Afterwards, he studied Zoology, and Genetics in the Faculty of Natural Sciences at the Humboldt University of Berlin, where he completed his PhD in 1927.
Among his important scientific publications were advances in the understanding of sex-determination systems, carcinogenesis, constructive and regressive evolution, genetics of house pets, zoological geography, and species classification.
His research interests and fields of study widened considerably once he arrived in Turkey, and was able to found an entire department from the ground up.
Completing his bachelor's degree at the University of Berlin, in the mid-1920s, he began to study for a PhD in genetics under Professor Erwin Bauer.
In this year, he published his doctoral research work as The Gene in Foreign Genotypes (German: Das Gen in fremder Erbmasse).
He had conducted experiments with cyprinodonts, which were groundbreaking in the field of genetics, which "anticipated the concept now known as gene transfer in carcinogenesis.
Part of his duties included lecturing NSDAP party members and groups of interested citizens about genetics and racial anthropology (called Rassenkunde).
[10] In November 1933, Kosswig joined the SS[11] (see note for possible reasons), an elite branch of the NSDAP (Nazi Party).
The head of the Munster Zoology Department, Professor von Ubisch, was half-Jewish and seen as politically unreliable.
After a long controversy, Ubisch was finally dismissed from his post as head of the Zoology Department at Munster University in 1935, after which he emigrated to Norway.
[13] He also started thinking about leaving Germany itself, which he did in autumn 1937 at the invitation of the University of Istanbul and some German professors, who were already there.
His output was prolific in his Turkish years, with hundreds of articles published, and an entire major university department being built around him at Istanbul.
The Zoology Department at the University of Istanbul, which still exists today, is considered to have been entirely founded by Curt Kosswig.
He oversaw its expansion and "collected examples of mammals, birds, reptiles, frogs, fish and various invertebrates, which he brought in the museum contributing to its enrichment."
[2] Kosswig discovered, identified, and named many new species in this time, including the rare Saz Baligi which means "reed fish" (Garra kemali) and Gölçük toothcarp (Aphanius splendens).
On 8 April 1982, he was buried in the Aşiyan Asri Cemetery following a ceremony held in the Central Building of Istanbul University.