Whoever says, "men are all alike," might also be able to say this about modern domestic stallions. According to new Y chromosome-specific DNA research on ancient horses, stallions were far more genetically diverse before humans domesticated them.

By sequencing DNA base pairs of the equine Y chromosome–the "sex chromosome" that is found only in males–geneticists have discovered that today’s stallions have a surprising lack of diversity compared to many other species and to ancient wild horses. Because Y chromosomes are passed from sire to colt and never to fillies, the research provides an interesting view into paternal-line equine evolution over hundreds of years of domestication and breeding practices, according to Sebastian Lippold, PhD, researcher at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.

This revelation provides a previously unseen view of the scientific and cultural history of the horse.

"It shows how breeding practices could influence and shape genetic diversity and how different this can be between males and females," Lippold said.

In the pilot study on ancient Y chromosome sequencing in a population of any species, Lippold and his team studied DNA samples from the remains of horses living thousands of years ago (the oldest dating to more than 47,000 years) and compared these same sequences of codes for each Y chromosome. The team found that these codes in horses were incredibly diverse compared to modern stallions’ DNA. Lippold based his findings on the results of a 2004 Swedish study that showed a particular DNA sequence in t