Early to bed, early to rise might mean you are part Neanderthal

A new study suggests that genetic materials from our Neanderthal ancestors may be responsible for our habit of waking up early. For the results, published in the journal Genome Biology and Evolution on December 14, researchers combined the ancient DNA of Neanderthals, large-scale genetic studies in modern humans, and artificial intelligence for the study. 

Experts often study the archaeological evidence of Neanderthals and learn about their life and our history. Scientists have previously established that around 700,000 years ago, our lineages split apart, most likely in Africa. 

The modern humans largely stayed in Africa and the Neanderthal lineage migrated into Eurasia, where they encountered diverse new environments. 

They experienced higher latitudes with greater seasonal variation in daylight and temperature — all of it impacted their way of living. 

The population split in two about 400,000 years ago with hominins spreading west becoming Neanderthals and their cousins to the east becoming a group known as Denisovans. 

Former studies have found that the two groups lived for hundreds of thousands of years, but about 40,000 years ago, they disappeared from the fossil record.  

By then, modern humans had expanded out of Africa, sometimes even interbreeding with Neanderthals and Denisovans. And the fragments of their DNA can be found in most living humans even today. 

Now, a team of researchers at Vanderbilt University, the University of Pennsylvania, and the University of California San Francisco studied genetic data from a catalogue of hundreds of thousands of people in the United Kingdom. 

For the study, they performed a genome-wide association study (GWAS) to look for traits linked to the habit of waking up early in the morning. 

Notably, the process of GWAS helps scientists to identify genes associated with a particular disease, or another trait. 

Earlier, the experts have noted that this particular method studies the entire set of DNA of a large group of people, searching for small variations, called single nucleotide polymorphisms or SNPs. 

The researchers have inferred differences in circadian gene sequences, splicing, and regulation between archaic hominins and modern humans. 

They identified 28 circadian genes containing variants with the potential to alter splicing in archaics and 16 circadian genes likely divergently regulated between present-day humans and archaic hominins. 

The study said, "These differences suggest the potential for introgression to modify circadian gene expression." 

The study has compared associations to the genomes derived from three ancient hominins, which have been previously published by scientists. 

The genomes have been derived from a 120,000-year-old Neanderthal, a 72,000-year-old Denisovan found in the mountains of Mongolia, and a 52,000-year-old Neanderthal from modern-day Croatia. 

The researchers have found that many introgressed variants with effects on sleep preference. They found that these variants consistently increase "morningness". The study indicated a directional effect on the trait, and it is also consistent with adaptations to high latitudes observed in other animals. 

Lead author John A Capra from the University of California at San Francisco, said, "By analysing the bits of Neanderthal DNA that remain in modern human genomes we discovered a striking trend: many of them have effects on the control of circadian genes in modern humans and these effects are predominantly in a consistent direction of increasing propensity to be a morning person." 

"This change is consistent with the effects of living at higher latitudes on the circadian clocks of animals and likely enables more rapid alignment of the circadian clock with changing seasonal light patterns," Capra added.