Old ideas shimmy in flashy clothes

At the time of his death at the age of 100 in February, Ernst Mayr's scientific career had spanned nearly eight decades. He was one of a small group of highly influential "neo-Darwinian" evolutionary biologists of the 1930s to 1950s. Extraordinarily, he could refer to articles he wrote before the Second World War. This is his 25th and last book.

Mayr built his reputation on contributions he made while still relatively young. He recognised that Darwin had provided an explanation for variation among individuals via his mechanism of natural selection, but that natural selection alone could not explain why the biological world seemed to divide itself into discrete entities we call species. Mayr's "biological species concept" is perhaps what he is best remembered for, defining species as populations of potentially or actually interbreeding individuals unable to exchange genes with other such groups.

His complementary idea of "allopatric speciation" suggested that most new species arise when populations get geographically separated from one another. This work laid the foundations for decades of research by a new generation of scientists interested in the mechanisms that served to isolate populations, leading to the evolution of new species. The modern field of "mate recognitions systems" or how individuals recognise their own kind (for example, pheromones, plumage, behavioural displays - just think "perfume", "flashy clothes" and "disco dancing") is a good example, being a direct descendant of Mayr's ideas.

Ironically, his early successes may have been responsible for what eventually became a mixed reputation among evolutionary biologists. For some, he was the Darwin of the 21st century, but for others he became an anachronistic figure whose ideas had largely fossilised by the 1950s.

This book will do little to bring about a rapprochement between these two camps. At a time when biology is attracting unprecedented attention and grabbing headlines with research on cloning, the complete genomes of many organisms and finding genes that influence everything from personality to sexual preferences, Mayr devotes the first seven chapters to ageing questions of the philosophy of biology. He vigorously argues for the auton-omy of biology as a science and analyses Darwin's contributions to modern thought.

Later chapters return to several of Mayr's favourite topics, including natural selection and speciation. Two final chapters take up human evolution and the wondrous question of whether we are alone in the universe. The book's dust jacket promises that Mayr has a "highly original"

view of how humans evolved evolution. I could not find it: his views on this interesting topic being the conventional treatment of our evolution from the early Australopithecine and later Homo species with a bit of regional diversification thrown in. In the "Are we alone?" chapter, Mayr confidently asserts that it is obvious we are not. But for others, our uniqueness in the universe is a subtle question that continues to attract much interesting speculation on both sides.

Most of us bumble through life having opinions but forgetting precisely why we hold them. Mayr was impressive as someone who seemed never to forget his reasons. And yet his retentiveness may have been responsible for his declining influence in later years, preventing him from moving on. He never embraced the molecular revolution in biology, and this book scarcely casts a glance towards modern topics such as genomics.

What Makes Biology Unique? will appeal to the hard core of Mayr enthusiasts and give readers seeking a modern view of this vibrant field a last viewing of a prodigious and influential writer and thinker from an earlier era of biology.

Mark Pagel is professor of evolutionary biology, Reading University.