She explained the love of ginger hair among the Scots through a formula - genetic mutation + bad weather = red heads.
And said that the formula "was speculation rather than scientific study, but it is plausible."
It has been observed that while redheads amount to 1-2 per cent of the European population, an estimated 8 per cent of Scots and Irish are ginger.
Although human beings probably evolved in Africa 1 million to 2 million years ago, red hair appeared only once they had settled in Europe, possibly as recently as 20,000 years ago.
Ms Pritchard's explanation of this trait is based on well-established scientific theory.
Its foundation is the premise that ginger hair is genetically less advantageous because redheads have fair skin and are more prone to sunburn and skin cancer - unhelpful characteristics in hunter-gatherer societies.
In large populations in sunny climates, the ginger strain would tend to die out.
However, in Ancient Europe, small tribes broke away from bigger societies, and moved north and westwards, into areas where summers were shorter and winters longer.
The smaller groups ended up forming genetic bottlenecks-small gene pools in which chance mutations such as red hair were able to come to the fore.
There is complex genetics behind red and blond.
For example, one of the main genes for hair colour has 40 variants - but only about six cause red hair. People must inherit two of these six genes - one from each parent - to have red hair.
But the chances of this are always small, and thus there are so few redheads.
The best chance occurs in stable rural communities with a common ancestry - where people carrying the genes are likely to meet and have children.
"The smaller your sample the more likely something rare is going to happen," Times Online quoted Pritchard, 26, a student at the MRC Human Genetics Unit at the Western General Hospital, as saying.
"The Celts, by chance, had a high frequency of the ginger mutation, which was able to persist over time," she added.