He studied at the universities of Kiel, Freiburg, and Berlin, receiving his doctorate at Kiel in 1895. Following graduation he lived and worked in Karlsruhe, Plymouth, Naples, Cold Spring Harbour (Long Island N.Y.), and Würzburg. From 1901 he worked as a curator for a year at the Selangor State Museum in Kuala Lumpur, afterwards returning to Europe, where he spent another year in Naples.
He was a member of the Hamburg Südsee-Expedition (1908-10) during its first year in Oceania, of which, he collected specimens on behalf of the Hamburg Zoological Museum. From 1928 onward, he worked as a curator and professor at the Museum. In 1939 he became an honorary member of the American Society of Ichthyologists and Herpetologists.
In 1904 he described the Harlequin rasbora, Trigonostigma heteromorpha, a fish species that inhabits the forest streams of Southeast Asia. Taxa with the specific epithet of dunckeri honor his name, such as:
- Barbodes dunckeri (Ahl 1929), sometimes referred to as a bigspot barb.
- Phallostethus dunckeri (Regan 1913).
- Solegnathus dunckeri (Whitley, 1927), sometimes referred to as Duncker's pipehorse.
- Die Fische der malayischen Halbinsel, In: Mitteilungen aus dem Naturhistorischen Museum in Hamburg, volume 21 (1904) – Fish of the Malay Peninsula.
- Die Gattungen der Syngnathidae, In: Mitteilungen aus dem Naturhistorischen Museum in Hamburg, volume 19 (1912) – Genera of the family Syngnathidae.
- Duncker, (Paul) Georg (Egmont) Nationaal Herbarium Nederland
- "Statement based on translated text from an equivalent article at the German Wikipedia".
- Trigonostigma heteromorpha FishBase
- Solegnathus dunckeri Whitley, 1927 GBIF.org
- The ETYFish Project Archived 2015-07-21 at the Wayback Machine. Order CYPRINIFORMES: Family CYPRINIDAE
- Full text of "Proceedings of the California Academy of Sciences"
- Biodiversity Library Book titles