Can my cousin copyright his world population cartogram?

My cousin made a cartogram depicting world population in microsoft paint.

It became quite popular and he he was contacted by the author of an earlier world population cartogram.

The author of the early cartogram insisted that my cousin's work violated his copyright. My cousin acquiesced and listed the earlier author as the copyright holder of the newer map.

It seems wrong to me. My cousin's work seems original. But the lawyer at his university said that it is not. Who is right?