The early orthodoxy had it that we "tool makers" simply wiped out Neanderthals with a combination of spear and fire-making, domestication of dogs etc. However, an emerging school argues that human and Neanderthal ancestors interbred, producing a transfer of genes in a species blend, rather than clean-cut extinction.

By 2003, the Human Genome Project had largely mapped the role of each of the 20,000 to 25,000-odd genes in our double helix. In 2008, researchers at the Max Planck Institute of Evolutionary Anthropology extracted and identified 60 per cent of the Neanderthal genome from bone fragments preserved in the Croatian Vindija Cave.

The researchers demonstrated that 1 per cent to 4 per cent of (non-African) human DNA comes from Neanderthals.

A tantalising question is which human traits do we owe to the legacy of that primaeval co-mingling? Neanderthals were concentrated in northern Europe and appear to have been largely, or exclusively, redheads. Two copies of the recessive gene on human chromosome 16 yields a classic helpful mutation. A defective protein (MC1R) on the plasma membrane allows a pale-skinned redhead to process more vitamin D with less sunlight - giving an evolutionary edge in cold climes to sun-starved Vikings, Celts and their northern European cousins. It also delivers higher pain thresholds.

The highest concentration of the gene combo is found in Scotland where fully 40 per cent of the population are carriers. However, in this respect, we need to recognise  that most of us are, in fact, part-Neanderthal.