Can you help me understand this Biology question?

this the link for the article

1- why is the order Insectivore important to understanding the phylogenetic relationships with Placental mammals?

2- when do the authors feel that the “African Radiation” occured?

3- looking at the three phylogenies on Figure 1, briefly explain what is being represent here. what is the significance of the information being represented here?

4- Towards the end of the article, the authors discuss some aspects of reproductive isolation and Speciation they feel may be in play here, what are they? and What are they significant to their argument?