Most scientists believe that the first modern humans emerged around 150,000 years ago, somewhere in East or southern Africa, and from there spread slowly out to colonise the entire planet. Ever since the remarkable Kenyan discoveries by the Leakeys in the 1920s, Africa has become a hotspot for studying human origins. Inevitably the press has sought to glamorise important discoveries by personalising the issues - hence the emergence of the "archaeo-celebs", the most famous being Eve.

She was not the first. Before her appearance in 1987 two other ladies provoked a distinct flutter of interest. In 1947, at Sterkfontein in the Transvaal, Broom and Robertson discovered the remains of Mrs Ples, an upright-walking hominid over three million years old. Amid fierce controversy she was proposed as the "missing link" between humans and apes.

Next the spotlight fell on Lucy, whose largely intact skeleton was found by Johanson and Gray in Kenya in 1974. Her apparently upright posture, more than four million years ago, again challenged the textbooks.

But her inflexible wrist joints betrayed her need to walk with forearm assistance and she too, after much debate, was classified along with Mrs Ples as a mere australopithecine.

When Eve was announced, in January 1987, excitement again ran high. Here at last, the name suggested, was "the single mother of mankind". Creationists were triumphant. True, Eden appeared to have relocated to Africa and, disappointingly, 145,000bc was not quite the Biblically predicated 4004bc. What many failed to notice, however, was that Eve is not a "real-world" Lucy or Mrs Ples, but a scientific concept.

She was derived by analysing the mitochondrial DNA of women across the planet. This particular genetic marker passes little changed from mother to daughter, generation after generation. Since with every step back in time there are fewer and fewer women, you finally arrive at a single individual.

The ticking of the mitochondrial clock places that person as having lived around 147,000 years ago - just the sort of date the fossil record implies. No less conclusively, patterns in the planet-wide genetic data converge to indicate a common human origin in sub-Saharan Africa.

Some eight years later Adam, too, was identified by a similar process of retro-analysis, this time using the male-only Y-chromosome. His trail leads back only 63,000 years, but again the data point unmistakably to an African source.

Of course these genetic constructs are not our "first parents". While Eve was alive she could hardly have been the sole female around, though she may well have been part of a very small group. All the mitochondria tell us is that only her strain survived. Her sisters' mitochondria eventually died out, just like an ancient family name will if there are no sons born directly in the line.

The real significance of "Eve" is that she, like "Adam", is African. Africa, it seems, truly is the cradle of mankind.