The duo allowed leeches to feast on sheep's blood until they were full, measuring both the change in the length of their segments as they fed and the rate at which they spread as they crawled. (sciencemag.org)
So, the length of the segments your dog shares with her ancestors decreases with each generation above her: she shares longer segments with her mom than her grandma, longer segments with her grandma than her great - grandma, and so on. (my.embarkvet.com)
We can use the length of segments Aussie shares with our reference dogs to see how many generations it has been since they last shared an ancestor. (my.embarkvet.com)