The fossil record has revealed many hominin lineage branches during evolution, but only Homo sapiens survived to the present. Neanderthals and Denisovans, two extinct lineages, are our closest evolutionary relatives. While the fossil record can reveal information about their anatomy and lifestyle, it cannot provide information about how their brains develop. Phenotypic data is only possible from comparisons between humans and living primates, underscoring differences in brain development that have evolved since our last common ancestor around 6 million years ago [1]. However, recent evolutionary changes in brain development—such as those differentiating us from our extinct relatives, could not be studied due to the lack of soft tissue.

Ancient DNA sequencing has opened the door for comparative paleogenomics, providing the genetic information of our closest relatives. Most of the comparative genetics between archaic and modern humans has been on introgressed genomic sites [2]. These are regions in our genomes where modern humans have adopted archaic elements via ancestral interbreeding and admixture. While many research focuses have been on these introgressed sites’ clinical benefits and consequences, studying the sites where modern and archaic humans diverge can be of important clinical value.

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