while studying for his doctorate, washburn received his first opportunity to engage in fieldwork. he served as an assistant zoologist in harold j. coolidge's 1935–1936 asiatic primate expedition. in malaysia he helped collect specimens of various species of colobine and macaque monkeys and the orangutan. in sri lanka and thailand he also collected specimens of lar gibbon and observed their behavior in natural surroundings. he continued this work on the collection when he returned to harvard, at times assisted by gabriel lasker. washburn would later credit the ongoing discussions between lasker and himself during this period (1938) as formative to his views about human variability. to washburn, human variability was to be understood in terms of population genetics, and not according to the terms of racial and constitutional typology as typified by his doctoral advisor, hooton.