I don't think we can really contact the dead.
However, there is a sort of "genetic memory".
A great many of my own ancestors are buried in the same churchyard. And I have often sat amongst the graves, and "imagined" their lives.I know all their names, and much of how they lived. And when I sit there and meditate, I can almost "feel" their presence.
I have traced my family back a long way (to 1349), and it does give me a sense of calm sitting amongst them.
So, I don't really know if I make "actual" contact.
I certainly don't give much score to Spiritual Mediums! But, we don't really know, do we?
I would say that the more we learn about our ancestors, the more we feel that they are "still here" with us.