Grandmother as primary care giver?

The clinical evidence also points to elderly's natural inclination towards a new body, it's basic natural instincts. Grandpas can also be found of their spreading bloodline.

There is hardly any merit going to grandfathers because even though many of them show fondness for grandchildren, the plain truth is that they are not as nurturing as grandmothers.

Most men are deadbeat Dads, meaning that they are good for nothing but performing sexual acts which result in progeny. That does not mean that it is their fault, because after all maybe they are not endowed with the required nurturing tendencies as women are.

But a man can think it out and induce himself to contribute. That is possible. There is enough evidence to support that idea in a handful of males.

It is also possible that men (generally and traditionally) are wired or brought up to consider progeny in terms of expansion of bloodline, as for instance conquering in order to acquire and dominate.

We can notice for instance that practically all societies use the father's name as last name for identification, that is what is important to men. An exception of to that, that I am aware of is the matriarchal society of the Ashanti in Ghana, where the mother plays that role. The father may not know all his children, but the mother does as well as their fathers.

Generally and traditionally the women's approach is different, it is as rightfully noted more nurturing. After all nature has endowed them biologically for that.

That said both feel the connection to progeny with the ulterior subtle motivation of a future body, that has to be baked in regardless of gender or species. And, being a disinterested (useless) father does not negate the need for the next body. Understandably nurturing and reproduction are two very distinct characteristics.

The colonial registration process which lists the father and made it acceptable to tag the child at birth to a male by a surname, is designed to identify the father as the person responsible for the bills of the mother and child.

In some cultures like in South Korea, the surname is the first name but even that has to do with identifying the man for liabilities of the mother and child, especially for paying money for expenses related.

In Europe (England included) there was bans-of-marriage, which were announcements in the town square. This was a declaration of the intent to marry. It was made to alert everyone that such and such lady was to be married shortly to such such man. But the idea here was to expose other marital or sexual liabilities that the man or woman may have at the time, especially the man, so that people knew that he would be in a position to legally generate children at an upcoming marriage, and they could object to the wedding by showing that he had children (reproductive expenses) elsewhere.

The aristocratic class (king/queen and relatives) wanted to have nothing to do with the expenses incurred by the serfs' sexual activity. Thus they tagged the father's name to the child to make it easy to identify him for liabilities.