Going from a wolf to a pug... given enough time you could breed that to something more akin to a rodent, then to something like an otter, back to something like a seal, to a dolphin... hey presto, land based mammal to marine based mammal. Doing that would take a long time though. This is why microbial life is often used as an example in action because it can reproduce quick enough to see big changes.
To go back to our nearest ancestor... I think the example used was your mother holding her mother's hand and she her mothers... you'd have to have 23 miles of mothers lined up hand in hand before you got to an area where homo sapien and homo erectus or whatever the direct ancestor start blurring (which is the important bit - going from species to species is a slow blur not a chicken and egg thing).
The thing is, if you look at how biological classification works, from life, domain, kingdom, phylum, class, order, family, genus and species, you can see how close together some things are (lions and tigers etc) and how far apart others are (chicken and tuna - I'm hungry so this was the first thing that popped in my head). This then makes it easy to see why some things are able to reproduce semi-successfully (ligers, mules) and some things can't even though they look similar, why life in Australia is so different, why you have things like hippos that have legs but spend most of their time in water, things that need to breathe air but live underweater etc etc.
Nothing explains why we have such a diversity of life on this planet better.