Great white sharks hold a baffling genetic puzzle: uniform nuclear DNA but divided mitochondrial DNA that defies migration and evolution theories.
- White sharks show a striking mismatch between the DNA inside their cell nuclei and the DNA within their mitochondria. For years, scientists believed this could be explained by the way great whites migrate.
- A new study tested this idea by examining genetic differences across white shark populations worldwide. The evidence revealed that about 10,000 years ago, at the end of the last ice age, all great whites were confined to a single population in the Indo-Pacific Ocean. From there, they gradually spread to oceans across the globe.
- These results overturn the long-standing migration theory. Yet the true cause of the DNA discrepancy is still unknown, leaving researchers with a mystery to solve
- Last Ice Age Squeezed Great White Shark Populations
- During the last ice age, white sharks (Carcharodon carcharias) came dangerously close to disappearing. With sea levels far lower than they are now, their available habitat shrank, leaving little room for survival. When the ice age ended about 10,000 years ago, Earth began to warm, glaciers retreated, and oceans rose again. For great whites, these changes meant more space to roam and a chance at recovery.
- A study published in the Proceedings of the National Academy of Sciences found that during this period, white sharks had dwindled to a single, genetically mixed population located in the southern Indo-Pacific Ocean. Around 7,000 years ago, genetic differences began to appear, indicating that this population eventually split into two or more separate groups.
