Thinking about Barlach made me curious to know more about the Expressionist sculptors.
So far as I know the first Expressionist sculptor was Rodin, a Frenchman. For Rodin nature was a starting point but it always had to be modified by human bias. You could argue that sculpture was always like that but Rodin added exploration and risk and performance. Even humor.
Rodin worked in clay, marble and bronze but lots of later German sculptors preferred wood. Maybe that's because their African influences worked in that medium. Maybe it's because wood was cheap and the artists were poor. One sculptor (Kirchner, above) said he liked wood because the process of carving and creation were visible on the finished piece for all to see. Conventional sculpture was worked in clay and handed off to others
for casting. Only in wood could you say that the final product was produced by a single mind.
Incidentally, I like the way Kirchner frequently photographed his sculptures (above) against painted patterns.
For all its beauty there's something wild and almost unhinged about early German Expressionism, as if the artists who did it were crazy or under a lot of stress. It was an odd discipline because in its early stage it seemed incapable of expressing happiness or sentimentality.
I don't know of any other medium that deliberately excluded a whole range of human emotion. Even so, there are ideas and insights it would be difficult to express if that kind of art didn't exist.
In order to illustrate this point I had to use a painting rather than sculpture. That's because sculpture rarely succeeded in isolating the negative emotions as well as painting. The same might be said of early Expressionist architecture. The first examples were somber and horrific (above).
Later the medium evolved into something that could convey humor and fun.