Gerald Lincoln obituary

My friend Gerald Lincoln, the endocrinologist and naturalist who has died aged 75, devoted his life to unravelling the mysteries of nature.

Brought up on a farm in Norfolk – the son of Gertrude (nee Holmes), a geography teacher, and Ernest Lincoln, a tenant farmer – he spent his childhood in the countryside, marvelling at wildlife. He also became an adept poacher, carrying toilet paper as an alibi when he ventured into the woods.

He went to Brackendale school for boys, Norwich, then Fakenham grammar for his A levels. A moth recording project won him the Prince Philip award and led him to Imperial College London, to study zoology. There he met his future wife, Caroline Patterson, a law student at University College London.

A PhD at Cambridge University led to him studying deer on the Isle of Rum, off the west coast of Scotland. He explained how the red deer breeding cycle is controlled by day length, to ensure that hinds synchronise their calving to benefit from spring grass. Their breeding season is short and sharp; in effect they undergo annual puberty.

He noticed his beard growth increased whenever he anticipated leaving the island and going to see his girlfriend, and by weighing his shavings daily he proved the phenomenon; an important observation showing that testosterone levels are controlled by the higher centres, which was published in a rare anonymous paper in Nature in 1968.

In 1974 Gerald joined the new MRC unit of reproductive biology in Edinburgh as principal investigator. Keeping Soay rams in artificial daylight, he showed how mammals decode photoperiod – the light period of the day – via changes in melatonin. The pituitary reads the length of the nights, creating two states of body and mind - one for summer and one for winter.

Measuring the frequency with which his rams hit the sides of the pens he demonstrated that, counterintuitively, their irritability increased as testosterone levels fell. He postulated a “male irritability syndrome”, pointing out that grumpiness in men coincides with declining testosterone. His infectious laughter whilst explaining this to an apparently uncomprehending John Humphrys on the BBC Today programme made for wonderful broadcasting.

Gerald unravelled the timing mechanisms driving rhythms of life for all animals including unicellular microorganisms that live for a few days yet nevertheless make yearly migrations. He pointed out that each human cell has similar annual clocks. He received numerous awards, was elected to fellowship of the Royal Society of Edinburgh in 1993 and in 2008 was appointed to a personal chair as professor of biological timing at Edinburgh University (made emeritus on his retirement in 2010).

Gerald and Caroline settled in the hamlet of Puddledub, Fife, creating a paradise of biodiversity at their home. Gerald encouraged visitors to their nature reserve, infecting them with enthusiasm. He built a sand martin colony, attracted mute swans to his ponds, and recorded moths. A few days before died, he wrote: “The alarm bells have gone off - industrial farming and the encroachment of towns is trashing the countryside. Gone are the butterflies and the wildflowers – a crisis.”

He is survived by Caroline, whom he married in 1972, two sons, Robert and Richard, and a daughter, Rachel, and a grandson, Brodie.