Founder’s Briefs: An occasional series where Mongabay’s founder Rhett Ayers Butler shares analysis, perspectives, and story summaries.

Elisabeth Vrba did not set out to overturn the way scientists understood evolution. But her relentless inquiry, guided by a keen mathematical mind and a sharp eye for patterns in the fossil record, challenged some of Darwin’s most sacrosanct ideas. In a field where slow, incremental change had long been the reigning orthodoxy, she made the case that evolution moved in bursts — abrupt waves of extinction and speciation triggered by climatic upheaval. Her “Turnover Pulse” hypothesis became one of the most influential, and contentious, contributions to evolutionary biology in the past half-century.

Born in Hamburg, she moved to what is now Namibia as a child. The stark landscapes of her new home seemed an apt setting for the questions that would later define her career. She studied zoology and mathematical statistics before turning her focus to fossil antelopes, which provided the raw material for her boldest ideas.

Vrba’s great insight was that extinctions and originations of species were not random, nor the result of gradual competition between individuals, as Darwin had proposed. Rather, they were shaped by environmental changes, particularly shifts in climate. She noticed that some lineages remained remarkably stable, while others proliferated in fits and starts. The difference, she argued, was in their ecological flexibility. Generalists, with broad diets and adaptable habits, could ride out environmental changes. Specialists, attuned to narrow ecological niches, were more vulnerable — flourishing in one era, vanishing in the next.

Her ideas were met with skepticism. Punctuated equilibrium, proposed in 1972 by paleontologists Niles Eldredge and Stephen Jay Gould, had already shaken up evolutionary biology by suggesting that species changed little for long periods before rapidly branching into new forms. But Vrba’s work went further. She suggested that external forces, rather than internal biological pressures, were the primary drivers of these bursts of change.

Vrba’s work also shaped thinking on exaptation — the process by which traits evolve for one function but are later co-opted for another. She pointed out that many features in organisms, from feathers to mammalian ear bones, were repurposed from ancestral structures rather than designed from scratch by evolution.

Though not as widely known as some of her contemporaries, her impact was profound. She infused paleontology with a rigor that brought it closer to the predictive precision of other sciences, demanding that hypotheses be tested with quantitative methods rather than merely asserted from anecdotal evidence.

For Vrba, the fossil record was not a static archive of long-dead creatures, but a dynamic record of nature’s upheavals — a story written in deep time, waiting to be read by those who knew where to look. She never claimed that her hypotheses provided all the answers, only that they asked better questions. In doing so, she changed the course of evolutionary science.

Banner image:Elisabeth Vrba. Photo by J Play.