Don’t only humans have the ability to use language and understand abstract concepts?
Some scientists have thought that the noises dolphins make may be a language, for many years now. There is also reserach into Prarie Dog language, whale song, and some of the noises other apes make to communicate. en.wikipedia.org/wiki/Animal_language
Only humans talk about abstract concepts, in a language other humans understand. 
Did you ever read any Terry Pratchett books? My favourite character is You B*stard, a camel who happens to be the greatest mathematician in the world. There isn’t much else to do in a desert… 
Seriously, if humans started thinking abstract concepts due having more time (the discovery of fire, the advent of farming…) perhaps other animals can or have develop this also. For example, those species of chimps living in communities, and household/farmed animals. I’ve heard pig farmers say that you occasionally get very pensive, intelligent pigs…
It depends on your definition for abstract concept. Use of language is also poorly defined, other species are definitely capable of communication.
I think only human can use language but I think not only human can understand…