[killjoywashere]

> The UCSF group hypothesizes that this elevated level of orexin expression partially explains reduced sleep

So, one possible line of investigation would be a table of mammals, their sleep cycles, their orexin levels, and the numbers of copies of orexin and it's regulators in their genomes. For example: compared to humans, elephants have a lower cancer risk. Turns out they have significantly more copies of p53, a tumor supressor gene (1).

Perhaps a similar, somewhat parallel construct exists: elephants sleep 3-4 hours a night. Maybe they have more orexin? Maybe they have different copy numbers or mutations of the relevant genes in the pathway?

(1) https://pmc.ncbi.nlm.nih.gov/articles/PMC5061548/