A recent scientific investigation into the genetic lineage of modern humans and Neanderthals indicates that both groups split from a common ancestor around 600,000 years ago. As modern humans migrated from Africa, they encountered Neanderthals, particularly during a notable exodus 60,000 years ago, leading to extensive hybridization between the two groups. Although Neanderthals went extinct about 40,000 years ago, remnants of their DNA persist in contemporary non-African genomes, accounting for approximately 2% of their genetic material.

Intriguingly, modern human genomes contain regions referred to as 'Neanderthal deserts,' where Neanderthal genetic material is scarce or entirely absent. This phenomenon is particularly pronounced on the X chromosome, which contains minimal Neanderthal traces. Scientists have proposed two main hypotheses for this observation. The first hypothesis suggests that natural selection eliminated Neanderthal genes from the X chromosome because they were biologically incompatible with modern humans; though later studies showed a significant mixture of modern human genes in Neanderthal X chromosomes, weakening this explanation.

The second hypothesis posits that interbreeding predominantly occurred between Neanderthal males and modern human females, resulting in very little Neanderthal X chromosome DNA entering contemporary human populations. Since females have two X chromosomes while males only have one, when the breeding combinations were Neanderthal males and modern human females, only daughters could inherit the Neanderthal X chromosome, thereby limiting the amount of Neanderthal X chromosome genes passed down to modern humans. This study sheds light on the complexities of human evolution and the intermingling of different hominin species, significantly enhancing our understanding of human ancestry.