The earliest evidence that archaeologists have for the domestication of dogs dates to around 40,000 years ago.  In that time, humans and dogs have developed a culture of relationship, meaning that we’ve come to understand the other’s needs and make an effort to help the other.  This video is an example of how deep that bond runs.

http://adventureblog.nationalgeographic.com/2015/06/09/video-denali-a-story-of-friendship-love-and-cancer/?utm_source=NatGeocom&utm_medium=Email&utm_content=pom_20150628&utm_campaign=ContentDogs