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U niversity of Otago research has shown that the ratio of male cancer risk is higher in populations descended from plough-using societies. The research, conducted by Professor David Fielding from the Department of Economics, looked at societies where the plough was adopted in the Neolithic period. The period is considered to be between 10,000BC and around 4,000BC, though experts still disagree on when the period came to an end and the Bronze Age began.

The effect “remained even after [looking at] socio-economic factors, including sex differences in epidemiological factors that are associated with higher cancer risk” said Fielding.

“One plausible evolutionary mechanism is that plough agriculture, which is more taxing than activities such as hoeing, created an economic environment which favoured those males who possessed greater upper-body strength.”

In societies where the plough was adopted, as opposed to the less labour-intensive method of hoeing, “males with genetic predispositions for higher testosterone levels would be able to out-compete other men by developing and maintaining stronger physiques.” The downside for the descendants of these males is that higher testosterone levels are also linked to a “higher risk of many types of cancer.”

Indeed, “countries where males and females were generally descended from non-plough societies would have a smaller difference in cancer rates between the sexes, because there was less selective pressure in those societies towards higher-testosterone males.”

Fielding compares this human evolutionary process, “if it did indeed take place, to the spread of a gene mutation in Neolithic dairy farming peoples that extended lactose tolerance beyond childhood.”

His research was not for medical purposes; “however, it adds to the evidence [that there is] a strong link between testosterone and different kinds of cancers.” For some types of cancers, this is already well known. Fielding said “testosterone levels [are] already part of the therapy for some types of cancer.” This includes prostate cancer. He did add that, for students, “cancer of this type is something [they are] not going to worry about for the next 30–40 years.”

The study is set to appear in the March issue of the Oxford University Press journal, Social Forces.