Research conducted by belyaev and trut has shown that foxes can be domesticated over the course of many generations, by and mating animals with certain traits (e. g., responses to feeding, handling,

The given blank can be filled with selecting.  

It has been shown by Belyaev and Trut that foxes can be domesticated, over the time of various generations, by selecting and mating animals with certain traits, like responses to feeding, handling, and others.  

A sustained multi-generational association in which one group of species presumes a substantial extent of effect over the care and reproduction of another group to secure a more predictable supply of resources from that latter group is known as domestication.  

layer 3 is younger than layer 6.

radon is correct hope this