This narrowed the fossil age approximation to 1.95–1.78 million years old, within what’s known as the Olduvai Subchron.
Apart from being a geological curiosity, the constant toing-and-froing of the Earth’s polarity has proven extraordinarily useful in pin-pointing the geological ages of rocks.
This is perhaps no better illustrated than in the recent – and incredibly precise – dating of the Australopithecus sediba remains from South Africa.
At the 2 million year mark, the crucial transition point when Australopithecus became Homo, few fossil remains existed. sediba individuals found at the Malapa cave site some 60 km northwest of Johannesburg met their demise at almost precisely this time.
In fact, the age estimate for the skeletons is 1.977 years old, give or take 2000 years – a remarkably precise approximation given their antiquity.