Proposed number of Hox genes in some extant and extinct animal groups $\begin{array} { | c | c | c | c | } \hline \begin{array} { c } \text { Last Common } \\\text { Ancestor of Bilateria }\end{array} & \begin{array} { c } \text { Last Common Ancesto } \\\text { of Insects and } \\\text { Vertebrates }\end{array} & \text { Ancestral Verte brates } & \text { Mammals } \\\hline 4 & 7 & 14 & 38 \\\hline\end{array}$ Which of the following is the most parsimonious explanation for the change in the number of Hox genes from the last common ancestor of insects and vertebrates to ancestral vertebrates, as shown in the table provided?

Question

Proposed number of Hox genes in some extant and extinct animal groups

\begin{array} { | c | c | c | c | } \hline \begin{array} { c } \text { Last Common } \\\text { Ancestor of Bilateria }\end{array} & \begin{array} { c } \text { Last Common Ancesto } \\\text { of Insects and } \\\text { Vertebrates }\end{array} & \text { Ancestral Verte brates } & \text { Mammals } \\\hline 4 & 7 & 14 & 38 \\\hline\end{array}

Which of the following is the most parsimonious explanation for the change in the number of Hox genes from the last common ancestor of insects and vertebrates to ancestral vertebrates, as shown in the table provided?