorination of methane?

(N/A) The chlorination of methane proceeds via a free radical chain mechanism,which involves three steps:
Step $1$: Initiation: The reaction begins with the homolytic cleavage of the $Cl-Cl$ bond: $Cl-Cl \xrightarrow{hv} 2\overset{\centerdot }{Cl}$.
Step $2$: Propagation: Chlorine free radicals attack methane molecules to generate methyl radicals: $CH_{4} + \overset{\centerdot }{Cl} \to \overset{\centerdot }{CH_{3}} + HCl$. These methyl radicals then react with $Cl_{2}$ to form methyl chloride: $\overset{\centerdot }{CH_{3}} + Cl-Cl \to CH_{3}Cl + \overset{\centerdot }{Cl}$.
Step $3$: Termination: The chain reaction terminates when free radicals combine. Ethane is formed by the combination of two methyl radicals: $\overset{\centerdot }{CH_{3}} + \overset{\centerdot }{CH_{3}} \to CH_{3}-CH_{3}$ (Ethane). Thus,ethane is obtained as a minor by-product during the termination step.