Filming Icelandic Horses Swimming from Underwater

 Here's a great video of the leg action of Icelandic horses filmed by scuba divers.  It looks most of them are tolting.  I wonder if there is any efficiency to tolting while swimming or each horse has an individual preference?

 

Origin of DMRT3 the Gaited Gene--6000 years ago?

Ancient Chinese horse performing
flying pace

In 2016, a study reported that the earliest finding of DMRT3, indicating gaitedness or ability to rack or tolt, was in York, England around 850 AD.  Since that time, there have numerous articles crediting the Norse of selecting gaited horses from England and moving them to Iceland and spreading the DMRT3 gene across the Europe and then the world.

The original study did not include the many historic, genetic samples from Asia and across the world.  It did not consider the pre-850 AD written descriptions of gaited horses in Greek and cuneiform and the numerous artistic representation of horses ambling in ancient Egypt and Roman times.

Staiger et al published "The evolutionary history of the DMRT# 'Gait keeper' haplotype in 2017.  This study compared genetic sequences of DMRT3 across 26 breeds to estimate how long it would have taken for the haplotypes to change.  "We used the pattern of sequence variation int he DMRT3 region to explore the evolutionary history of the haplotypes."

"The low sequence diversity among mutant chromosomes demonstrated that they must have diverged from a common ancestral sequence within the last 10 000 years. Thus, the mutation occurred either just before domestication or more likely some time after domestication and then spread across the world as a result of selection on locomotion traits."

In other words, it is likely that the mutation for gaitedness occurred sometime after the domestication of the horse from 6000 to 10000 years ago.  

No conclusive evidence was found about the geographic origin of the gene.  "For instance, the mutation could have been spread widely via the military exploits of Alexander the Great (3rd century BC), Attila (5th century) and Ghengis Khan (13th century). Furthermore, the Romans, and their use of Greek horses, could have helped spread the mutation throughout Europe and the Middle East (Antikas 2015)."

Source:  https://onlinelibrary.wiley.com/doi/full/10.1111/age.12580