Obituary: Professor Gerald Lincoln, leading endocrinologist and naturalist, born in Norfolk in April 1945, died at Puddledub in Fife on July 15th 2020 after a short illness.

Lincoln was a considerable polymath, who devoted his remarkable life to unravelling the mysteries of nature. His father, a Norfolk tenant farmer, died when he was six and the family had to leave the farm. His mother and her brother then bought a farm near Reepham, where he spent his childhood years running through the countryside and marvelling at the birds and especially the moths. He became an adept poacher too, carrying toilet paper as an alibi when he ventured off the road and into the woods.

With his older brother Dennis, Gerald started trapping and recording moths, a project that won him the Prince Philip Award for Zoology and led to a place at Imperial College, London studying zoology. It was at this time that he met his future wife, Caroline.

Roger Short working at the veterinary school at Cambridge had read about Gerald’s moth project in the newspapers and invited him to study the deer on the Isle of Rum for a PhD. His work led to a clear understanding of the way in which the red deer breeding cycle, including antler growth, is controlled by daylength to ensure that the hinds calve at the optimum time to benefit from spring grass. The breeding season in red deer is short and sharp; in effect they undergo an annual puberty.

It was while working from Rum that he noticed that his beard growth increased whenever he anticipated leaving the island and going to see his girlfriend. Beard growth reflects testosterone levels so in the true spirit of investigation he weighed his beard shavings daily to demonstrate the phenomenon. This was an important observation showing that testosterone levels are controlled by the higher centres. The results were published in a famously anonymous paper in Nature - a very rare distinction.

In 1974 Roger Short became Director of the new MRC Unit of Reproductive Biology in Edinburgh and Lincoln joined the Unit. This left him a year during which he, Caroline and two friends, travelled overland to Komodo to see the famous dragons. This expedition lasted twelve months and included a hair raising episode during which they were becalmed in a small native boat for several days.

On a subsequent trip to Australia he was diagnosed with acute leukaemia and flown home to the Royal Infirmary of Edinburgh with a prognosis of only a few weeks, however pioneering treatment was astonishingly successful and he went into remission for over forty years.

His work at the MRC unit used Soay rams which he kept in artificial daylight conditions. From this, he was able to elucidate the mechanism by which mammals decode photoperiod via changes in melatonin acting at the level of the pituitary gland - just below the brain. The pituitary reads the length of the nights - short in summer and long in winter creating two states of body and mind - one for summer and one for winter.

By measuring the frequency with which his rams hit their heads against the sides of the pens he created an index of ‘irritability’ and demonstrated that, counterintuitively, this increased as testosterone levels fell. From this he postulated a ‘male irritability syndrome’ pointing out that grumpiness in men coincides with the decline in testosterone with age; a theory that attracted widespread publicity. His infectious laughter whilst explaining this to an apparently uncomprehending John Humphrys on the BBC Today programme made wonderful broadcasting.

Over a 40-year career, Gerald unravelled the timing mechanisms that drive fertility and growth, concepts he later revealed as evolutionarily conserved mechanisms driving rhythms of life for all animal species on our planet. Recently he explained how unicellular marine microorganisms, which live for only a few days, have nevertheless annual rhythms enabling them to make yearly migrations. He pointed out that each human cell has similar annual clocks.

For his work, he received numerous scientific awards and medals, election to fellowship of the Royal Society of Edinburgh and appointment as Emeritus Professor of Biological Timing at Edinburgh University.

Throughout their time at Edinburgh, Gerald and Caroline based themselves at Kirkton Cottages, Puddledub in Fife, transforming two farm cottages and the surrounding grass paddocks into what was to become a paradise of biodiversity and a nature reserve. In retirement Gerald was able to devote himself to this work. The paths he constructed took visitors on an idiosyncratic journey past his ‘henge’, meticulously laid out to demonstrate the annual movement of the sun, and beside ponds and islands and established woodland that he had developed over many years. He encouraged everyone to his private reserve infecting them with his passionate and cheerful enthusiasm. He constructed a sand martin colony which each year bred over 400 fledglings, he attracted a pair of mute swans whose breeding performance was minutely recorded, and crucially he recorded moths all over Scotland often publishing his observations. His expertise in identifying moths led to work as a moth recorder for Scottish Natural Heritage and other bodies. Moths provide a means of measuring environmental change and Lincoln came to see very clearly the gravity of the damage to our environment. As 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 wild flowers - a crisis’.

He leaves his wife Caroline, two sons, Richard and Robbie, and a daughter, Rachel.