Credit: Yale Univ.
Elisabeth Vrba’s meticulous studies of fossil and living mammals challenged the conventional view of evolution. Instead of a process of slow, continuous adaptive changes driven by natural selection, she linked episodes of rapid species extinction and formation to cataclysmic events in the environment. She is best known as a rigorous and creative contributor to the development of macroevolutionary theory — the origin and evolutionary fates of species and higher groups. She has died aged 82.
Vrba was born in Hamburg, Germany. After the death of her father, her family moved to a sheep farm in South West Africa (now Namibia) in 1944. She received her PhD in zoology and palaeontology at the University of Cape Town, South Africa, in 1974, with her research focusing on fossil bovids. In 1969, she began working at the Transvaal Museum, Pretoria, rising to be its deputy director from 1977 to 1986.
Vrba exploded onto the scientific world stage at a macroevolution meeting in Chicago, Illinois, in 1980. Until then, she was mostly unknown to US palaeontologists. A draft of her provocative paper on how life evolved (E. S. Vrba S. Afr. J. Sci. 76, 61–84; 1980), which was sent to me and at least one other researcher in the United States, prompted me — as a co-organizer — to invite her to speak. As she put it, she was “armed with the brand of punctuated equilibria here espoused”.
The theory of punctuated equilibria had been proposed by me and Stephen Jay Gould in 1972. We argued that most species in the fossil record remain unchanged for long periods, with occasional branching events involving rapid change during which new species evolve.
Vrba found a way to squeeze insight from the barren lines of phylogenetic diagrams into our understanding of evolutionary processes. Focusing on fossil antelopes, she contrasted two evolutionary lineages. One, impalas, has had only two species in the past six million years, since the Miocene. The other, wildebeests, hartebeests and others, has contained at least 27 species in the same time span.
Estella Bergere Leopold (1927–2024), passionate environmentalist who traced changing ecosystems
Impalas exploit a wide range of ecological conditions, whereas the wildebeest lineage contains numerous grassland specialists. Vrba argued that the width of the niche that a species can occupy drives rates of both speciation and extinction, with the environment being the main force underlying this evolution. Her ‘effect hypothesis’ proposed that apparent directional trends in evolution are accumulations of increasing specialization inside lineages of narrow-niched species — a phenomenon she later referred to as species sorting — and are not necessarily manifestations of species selection.
By the time she addressed the macroevolution meeting, the conference had developed into a referendum on punctuated equilibria — and she quickly became the star of the show. The science writer Roger Lewin highlighted her work, including two figures from her 1980 paper, along with an image of Charles Darwin, as illustrative aids in his five-page review of the event in Science (R. Lewin Science 210, 883–887; 1980), which he described as “one of the most important conferences on evolutionary biology for more than 30 years”.
‘Exaptation’ is another original Vrba concept. An exaptation is a trait that has been co-opted to serve an extra function unrelated to that for which it originally evolved. For example, the wings of the African black heron (Egretta ardesiaca) are used not only for flight, but also to form an umbrella, casting a shadow over shallow water, where fish tend to congregate and be easy prey. The concept has captured the imaginations of many evolutionary biologists.
