My assumption as someone not formally trained in advanced biology is that the phylogenetic tree has an implied arrow of time, and each node of the tree is a point where a mutation occurred that was sufficient to create a new and separate family/order/genus/etc afterwards, with leaf nodes representing species.
In this sense a cycle can’t occur because a branch would need to reach back in time and rejoin with an ancestral branch. It would be a different kind of grandfather paradox: who would be the ancestor and who the descendant in a cycle?
Maybe someone could help point out the flaws in this model.
Your assumption is true, but only for rooted phylogenetic trees. In unrooted trees the node representing the most ancestral state is absent and thus no directionality can be determined.
Comments
My assumption as someone not formally trained in advanced biology is that the phylogenetic tree has an implied arrow of time, and each node of the tree is a point where a mutation occurred that was sufficient to create a new and separate family/order/genus/etc afterwards, with leaf nodes representing species.
In this sense a cycle can’t occur because a branch would need to reach back in time and rejoin with an ancestral branch. It would be a different kind of grandfather paradox: who would be the ancestor and who the descendant in a cycle?
Maybe someone could help point out the flaws in this model.
Your assumption is true, but only for rooted phylogenetic trees. In unrooted trees the node representing the most ancestral state is absent and thus no directionality can be determined.