Exhibit A: an Olduvai chopping tool.
The journey starts, as you would expect, with something useful: a "stone chopping tool," believed to be about 1.8 million years old, suggests the dawning of a "relationship between humans and the things they create, which is both a love affair and a dependency," MacGregor says.
It is variously known as a pebble tool, pebble chopper, chopping tool, or simply as a chopper.
Artefacts on show range from the oldest - a 1.8 million-year-old chopping tool from Tanzania, to the newest - a Perspex sculpture created by a Maori artist and completed earlier this month, in time for the reopening.
One hundred objects have been selected from its unrivalled collections to illustrate the entire sweep of humanity's history: from a 2-million-year-old stone chopping tool, fashioned at a time when Homo sapiens did not even exist, to a solar-powered lamp, which McGregor optimistically casts as embodying the technology of tomorrow.
The oldest -- a two-million-year-old chopping tool made from stone found in the Olduvai Gorge in Tanzania -- was "the beginning of the toolbox," Mr. MacGregor said.
You might get them started, however, by telling them about the oldest object chosen by the British Museum: a two-million-year-old chopping tool made from stone found in the Olduvai Gorge in Tanzania that the museum's director calls "the beginning of the toolbox".
Mr. MacGregor credits the hand ax, being a more portable and flexible utensil than the chopping tool of yore, with helping humanity spread from Africa to Europe and Asia.
If you were trying to name the greatest invention in human history, it would be hard to beat the stone chopping tool and the hand ax.
The chopping tool, Mr. MacGregor writes, "represents the moment at which we became distinctly smarter, with an impulse not just to make things but to imagine how we could make things 'better.' " Exhibit B is even better: an Acheulean, or mid-Paleolithic, hand ax that dates back about 1.3 million years, when cooking had become the norm.
Hack the bark away from the sap (live) wood about 3 foot (0.9 m) above the ground, and about 10 inches (25.4 cm) wide, by chopping the bark away with your machete, hatchet, or other chopping tool.
