Ernst Walter Mayr died on the 3rd of February 2005 at the age of 100; he was one of the 20th century’s leading evolutionary biologists.

He was also a renowned taxonomist, tropical explorer, ornithologist, and historian of science.

Born on the 5th of July 1904, he was the second son of Helene Pusinelli and Dr. Otto Mayr. His father was a jurist (District Prosecuting Attorney at Würzburg) but took an interest in natural history and took the children out on field trips.

He learnt all the local birds in Würzburg from his elder brother Otto. He also had access to a natural history magazine for amateurs, Kosmos. His father died just before he was thirteen.

On the 23rd of March 1923 on the lakes of Moritzburg, the Frauenteich, he spotted what he identified as a red-crested pochard.

The species had not been seen in Saxony since 1845 and the local club argued about the identity. Raimund Schelcher (1891–1979) of the club then suggested that Mayr visit his classmate Erwin Stresemann on his way to Greifswald, where Mayr was to begin his medical studies.

After a tough interrogation, Stresemann accepted and published the sighting as authentic. Stresemann was very impressed and suggested that, between semesters, Mayr could work as a volunteer in the ornithological section of the museum.

Mayr wrote about this event, “It was as if someone had given me the key to heaven.” He entered the University of Greifswald in 1923 and, according to Mayr himself, “took the medical curriculum (to satisfy a family tradition) but after only a year, he decided to leave medicine and enrolled at the Faculty of Biological Sciences.”

Mayr was endlessly interested in ornithology and “chose Greifswald at the Baltic for my studies for no other reason than that … it was situated in the ornithological most interesting area.”

Although he ostensibly planned to become a physician, he was “first and foremost an ornithologist.”

During the first semester break Stresemann gave him a test to identify tree creepers and Mayr was able to identify most of the specimens correctly.

Mayr joined the faculty of Harvard University in 1953, where he also served as director of the Museum of Comparative Zoology from 1961 to 1970.

It’s this isolation or separation that creates new species, said Mayr. The traits that evolve during the period of isolation are called “isolating mechanisms,” and they discourage the two populations from interbreeding.

He retired in 1975 as emeritus professor of zoology, showered with honors. Following his retirement, he went on to publish more than 200 articles, in a variety of journals—more than some reputable scientists publish in their entire careers; 14 of his 25 books were published after he was 65.

Even as a centenarian, he continued to write books. On his 100th birthday, he was interviewed by Scientific American magazine.

Mayr died on 3 February 2005 in his retirement home in Bedford, Massachusetts after a short illness.

His wife, Margarete, died in 1990. He was survived by two daughters, five grandchildren and 10 great-grandchildren.