Most animals, including people, are diploid: two sets of chromosomes, one from each parent. Many plants, however, commonly carry more than two sets. This condition — called polyploidy — is a whole-genome duplication that places extra copies of every gene into each cell. Strawberries, for example, have eight sets of chromosomes, and many banana species are polyploid as well.
At first glance polyploidy looks risky. Doubling a genome can interfere with normal cell division, increase the chance of harmful mutations, and make it harder for a lineage to compete with slimmer, more streamlined relatives. That tension — why so many plant species are polyploid if the trait can be disadvantageous — has long been called the polyploidy paradox.
A new analysis led by plant biologist Yves Van de Peer at Ghent University offers a resolution. The team examined 470 sequenced flowering-plant genomes and searched each for genetic evidence of ancient whole-genome duplications. Using the fossil record to calibrate timing, they tracked when those duplication events happened over roughly the last 150 million years. What emerged was not a random scatter of events but distinct clusters: bursts of genome doubling that coincided with periods of major environmental upheaval, like dramatic warming or cooling and times of mass extinction.
One striking cluster dates to about 66 million years ago, the era of the asteroid impact that darkened the skies and wiped out many plant lineages along with the dinosaurs. Polyploid plants were overrepresented among survivors. That suggests that despite their typical disadvantages, plants with extra chromosome sets can sometimes gain a survival edge during extreme stress.
Why would extra genomes help during catastrophe? Having multiple copies of genes provides redundancy and flexibility. When conditions suddenly change — reduced light after an impact, or prolonged shifts in temperature — polyploid plants may be better able to adjust metabolism, tolerate stress, or maintain photosynthesis because they have additional gene variants and regulatory options. In that sense polyploidy acts like an evolutionary insurance policy: most of the time polyploid lineages perish, but in rare, turbulent intervals they prosper and seed new diversity. Over subsequent evolution, many descendants lose extra chromosome copies but retain molecular footprints of those ancient duplications.
The study’s findings help explain why polyploidy is common in modern plants despite being a risky mutation. Genome duplication events appear to be clustered at moments when environmental change opens up ecological space for lineages with unusual genetic toolkits. They also have practical implications. Plant breeders and biotechnologists may harness polyploidy to develop crops with greater resilience to stresses such as temperature extremes, drought, or low light — conditions becoming more frequent under contemporary climate change.
In short, whole-genome duplication is a double-edged sword: it can reduce fitness in stable times but become a decisive advantage when the world is thrown into upheaval. The new work suggests that polyploidy has repeatedly helped plants survive and diversify through some of Earth’s most turbulent chapters, offering both an explanation for a long-standing evolutionary puzzle and a potential resource for future agriculture.