Professor Michael Majerus: Geneticist who defended Darwin in the battle against creationism

Michael Majerus was a gifted Cambridge scientist and teacher, and a doughty defender of Darwin and his theory of natural selection. Hissubjects were moths and ladybirds, which he saw as perfect tools fordigging into evolutionary questions, but he also loved them for their own sake. He was that increasingly rare phenomenon, a scientist who was also a field naturalist (he was running a moth trap in his garden from the age of 10). Perhaps it was this instinctive "feeling for the organism", allied to his natural vitality and infectious enthusiasm for insects, that made Majerus such a popular teacher, and one in demand by the media.

Majerus was internationally known in the fields of ecological and evolutionary genetics. His best-known work was on the Peppered Moth, whichhas two forms, one light and speckled, the other dark and sooty (knownas melanic), and has long been heldto be an example of evolution in action. The dark form predominates in polluted areas because it is less easilyspotted by birds when at rest ontrees. Stung by a review of his 1997 book, Melanism: Evolution in Action, which rejected the supporting evidence and so became grist to the mill of creationists, Majerus set about proving his case.

It took him seven years of meticulously planned experiments which tested and compared the predation of the moths by birds and bats by release and recapture, and of the respective behaviour of wild and lab-reared moths. He also redetermined exactly where the moths rest by day, a controversial part of the original research which had been criticised on the grounds that the moths never rested on tree trunks. Majerus proved the critics wrong: they do (it is just that they are hard to see). His work is seen as a significant contribution to the evolution versus creation/intelligent design debate, and has helped to swing the international scientific consensus back in favour of the Peppered Moth as a supreme and easily understood example of evolution.

Majerus's other lifelong passion was for ladybirds. His work focused onthe role of sex in evolution. He wasthe first to show that the femalebeetle's mating preferences couldbe genetically determined, thereby confirming a critical aspect of Darwin's theory of sexual selection by female choice. He also worked extensively on "male-killing bacteria"which reduce the number of male ladybirds and have evolutionary consequences in the way that it distorts their behaviour.

Majerus established a system for recording British ladybird species, and encouraged as many people as possible, including children, to join in. Hence Britain was well placed to monitor the invasion of the non-native Harlequin Ladybird in 2004 and its steady advance over much of England. For a while Majerus was omnipresent in the media, which he much enjoyed. He was, however, pessimistic about the likely ecological consequences of the invasion, believing, with good reason, that it would result in reduced numbers of native ladybirds.

Michael Majerus (known to his friends as "Mike") was born in the old county of Middlesex in 1954, the second of three brothers. His father, Fernand, was a Luxembourg national who met his wife, Muriel, in Britain and remained to build a successful family textile business. Mike's love affair with insects probably began at the age of four, when he acquired his first butterfly net, and was strengthened six years later with the present of a moth trap. His parents encouraged him, his mother taking him on weekend mothing expeditions to the New Forest, while his father brought back specimens from his travels to the Far East and Australia. One Christmas coincided with the emergence of his captive Indian Moon Moths which he remembers hanging motionless on the Christmas tree like live decorations.

He was educated at Merchant Taylors' School in London and graduated in botany and zoology at Royal Holloway College, London. He went on to study for his doctorate at the college, choosing as his subject the genetic control of larval colour in the Angle Shades moth. After a brief sojourn as a research demonstrator at Keele University, he began his career-long association with Cambridge in 1980, starting as a research associate in the Department of Genetics, then moving steadily up the academic ladder as demonstrator, lecturer and finally Reader in Evolution. In 2006 he was made Professor of Evolution. From 1991, Majerus was also a Teaching Fellow of Clare College.

Majerus was the author of several books, including Sex Wars: Genes, Bacteria and Biased Sex Ratios (2003) and Ladybirds (1994) and Moths (2002) in the Collins New Naturalist series, both of which successfully combine natural history with accessible experimental science, including his own. His work took him all over the world, fromarctic Lapland to tropical Africa, where Majerus would combine academic conferences and research with expeditions with a butterfly net. He saw his collection as part of his research record on defensive colour patterns, reproductive strategies and genetic variation.

With Mike Majerus the boundaries between life and work, teaching and research, were more than usually blurred. He was a tireless advocate of evolution and always eager to communicate with the widest possible audience, including children. From 2006 he was president of the Amateur Entomologists' Society, and in the same year received the British Naturalist's Association's Sir Peter Scott Memorial Award for his contributions to British natural history.

Majerus was probably happiest when he was trekking through a rainforest, or climbing some mountain, and took great pleasure in sharing these experiences with his students (who will also remember the musicof Genesis, which was played non-stop all the way to his fieldwork sites). "Iam getting old," he said in a recent and memorable lecture on the Peppered Moth controversy (he was 53),"and have spent my life in scientific enquiry and discovery. And it has been a great life."

Peter Marren

Michael Eugene Nicolas Majerus, ecological geneticist: born London 13 February 1954; Postdoctoral Research Associate, Dept of Genetics, University of Cambridge, 1980-87; University Lecturer, 1987-2001; Teaching Fellow, Clare College, 1991-2009, Reader in Evolution, 2001-2009, Professor of Evolution, 2006-2009; Fellow of the Royal Entomological Society; President, Amateur Entomologists' Society (2006-09); married 1979 Vicki Maclean (marriage dissolved), 1988 Tamsin Harris (two sons, one daughter, marriage dissolved), 2005 Christina Poole; died Coton, Cambridgeshire 27 January 2009.