A boy's suitcase opened in Cincinnati in the 1950s, and out spilled a genetic revolution—ten European common wall lizards, smuggled home from a vacation in northern Italy, that would become hundreds of thousands, perhaps even millions, scampering across urban parks and neighborhoods in Ohio. These "Lazarus lizards," named after the boy's family who founded the Lazarus retail chain, arrived with every disadvantage: a minuscule founding population, genetic isolation, and the challenge of surviving in an unfamiliar continent. Yet they thrived with a kind of biological audacity that scientists are only now beginning to understand.
The secret, according to new research published in Molecular Ecology, had less to do with genetic strength than with sheer population momentum. Researchers from Ohio State University and Ohio Wesleyan University sequenced genomes from four different populations—samples from the original Italian source population, two Cincinnati populations collected in 2007 and 2022, and a surrogate population that emerged briefly in Columbus, Ohio in 2021. What they discovered upended conventional wisdom about how species survive genetic bottlenecks. The Cincinnati lizards experienced significant loss of genetic variation and a severe population dip after arrival, the kind of genetic damage that typically devastates a species. But the population grew so rapidly that it essentially outran its own inbreeding.
"They just grew so fast," explained H. Lisle Gibbs, professor emeritus of evolution, ecology and organismal biology at Ohio State. "If you think you have a bottleneck, but it doesn't last very long, then you don't have a bottleneck."
The Columbus population, which served as a modern parallel to the original 1951 introduction, showed the mechanism in action: intense inbreeding, high rates of genetic homozygosity that should have been catastrophic, and a dramatic population collapse followed by explosive growth. The same pattern appears to have played out in Cincinnati seventy years ago. The inbreeding that should have weakened the population never had time to matter. The lizards simply multiplied so voraciously that they overwhelmed the genetic damage.
This success story has a second act: adaptation. Researchers found genomic differences between the Italian and Cincinnati populations suggesting the lizards are evolving to fit their new home. Genes related to neural function hint at behavioral flexibility, while pathways involving learning and memory—mechanisms that in humans help counteract lead toxicity—show signs of selection pressure. This last detail is particularly striking. European common wall lizards in Cincinnati accumulate astronomically high levels of lead in their blood but show no symptoms of lead poisoning. Eric Gangloff, the study's co-author and an associate professor at Ohio Wesleyan University, is investigating this remarkable tolerance.
Climate and habitat, Gangloff notes, played a crucial role in the lizards' invasion. Milan and Cincinnati may seem worlds apart, but from a lizard's perspective they offer similar climates and urban structures. More importantly, the Cincinnati lizards faced no serious competitors. They landed in a vacuum and filled it completely.
What emerges is a portrait of a species succeeding not through genetic perfection but through demographic momentum—a reminder that evolution often rewards speed and abundance over fitness and refinement. The Lazarus lizards show that sometimes, the best way to overcome a genetic bottleneck is simply to grow faster than the bottleneck can constrain you.