'The Dead are our nearest neighbour' -John O'Donohue
Our relationship with family/tribe members does not stop when they cease to live in this realm; they remain an integral part of our living community. Everything that we ARE we OWE to our Ancestors, this goes much further and much deeper than just our physical traits.
Our DNA is intelligent in its own right, carrying vast amounts of information that is far in excess of just regulating what colour hair/eyes we have, whether we are tall/short, skinny/podgy or destined to be a great athlete (insert any inherited gift/skill).
Science is just beginning to discover how this works (the field of study is called epigenetics), information from experiences is added as an extra layer of information on top of our DNA sequence, it doesn't change the DNA sequence itself but acts more like putting a layer of clothes on it, this information is passed on to future generations; it is believed that this is the mechanism by which instincts occur in animals (including humans).
In 2013 Scientists in the UK stored about a megabyte's worth of text, images and speech into a speck of DNA and then retrieved that data back almost faultlessly (http://physicsworld.com).
Our DNA is therefore capable of acting like a high-density hard drive of a computer and contains knowledge gained through experience by our Ancestors.
Our personal programming is just the tip of the iceberg, our consciousness and the physical world are intertwined; a scientific experiment called the 'Double Slit Experiment' produced some mind-boggling weird results - scientists knew that when you pass 'waves' through two narrow slits to a screen behind you get an 'interference' pattern on the screen because they bounce off each other (any waves do it; light, water or sound) but when you pass matter through you get a pattern of two lines on the screen as matter has to go through one slot or the other - Simples !
Now do the same at the quantum level with electrons (very tiny bits of matter) - you should get the same two line pattern but you don't, you get an interference pattern as if the matter was behaving like waves - WHAT!
THAT isn't the weird part, the scientists decided to set up detectors in front of each slit to determine what was really going on, as soon as the electrons were being observed by the detectors they didn't produce the interference pattern (and it didn't matter where the detectors were placed; in front or behind) - take the detectors away and they do it again. SO - don't observe them and they do it - do observe them and they don't, just by observing an electron you can change the way it behaves.
HUMAN CONSCIOUSNESS ALTERS THE WORLD IN WHICH WE LIVE.
Our Ancestors are not just those of our physical genetics (Ancestors of Time), they are also those who have lived within the same culture and held the same philosophies as us, venerating that which we venerate (Ancestors of Spirit) and those who have walked upon the actual geographical places that we walk (Ancestors of Place).
Communing with the ancestors is communing with life itself.