▁are ▁not ▁predict able , ▁similar ▁to ▁that ▁of ▁mixed - bre ed ▁dogs . ▁Gen etic ▁research ▁shows ▁that ▁w olf ▁and ▁dog ▁populations ▁initially ▁diver ged ▁approximately ▁ 1 4 , 0 0 0 ▁years ▁ago ▁and ▁have ▁inter bre d ▁only ▁occasionally ▁since , ▁account ing ▁for ▁the ▁dis similar ity ▁between ▁dogs ▁and ▁wol ves ▁in ▁behavior ▁and ▁appearance . ▁In ▁many ▁cases ▁the ▁resulting ▁adult ▁w olf dog ▁may ▁be ▁larger ▁than ▁either ▁of ▁its ▁parents ▁due ▁to ▁the ▁gen etic ▁phenomen on ▁of ▁heter osis ▁( comm only ▁known ▁as ▁hy brid ▁vig or ). ▁Bre eding ▁experiments ▁in ▁Germany ▁with ▁P ood les ▁and ▁wol ves , ▁and ▁later ▁on ▁with ▁the ▁resulting ▁w olf d ogs ▁showed ▁un rest rict ed ▁fert ility , ▁m ating ▁via ▁free ▁choice ▁and ▁no ▁significant ▁problems ▁of ▁communication ▁( even ▁after ▁a ▁few ▁gener ations ). ▁The ▁off spring ▁of ▁P ood les ▁with ▁either ▁co y otes ▁and ▁jack als , ▁however , ▁all ▁showed ▁a ▁decrease ▁in ▁fert ility , ▁significant ▁communication ▁problems , ▁and ▁an ▁increase ▁of ▁gen etic ▁dise ases ▁after ▁three ▁gener ations ▁of ▁inter bre eding ▁between ▁the ▁hy br ids . ▁The ▁research ers ▁therefore ▁concluded ▁that ▁domestic ▁dogs ▁and ▁wol ves ▁are ▁the ▁same ▁species . ▁ ▁Wolf d ogs ▁display ▁a ▁wide ▁variety ▁of ▁appearances , ▁r anging ▁from ▁a ▁res embl ance ▁to ▁dogs ▁without ▁w olf ▁blood ▁to ▁animals ▁that ▁are ▁often ▁mistaken ▁for ▁full - blo