A new study by international researchers has revealed that Neanderthals experienced a population crash around 75,000 years ago, which may have contributed to their extinction. The researchers found that almost all late Neanderthal in Europe were descendants of one small group. The study combined DNA analysis with existing archaeological evidence to explain how Ice Age conditions forced widespread groups to retreat to a single safe zone, or refugium, somewhere in southwestern France. The mitochondrial DNA (or mtDNA) was used to reconstruct ancient history, indicating a species that has repeatedly spread out and broken up into smaller groups, making them more vulnerable to natural disasters, environmental pressures, and low genetic diversity. The findings were published in PNAS.