“New England is the place where grandparents were invented. It was one of the first places on earth where people routinely lived old enough to have a full biblical three score and ten, and then some.”

So stated Jane Kamensky, a historian on the Brandeis faculty, in answer to a question posed by me. At a meeting of the writers’ group PEN New England, I had asked whether she and her fellow author, Jill Lepore, had included any old people like me in their 2008 novel Blindspot.

Kamensky went on to explain that even though the novel centers on young people, older characters have a meaningful role in the story. “During a dizzying political moment like the 1760s,” she said, “the accrued knowledge of people in their 60s and 70s is important in the novel.”

At first, crediting New England with the invention of grandparenthood made me smile with pleasure. To think of our region playing such a dramatic part in the evolution of family structure stirred my imagination and briefly enriched my fantasy life.

On more sober reflection, however, I realize that grandparents arose in human history a long time before the 18th century. In fact, some would trace this happening back to the earliest days of human development, perhaps a million years ago.

And they appeared in places far removed from New England. Wherever humans evolved from their animal origins, they would have begun to reach across generations.

That’s the evolutionary approach to grandparenthood taken by Bill Thomas, a physician from New York State, in his book “What Are Old People For?.” Thomas envisions the first grandmother helping her daughter who has just given birth.

For Thomas, this event is momentous: By assisting the new mother, the grandmother has enabled human beings to develop as they never could have otherwise.

The involvement of grandparents, especially grandmothers, gives humans advantages that go far beyond those of their cousins, the chimpanzees. They make it possible for the human brain to expand its power, much surpassing what the smartest animal could muster.

For Thomas, “the thing that may well have set the course for the evolution of the modern human, is the day when food was shared across three generations. This revolutionary act changed the course of life on Earth.”

This physician goes so far as to state: “We are what we are because of the changes that grandparenting made possible.”

I find this approach creative and marvelously stimulating. Reluctantly, however, I judge that the thesis claims too much. Was the grandmother’s primeval role really all that decisive in the development of the human race?

And what about grandfathers? Bill Thomas would seem not to have saved any role for them. For me, grandfathers continue to offer fascination.

Two cases in point are two fellows known to me for decades but who became grandparents only in the last few years.

The first, let’s call him David, demonstrates the power of grandfatherhood to change personality. Thanks to contact with his son’s two children, he has gone from being famously difficult in some of his relationships, to becoming downright sociable, at least with me.

At first, I attributed this change to the mellowing that the arrival of one’s 60’s, 70’s, and 80’s often brings. But, no, this fellow seems to be moved mostly by his grandpaternity.

When I spoke with him about a recent visit he had with the children, he lit up with enthusiasm about them. Nothing, it seems, now gives him more pleasure than seeing them. It has been enough to turn a problematic personality into one that values human contact

The other grandfather, Michael, finds being with his two young granddaughters stimulating, both physically and psychically.  He speaks of “a tremendous enthusiasm and infatuation that I would not have expected.” He also mentions the physical effort that their activities require.

More important, perhaps, he identifies “a pulling into the future – grandparenthood is anti death.”

The sociologist Theodore Rozak backs up this latter approach.  In “The Making of an Elder Culture,” he asks what grandparents see in their grandchildren.

His answer: “They see life renewing itself, a small antidote to mortality. All that we humans value most but see slipping away is reborn in the young–hope, vitality, wonder, innocence. Children are the delicate shields we raise against death. That is why we hold them dear.”

Does grandparenthood stave off fear of the end of life? Are children, in Rozak’s impelling phrase, “the delicate shields we raise against death?”

I don’t know much about that. More likely, it seems to me, is the power of grandparenthood to extend life. By putting us in touch with new life, life connected to us, it can make it value our own more.

That’s the way it was with my parents-in-law. Our daughter, their first local grandchild, was an accessible and constant delight to them in the last decade of their lives.